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General Discussions => Truth Table => Topic started by: rkn80 on September 20, 2009, 07:19:08 AM

Title: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 20, 2009, 07:19:08 AM
Hello,

this is my first post on this great forum but I was already reading here for a long time.
Let me first introduce myself a little bit: My name ist Raphael and I'm a young electrical engineer from Germany.
My idea is to build a AD/DA box like the Alpha-Link from SSL, the ADA8000 from Behringer, the i/o boxes from Digidesign and similar. But my system should be more flexible. So that you can populate the box with the number of DACs and ADCs you need and later you have the option to add more channels.
So I started with designing the PCBs of the DAC and of the ADC. Both are already done and I'm going to order first prototypes of the PCB.
The DAC is based on a TI PCM4104 and you have 4 channels per PCB. Each channel offers a fully balanced floating output like the topology presented by G.D. Pontis. The DACs do run completely in hardware mode so that no additional microcontroller is needed but there is an option to control it via the SPI-interface if wanted.
The ADC is based on a TI PCM4202 and supports two channels per PCB. You can either connect a a line level signal or directly a microphone (with or without phantom power). The front end of the ADC is built like the mic design of Cohen but instead of going to the outside the outputs are going directly into the ADC. The idea is that you do not need an extra box for the micamps. Again the ADC is fully hw-controlled.
Both PCBs support I2S input/output.
The next step is to design a ADAT Lightpipe input/output card so that you can connect the box to a PC or whatever as long as it supports an ADAT interface.
The modular design will allow to add other interfaces or to upgrade the box with higher performance AD/DA later.
I would like to share the design with you and perhaps there are people how have an idea for another module or want to design a pcb that offers an additional feature and that can be integrated into the box. If so I invite you to take part in this project.
So is there interest in this project?
I'm also willing to organize a group buy of the DA or/and the AD pcb if wanted.

Raphael  
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ricothetroll on September 20, 2009, 07:31:15 AM
Hi Raphael,

I'm interrested ! Those last weeks I started to take a look at how I could do that kind of project. But I'm no electronic ingeneer, so I had a lot of infos missing, and of knowledges to get to do that project properly.

I'm not so sure I can help for the theorical part, but I make homemade PCBs, if ever that's helpful...

I'd be curious to take a look at the schematics !

Pretty cool project indeed ! Congratulations !
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on September 20, 2009, 10:05:12 AM
Raphael - welcome to the board:)

Your project sound awesome. I look forward to reading how this evolves.

Kindest
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on September 20, 2009, 10:58:48 AM
Interesting plan. Welcome.

Traditionally one of the more difficult things to get right is clock synchronization to external WC sources without generating excessive jitter; in a modular design clock distribution can be challenging too.

Have you seen this older thread (http://www.groupdiy.com/index.php?topic=11498.0), BTW?

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: volker on September 20, 2009, 11:02:12 AM
Hi Raphael,

I've been thinking about something similar lately. Personally I would prefer to keep the ADC inputs just line level without an additional mic preamp, but keeping it modular is the great thing about it. I'm going to check out the converters you're using... Would be cool to see the schematics.


Gruß, Volker
Title: Re: Modular multi channel DIY AD/DA Box
Post by: pedroplanet on September 20, 2009, 11:10:06 AM
very interested on build one  ;D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on September 20, 2009, 01:13:31 PM
Wow. You have my attention... hah
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 20, 2009, 05:09:57 PM
Well, the idea is to make something like an active busplane with buffers on it for the clock lines. Every module runs as a slave so that the intra-module clock lines are isolated from the system wide clocklines via buffers.
In the first step I will select one of the ADs as a master providing the system with the needed clocks. Later that can be changed with an additional module that also offers a word clock sync to the outside.
In the next days I'll publish the schematics step by step. I need to make them nice first. ;)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on September 20, 2009, 05:33:22 PM
Well, the idea is to make something like an active busplane with buffers on it for the clock lines. Every module runs as a slave so that the intra-module clock lines are isolated from the system wide clocklines via buffers.

Keep in mind that every layer of buffering increases jitter, and that even low levels of power/ground noise can have significant impact on clock integrity.

Looking forward to seeing your schematics,

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuc224 on September 20, 2009, 06:40:13 PM
WOW!! got my attention as well, the DAC chips look good, is there any reason that you didnt choose the PCM 4222 for AD? Those chips are about as good as they get! i heard a shootout between the lavry gold mk3 and the PCM 4222EVM and to be totally honest, they both sounded great, extreme clarity, great depth and both true to source. One wasnt better than the other it was mostly subjective. But considering that the lavry gold is 7500 and the pcm4222 is 149...........
Title: Re: Modular multi channel DIY AD/DA Box
Post by: playboss on September 20, 2009, 07:27:46 PM
dont use 4222 but 4220... The number 4222 asks for trouble already...
The difference is in feature set , 222 is unlikely as hell .
How are you doing clock distribution? Clock on seperate daughterboard would be preferable.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuc224 on September 20, 2009, 09:31:30 PM
Could you explain? Everything on the 4222 is new and up to date.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Whoops on September 20, 2009, 10:24:15 PM
I think you have a great project!

and I don't think there's anything similar in this forum anyway.

I'm also in favour of a Line level input, instead of Mic Pre.
People here have already done their favourite Mic Pres, Neve type, API, SSL, etc, so
it would be great to keep the signal flow as simple as possible after the Mic Pre.


Title: Re: Modular multi channel DIY AD/DA Box
Post by: playboss on September 21, 2009, 01:27:13 AM
Could you explain?

No.

Since you compared an evm without psu to a Lavry converter I have nothing on earth to explain.  >:(
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on September 21, 2009, 02:08:20 AM
Could you explain?

No.

Since you compared an evm without psu to a Lavry converter I have nothing on earth to explain.  >:(


Playboss - what gives man? Why the attitude?  If you believe somebody has some wrong information share your views rather than being heavy about it.

Title: Re: Modular multi channel DIY AD/DA Box
Post by: playboss on September 21, 2009, 02:32:15 AM
ok.
So, you guys need DSD output and 6bit quantizer output pins, thats all what 4222 gives over the 4220 . Fine, nice job.

These people who bought all these EVM's dont get the idea of these type of converters, that is , these are more like set of digital signal processing algo's than anything """analog""".
-You bought the 4222 evm, you bought a set of preset algorithms and a cheap analog front end. Now you can configure it with jumpers and leaves you with a lot of useless features,  like , DSD, flat dithered 16bit PCM out.

Comparing this to a Lavry is like , taking 1 preset of a cheap synthetiser against a vast array of presets on the expensive Lavry
- and you're free to tweak it too. It will give you a 16bit 96khz output that kills the 24/96 of the 4222 evm and its hacked power supply.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: promixe on September 21, 2009, 03:25:18 PM
Let's not get all hostile here. =) While I personally think there is no comparison between the Lavry Gold series AD and a "chip converter" whatever it might be, I also think that PCM4222 is a great AD chip and it sounds awesome, so does the 4220. Also, the 4222 has -124dB SNR, which is one dB more (eventhough I think they measured it A-weighted) over 4220. But of course the argument here is - "if you REALLY know what you're doing you might get into the <-120dB spec, otherwise the noise floor of your system is gonna be above the ADC spec". =)

But I would too encourage to have the AD design based on either 4220 or 4222 and not the older 4202 series.

PS: Lavry Gold AD has an analog filter upfront (chopping everything above Nyquist beforehand) followed by custom precision laser trimmed resistor network to perform the conversion and what he calls "digital soft saturation" that sounds like nothing else out there if clipped. Most of silicon ADC chips these days have basic FIR decimation filters post the conversion that are pretty basic, and while giving near linear phase on the output (especially 422x family) it doesn't sound nearly as good as true analog filter. That's where a clear advantage of 4222 would come in with its 6-bit modulator outputs to bypass internal FIR and design your own superb decimation filter in a DSP. But I don't this particular project would require such steps. Basic 4220 will sound fine. =)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Matthew Jacobs on September 21, 2009, 03:59:49 PM
I'm hooked as well. This is exactly what I need. Can't help much on the digital side but will definitely support this project.

I vote for line inputs as well.

Nice one Raphael!

J
Title: Re: Modular multi channel DIY AD/DA Box
Post by: detonator on September 21, 2009, 04:23:14 PM
Regarding to my post  http://www.groupdiy.com/index.php?topic=35441.0 (http://www.groupdiy.com/index.php?topic=35441.0) this is one I'm looking forward to. It's not always a matter of coming up with new designs, but a different approach for a concept is a way to go. So count me in.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bitman on September 21, 2009, 04:25:08 PM
I have a stuffed lightpipe board that I bought from someone on this board but never used it.
You might like it for prototyping.

$25.00

ron AT mtrecording DOT com
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuc224 on September 22, 2009, 12:39:36 AM
I really didnt mean to offend anyone by my comments :( , im just going by what i heard from the samples posted. I gave an unbiased opinion on what ive heard. The lavry gold is one of the finest converters made, but what i heard was almost as good.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: pedroplanet on September 22, 2009, 09:23:14 AM
I vote for line level! ;D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 22, 2009, 05:12:05 PM
Ok, to make some progress, here is the schematic of the DAC module. Please note, that the values of the output filters are not correct and that I used the NE5532 but you can also use another opamp that comes with the same pinout. I think I'll use the AD8620.
I'm now going to order prototypes of the DAC pcbs as soon as I have found a good source for the PCM4104 in small quantities.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on September 22, 2009, 08:54:32 PM
I'm now going to order prototypes of the DAC pcbs as soon as I have found a good source for the PCM4104 in small quantities.

A big part of the performance will be in the layout; if you post it you could get some useful feedback.

Sources for the PCM4104 include Digi-Key and Mouser; please put your location in your profile for possible local suppliers.

JDB.
[and there's always TI's samples program]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 23, 2009, 03:20:03 AM
The layout I'll post today evening when I'm back at home.
I tried the TI sample program but they do not sample the PCM4104.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 23, 2009, 07:00:55 AM
What a luck: I just remembered that I've the pcb project on my MacBook too, so here is the layout of one DAC module (4channels).

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on September 23, 2009, 08:46:55 AM
here is the layout of one DAC module (4channels).

Looks quite reasonable. The only issues I have are relatively minor:

- the +5VA trace running under the chip makes a nasty moat in the ground plane. I would suggest either stitching the top-layer ground under the chip to the plane with a few vias, or even using a single jumper wire and keeping the ground plane unbroken (ugly but functional).
- I wonder what happens wrt ground loops given that you have grounds connected at both X101 and X1001
- consider removing some of the ground plane right below the inputs of the op-amps and their associated traces, this will help stability especially with faster op-amps.
- those capacitors marked X7R will be C0G/NP0 in the final version, right?
- the MCLK trace is relatively long and unshielded
- you may want to directly connect the ground on C1018 to the ground side of IC1002

Other than that only a test will show its performance. It looks interesting, but definitely not a soldering project for the average DIYer.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 23, 2009, 09:25:01 AM
- the +5VA trace running under the chip makes a nasty moat in the ground plane. I would suggest either stitching the top-layer ground under the chip to the plane with a few vias, or even using a single jumper wire and keeping the ground plane unbroken (ugly but functional).
Yes, routing the +5VA was/is a problem on a two-layer design. First I routed it under the balanced output lines, but then the analogue outputs a crossing a split in the ground plane. So I decided to place a copper plane under the chip on the top layer und to run the 5VA tracks under the chip on the bottom layer.

- I wonder what happens wrt ground loops given that you have grounds connected at both X101 and X1001
The reason that you have gnd lines on both connectors is that you then can connect flatband ribbon cables without using a mainboard, you can go directly to a sub-d or XLR connectors. Indeed if you want to plug in this module in a mainboard you have to make sure that you are not making ground loops. So think of it like offering an additional option.

- consider removing some of the ground plane right below the inputs of the op-amps and their associated traces, this will help stability especially with faster op-amps.
Never seen that on a solid ground plane.

- those capacitors marked X7R will be C0G/NP0 in the final version, right?
Yes. As I said the values in the filter are not correct. I simply used what I found in my component library. :)

It looks interesting, but definitely not a soldering project for the average DIYer.

Hey, come on. Its only 0805 and TQFP. My first soldering projects have been already made with these case types. It is not so difficult like it seems to be. You need to know two or three tricks. :)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on September 23, 2009, 09:49:22 AM
- consider removing some of the ground plane right below the inputs of the op-amps and their associated traces, this will help stability especially with faster op-amps.
Never seen that on a solid ground plane.

For some of the faster op-amps that some people like to use for audio work nowadays it is pretty much required. Have a look at the TPA6120A2 data sheet (http://www.ti.com/lit/gpn/tpa6120a2) starting at page 16 for a brief explanation. (I know that the '6120 won't fit on your board, but the theory remains the same, and applies to both VFB and CFB amps).

For 5532-class op-amps this is generally not necessary (depending on topology, layout and impedances, of course).

It looks interesting, but definitely not a soldering project for the average DIYer.

Hey, come on. Its only 0805 and TQFP. My first soldering projects have been already made with these case types. It is not so difficult like it seems to be. You need to know two or three tricks. :)

I know that you can do quite a bit (http://www.groupdiy.com/index.php?topic=30868.msg374360#msg374360) with minimal tools and not too much effort, but recent discussions (http://www.groupdiy.com/index.php?topic=34590.0) show that many people are still quite cautious toward even simple SMD work. Besides that, your board doesn't make life extremely easy: the pads of the passives don't look to be too large, in some areas the passives are packed rather tightly (good for performance, bad for novices). I'm not new to SMD work, but I still hate hand-soldering D-PAK/TO-252 parts like your voltage regulator.

JDB.
[could be worse, could be a TO-263 on a nice big thermal plane. Brrrr....]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: pedroplanet on September 23, 2009, 09:58:51 AM
It could be less SMD and more Diy friendly, I think i won't be able do build one  :'(
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 23, 2009, 11:07:36 AM
Why so pessimistic? Soldering the passive parts is not more diffcult then wired parts. It is even fast because you do not need to prepare the wires etc... The only thing, that is a littlebit difficult is the DAC but there is no way around because you can only buy it in this package.
I do all my DIY stuff in SMD and I like it. If you etch the PCB by yourself you save a lot of drilling work and you win a more solid ground plane.
I think, I'll make an instruction manual when I'm building the prototype to support people who are scared by SMD. ;) I've no special tools for it. I only use a solder iron with a small tip and that works quite fine.
I agree it becomes very hard or impossible when we want to use BGA or packages without exposed pins. But these types I normally avoid because I know that I cannot solder them myself.  ::)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on September 23, 2009, 12:08:58 PM
I agree it becomes very hard or impossible when we want to use BGA or packages without exposed pins. But these types I normally avoid because I know that I cannot solder them myself.  ::)

Sure you can. Just use solder paste, a stencil and an oven or a hot plate.

JDB.
[and people have etched their own stencils, too, although considering the cost of the parts I prefer buying laser-cut stencils]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: iangomes on September 23, 2009, 12:41:24 PM
if this project really gets going, I may be of some help... my father owns a circuit board manufacturing company (which I have worked in), with solder paste screening, pick and place machines, and a couple of reflow ovens.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Michael Tibes on September 23, 2009, 01:30:30 PM
if this project really gets going, I may be of some help... my father owns a circuit board manufacturing company (which I have worked in), with solder paste screening, pick and place machines, and a couple of reflow ovens.
This migth be cool, if it is not too expensive. Anyway, soldering is not the most fun part of dying for me, I might be happy to purchase some prepared boards.

Michael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 23, 2009, 02:55:19 PM
I'm sure that there is a way to arrange that.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Matthew Jacobs on September 23, 2009, 04:07:16 PM
I haven't soldered SMDs yet. But for this fantastic project, I'll definitely give it a go.

J
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on September 24, 2009, 04:36:08 AM

Yep - very excited to see how this one develops :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 24, 2009, 11:46:43 AM
I made some minor changes on the layout (gnd vias now without thermal relief etc.) and ordered the first prototype board of the DAC today. It should arrive in 8days.

I'm think of making a ADAT input board first before releasing the ADC  board because then there is already use for some people: You can put the board together to make a nice multi-channel DA converter. What do you think?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: flaheu on September 24, 2009, 12:18:50 PM
This project looks very nice !
I'm definitevely interested in DA with adat with nice ouput opamps, cheap and reliable.
What would be nice also is to balance via That Chip to the outside world (with a nice output TX behind it, it's just creamier !)

Cheers
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Matthew Jacobs on September 24, 2009, 08:31:33 PM
Yeah, Adat is perfect.

I got a RME adat sound card with 3X 8 light pipe input/output, I've been waiting for ages for a DIY converter project.  I will definitely need some of these boards...

Thanks Raphael.

J
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mylesgm on September 25, 2009, 01:27:41 AM
What about aes I/o? Would allow for higher sample rates and connection to aurora's, hd192's etc
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 25, 2009, 10:00:17 AM
Well, that's why I decided to make it modular. The pinlayout of the modules will be published (for the DAC you see it in the schematic). I'm thinking of making something like a standard connection and so that everybody can design modules for it, a kind of open hardware  ::)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: snipsnip on September 25, 2009, 10:44:00 AM
Very interesting project - looks great so far. Cant wait to see more!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 01, 2009, 06:50:13 AM
Hi,

to keep this thread alive: The PCB company informed me that the prototype pcb of the DAC is shipped today.
So if everything goes well I can stuff the board over the weekend and test it.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuc224 on October 01, 2009, 09:11:01 PM
Im really interested in this project :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on October 01, 2009, 09:36:04 PM
rkn80, you're a good man for sharing this project with the forum! I also vote for line ins on the ADC... :D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 02, 2009, 07:39:23 AM
Today the pcb and the parts arrived. :)
As you can see on the picture I placed 6 of the modules on one pcb because I need 24 output channels. That was cheaper then ordering 6 modules as prototypes. So I can use the weekend to stuff the board and to test it.

Raphael

Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on October 02, 2009, 08:02:45 AM
That looks quite nice. What are you planning to use to drive it on the digital side?

Happy soldering,

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 02, 2009, 09:02:27 AM
The inputs on every module are I2S. For the first run I'll connect it to a SHARC evaluation board because their I've direct access to I2S outputs. If successful I'll then proceed with making an ADAT interface (3x lightpipe = 24 channels) that I can connect it to an RME Hammerfall.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Matthew Jacobs on October 02, 2009, 05:33:29 PM
Cool, I got a RME Hammerfall as well  ;D

Nice to see you got the proto boards. Good luck with the soldering.

J
Title: Re: Modular multi channel DIY AD/DA Box
Post by: crisotop on October 03, 2009, 04:25:47 AM
Sorry if I missed this - but what about 88/96k SMUX over ADAT? Is this something doable?

cheers
Christoph
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 04, 2009, 01:32:56 PM
Just to let you know, I've successfully build the first module with 4 channels running. A signal was sent via an ADC->i2s into my DAC board and I was able to see the signal on the outputs with an oscilloscope.
I've to leave now, later this evening I'll post some pictures of the prototype, I think you want to see it. :D

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 04, 2009, 03:13:57 PM
Here is a picture how the board looks after stuffing it (except the pinheaders).

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 04, 2009, 03:34:48 PM
And here under test conditions. The SMD soldering was done by hand with a standard solder iron. No special tools for SMDs were used. So, don't say it is not possible to do it yourself. It is and it is much easier then it looks and faster then wired parts. :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Matthew Jacobs on October 04, 2009, 07:16:35 PM
Nice!!!

The SMD resistors I can understand, but the big chip? Did you solder that by hand as well... that's cool....

I'm planing on building more digital stuff so I'll be interested to know any tips and tricks you have on soldering those chips.

Nice work Raphael.

J
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on October 05, 2009, 12:35:02 AM
The inputs on every module are I2S. For the first run I'll connect it to a SHARC evaluation board because their I've direct access to I2S outputs. If successful I'll then proceed with making an ADAT interface (3x lightpipe = 24 channels) that I can connect it to an RME Hammerfall.

What are you going to use for the ADAT interface? The obvious choice is the Wavefront part but I don't know if they sell small quantities.

I have an ADAT transmitter design in VHDL. One day I'll actually test it.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 05, 2009, 06:55:04 AM
The SMD resistors I can understand, but the big chip? Did you solder that by hand as well... that's cool....

I'm planing on building more digital stuff so I'll be interested to know any tips and tricks you have on soldering those chips.

Indeed there is a trick for those chips. I learned it while I was working for a company making audio electronics: You have to clean the pads from tin-solder with desoldering wick if the pcb company tin-coated the pads so that they are really planar. Then you put the chip on it and make to solder points on opposited sides. The chip is now fixed and the pins should be on the pads. Then you start on one non-fixed side and put a lot  of tin-solder on the pads/pins like you want to make a big shortening over all pins. You do that on all sides. In the last step you heat up the tin-solder again but now you move carefully the solder iron parallel to the case side, the tin-solder will follow the iron and free the space between the pins. At the end you can remove the big tin-solder lump with your desoldering pump. Repeat that on all sides. You have to be careful that you you do not deform the pins but it works fine and at the end you have nicely soldered the chip on your pcb. Finally you have to inspect all sides (with a loupe if your eyes ar enot so good) if there are still some shortenings. If so you can easily remove them with the solder iron because the tin-solder will flow to the pins and pads and free the space between the pins. (I forgot the name of the physical phenomen that causes this behaviour).
That's it. With this method I had already success when I tried it the first time: A TSOP case and after doing that two or three times you'll find it easy to do.
Well it sounds a little bit complicated perhaps I should make some pictures when I do it for the other DAC chips. :)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 05, 2009, 07:01:51 AM

What are you going to use for the ADAT interface? The obvious choice is the Wavefront part but I don't know if they sell small quantities.

I have an ADAT transmitter design in VHDL. One day I'll actually test it.

-a

Yes, I want to use the Wavefront parts. The main reason is that I want to avoid the need for programming devices. I think most people (including me) do not have the stuff to program a fpga. I know that there are some free fpga designs for ADAT (and other protcols). But if you are willing to do that, go head. Put a pin header on your board that has the same pin layout like my dac board and you can connect it easily to my DAC pcb. :)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Matthew Jacobs on October 05, 2009, 03:47:13 PM
Thanks Raphael for the soldering tips, makes a lot of sense. Sounds pretty easy to do as well. Some close up pictures would help if you get the time of course.

Are your boards complete? have you tested them yet?

J
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 06, 2009, 05:13:03 PM
Well, I tested the 4 channels you can see populated on the picture. They are working so far. Today evening I tuned some filter componentes for a good frequency response. Btw. the DACs give now a maximum output voltage swing of ~21dBu (adjustable via resistor selection).

I see that there are different thoughts about the digital inputs. All of the mentioned the formats are possible as soon as a board is designed for it. Again I'll first go for ADAT (48kHz and 96kHz SMUX) so if someone is willing to design an AES/SPDIF board you're welcome.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ask on October 06, 2009, 06:04:30 PM
very nice! ::)


Well, I tested the 4 channels you can see populated on the picture. They are working so far. Today evening I tuned some filter componentes for a good frequency response. Btw. the DACs give now a maximum output voltage swing of ~21dBu (adjustable via resistor selection).

I see that there are different thoughts about the digital inputs. All of the mentioned the formats are possible as soon as a board is designed for it. Again I'll first go for ADAT (48kHz and 96kHz SMUX) so if someone is willing to design an AES/SPDIF board you're welcome.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 08, 2009, 05:41:48 AM
Yesterday evening I tried to measure the THD+N. Too bad, with my Presouns Firebox I'm not able to measure it, the THD+N of the Firebox is already too high (or the THD+N of the PCM4104-board is too low... ;) ). Any ideas how to measure it wihout very expensive tools?
When the AD-pcb is there I can measure it for the combination of my AD/DA board because then I can go into it and out of it digital via S/P-DIF.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on October 08, 2009, 06:21:28 AM
This looks amazing but miniaturized SMD for all the analog components? A version with through-holes would allow all the great parts we know and easier work flow for most of us.

I'd just be overjoyed at through-hole PCBs.

If the circuit works, maybe someone can print another PCB layout of the same circuit with through-hole for those of us who want it?

Also, in terms of features, I'd like line in ADC and would vote for higher spec adc/dac chips as well if possible. A word clock in BNC sync will also be good.

But mostly I want through hole components.  ;D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Moby on October 08, 2009, 06:42:48 AM
Great Raphael. I notice your thread today and it looks promising. I don't see any problem with DIY SMD if U use magnifier glass and good soldering tip  ;D BTW, AES/EBU board will be great . Just stay sharp mate 8)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 08, 2009, 07:59:53 AM
This looks amazing but miniaturized SMD for all the analog components? A version with through-holes would allow all the great parts we know and easier work flow for most of us.

... and would vote for higher spec adc/dac chips as well if possible ...

To be honest I wanted to keep the project at a good cost/performance ration in the first step. Of course you can use a AD1955 or a PCM179x but these chips are much more expensive for just 3dB additional SNR or whatever. So I decided because I need for myself 24channels to use the PCM4104 for now. Same thoughts on the ADC. Two PCM4204 are cheaper then a CS5368 or some PCM4220s.
Besides that SMDs are good for the performance they're cost reducing. Interestingly the SMD components from my distributors are cheaper then the equivalent through-holes and SMDs are space saving on the pcb. That reduces pcb production costs. :D

If the circuit works, maybe someone can print another PCB layout of the same circuit with through-hole for those of us who want it?
If so I'd be pleased to provide the volunteer with the design files. if helpful.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bernbrue on October 08, 2009, 09:02:28 AM
Hi Raphael,
very interesting project. Great work! I really admire the "straight forward" way you introduced your project here in prod pro.
@all: may I suggest to let Raphael finish his project the way he wants to do it. The converter board seems to be very versatile and open for quite a lot of options to be implemented. Concerning SMD Raphael gave a lot of hints how to solder these parts. I never worked with SMD but I´m willing to learn and to try. I agree with Raphael to aim for a good cost/performance ratio, otherwise it wouldn´t make sense to DIY a ADC/DAC.
 
Go on, Raphael

regards
Bernd
Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on October 08, 2009, 05:32:54 PM

To be honest I wanted to keep the project at a good cost/performance ration in the first step. Of course you can use a AD1955 or a PCM179x but these chips are much more expensive for just 3dB additional SNR or whatever. So I decided because I need for myself 24channels to use the PCM4104 for now. Same thoughts on the ADC. Two PCM4204 are cheaper then a CS5368 or some PCM4220s.
Besides that SMDs are good for the performance they're cost reducing. Interestingly the SMD components from my distributors are cheaper then the equivalent through-holes and SMDs are space saving on the pcb. That reduces pcb production costs. :D

If the circuit works, maybe someone can print another PCB layout of the same circuit with through-hole for those of us who want it?
If so I'd be pleased to provide the volunteer with the design files. if helpful.

Raphael

That sounds great Raphael. I understand about your converter chips - they still spec very well and should be quite affordable. As for SMD vs through-hole, I've been looking around and SMD should actually be okay. I'm warming to it.

Personally, I could use 32-48 d/a + 16 a/d, so this project is very much of interest to me and I'm sure a lot of others here as well. Thanks for all your hard work so far. :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: radiance on October 08, 2009, 05:58:41 PM
Yesterday evening I tried to measure the THD+N. Too bad, with my Presouns Firebox I'm not able to measure it, the THD+N of the Firebox is already too high (or the THD+N of the PCM4104-board is too low... ;) ). Any ideas how to measure it wihout very expensive tools?
When the AD-pcb is there I can measure it for the combination of my AD/DA board because then I can go into it and out of it digital via S/P-DIF.

Raphael

Just boost the signal somewhere along the line...or in you DAW ...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: skipwave on October 09, 2009, 12:41:50 AM
It is and it is much easier then it looks and faster then wired parts. :)

It is very DIY-able. Just get a nice little clip and posable holder thing-y. Magnifying glass also helps. Then just tin, stick, repeat.  ;D

Very interested to see this project continue to develop.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 12, 2009, 02:23:14 AM
Here is a link which explains how to solder SMD ICs with standard tools. It is in German but I think the pictures and the youtube clip are self-explaining:

http://thomaspfeifer.net/smd_loeten_tsop.htm (http://thomaspfeifer.net/smd_loeten_tsop.htm)

Raphael

Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on October 12, 2009, 03:43:54 PM
Translated to English:
http://www.translate.google.com/translate?hl=en&sl=de&tl=en&u=http%3A%2F%2Fthomaspfeifer.net%2Fsmd_loeten_tsop.htm

Also a tonne of help here:
http://www.curiousinventor.com/guides/Surface_Mount_Soldering

(http://www.gearslutz.com/board/images/smilies/thumb.gif)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mainmachine on October 13, 2009, 03:32:48 PM
After watching that, I am ordering some liquid and paste flux, and I would like to express my interest in this project.

rkn80- count me in on the group buy! I'd like to try 8 channels of these converters, but I'll go in for up to 32 if it'll bring the costs down per board. How many people are in on this? What are the price breaks on ordering these boards?


Also a tonne of help here:
http://www.curiousinventor.com/guides/Surface_Mount_Soldering

(http://www.gearslutz.com/board/images/smilies/thumb.gif)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on October 13, 2009, 03:57:19 PM
The surface mount stuff still kind of scares my 47 year old hands...

But, I'd be down for 16 channels of D-A with an ADAT SMUX Interface.

Nothing like jumping in with both feet. :)

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: syn on October 13, 2009, 04:18:36 PM
 :o
I'm in.
Any idea of the prices?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on October 13, 2009, 04:46:31 PM
This sounds cool. I'd love to give it a bash with 24 in, 24 out.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mainmachine on October 13, 2009, 07:59:48 PM
If the performance of these converters warrants, a group buy for SOIC-8 dual opamps, PCM4104, PCM4204 and all the other components would be in order. Prices get pretty nice at 100+ parts, and due to the repetitive nature of this project (lots of parallel, identical channels) the numbers add up fast.

16 channels x 4 dual opamps = 64 peices, so if 8 people are building 16 ch. units we're at 500 piece pricing for the opamps, 100 piece price for the A/D and D/A chips- these could be very inexpensive!

I'd be leaning towards BB OPA2604 opamps- any input?

I'm probably getting ahead of the project here, but I'm psyched at the prospect of lots of channels of good sounding A/D/A conversion!

-Dave
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on October 13, 2009, 08:03:55 PM
I've been watching this too.  ;)

OPA1612 is the way to go.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on October 13, 2009, 08:20:23 PM
Personally not a big fan of the Burr Browns. I'd prefer Analog Devices opamps like what Raphael mentioned. AD8620, AD8599, AD823, etc.

But I doubt we'd ever all agree on opamps.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 14, 2009, 07:11:14 AM
I agree. We will never find an opamp that we all like! :)

The status of the project is at this moment that most of parts are now mounted on my 24channel prototype DAC pcb. Some resistors and capacitors still to go. Unfortunately I've damaged my solder iron when I wanted to change the tip of it yesterday (the tip is fixed with a srew and this screw is broken :( ). Today I'll buy a new one and hopefully today evening all 24channels will be done.

Regarding a group buy:

I would be happy to organize that. The last price for one 4channel board was ~25Eur if I buy 10 of it (that's why I decided to put 6 boards on one pcb, total cost reduced...). 10 boards is the minimum. If  we have more orders then th eprice will go down. I'm a little bit unsure how to proceed with the group buy. Perhaps I should open a seperate thread in the black market section. That will keep away the ordering things from the technical discussion here. What do you think?

Raphael


 
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bernbrue on October 14, 2009, 09:29:08 AM
Hi Raphael,
open up a new thread (feeler) in BM, that would keep the business out of this thread. I very much appreciate that you want to organize a groupbuy for the components, since you already sourced the parts for your prototype and know where to get the necessary parts. Pcbs and parts in one hand seem to be the best solution. Would it make sense to put together a kit? So everyone can decide, if he wants to buy the pcbs only, pcbs plus parts, maybe a kit with presoldered DAC. I don´t know. Anyway, take your time with prototyping. Personally I think it´s too early to think of  groupbuys and commercial stuff in general. I would also appreciate that your immense efforts to bring this project so far and your decision to share it with us is going to be honored with some extra money, when selling pcbs and parts.
regards
Bernd
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Moby on October 14, 2009, 12:35:59 PM
Quote
open up a new thread (feeler) in BM, that would keep the business out of this thread
Yes, and post link here , than we will know when to react  8)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mainmachine on October 14, 2009, 02:19:42 PM
OPA1612 is the way to go.

I'm liking this one for this job since there's specific mention in the datasheet for use as a D/A buffer.

Personally not a big fan of the Burr Browns. I'd prefer Analog Devices opamps like what Raphael mentioned. AD8620, AD8599, AD823, etc.

But I doubt we'd ever all agree on opamps.

So true! Ideally I'd like to get a few different BB and AD chips to do some A/B comparisons. The multi channel nature of this project will make A/B comparisons *so* easy.

-Dave
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 15, 2009, 02:45:43 AM
So, it is done. Yesterday evening the first 24 dac channels came alive. :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Matthew Jacobs on October 15, 2009, 03:58:06 AM
Yes!!!!!

well done bro!

J
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuc224 on October 15, 2009, 05:33:44 AM
Yeah Raph, I really appreciate u sharing this with us. Id really be in for 24 channels, but would like a presolderd DAC, if it would be possible. Anyhow thank again.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: snipsnip on October 15, 2009, 07:56:08 AM
Congratulations!

How do they sound?

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 15, 2009, 02:49:34 PM
Congratulations!

How do they sound?



Well, they do not sound. :D They simply play what you send to it. ;)
To be honest, I find it a bit hard to describe how they sound. The only thing I can compare to is my Presonus Firebox. I could say that my DAC sounds better then the Firebox but that would not be fair because I think if you build something yourself you'll always find that your self-made unit sounds better because you made it. ;)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: snipsnip on October 15, 2009, 02:55:51 PM
Haha. You know what  I mean!

Would be really great to hear some shootouts. Are these likely to match up to the quality of SSL, Lynx, Apogee etc?

Title: Re: Modular multi channel DIY AD/DA Box
Post by: syn on October 15, 2009, 03:36:08 PM
Congratulations, gret job.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: 0dbfs on October 15, 2009, 06:22:14 PM
This is very cool!

I don't know but I wonder whether using DOA's in a project like this would make any sense?

It would take more space on the board.

Cheers,
jonathan
Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on October 16, 2009, 12:13:46 AM
Put your DOA in front of it. I think the aim here is transparency and accuracy, over a certain "sound)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on October 16, 2009, 12:39:30 AM
Yes I somewhat agree but it may become a sort of summing box issue again where tone/colour v's pristine audio becomes a personal thing and there ends up being no right answer. Some ears may prefer a DOA coloured converter and others will find their ears rather clear as possible leaving their pre-converter gear to do their thing.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on October 16, 2009, 01:39:29 AM
I've contemplated the idea of discrete converters a bit in the past and I think there may be better places to integrate DOA's. 

DOAs are big and expensive so I think it makes sense to put them where they will have the most audible effect. Technically perhaps this may be the ADC/DAC, since everything goes through them. But if the opamps are hardly applying any gain in the circuit, an IC might be near perfectly transparent, and you might be better off saving that discrete $$$ for use in the pres, comps, and perhaps eq's.

I don't know how much gain the opamps will be pushing through a circuit like this, so I don't know if it's even useful to think of it in these terms. But that's the first thought that runs through my head on the subject.

Also, remember this is surface mount, so even if you got some nice dual DIP-8 discrete opamps like Audio-gd OPA-Sun, you'd also have to buy SOIC-DIP adapters and hope the whole Frankenstein holds together without falling off the board. Price would be >$40 per opamp, or literally thousands of dollars for any sizable number of channels.

Considering you can get pretty great surface mount IC's for $5-10 each and they'll fit no problem, it seems like a more efficient way to go. Hopefully it should still sound awesome as well.

Title: Re: Modular multi channel DIY AD/DA Box
Post by: mainmachine on October 16, 2009, 02:34:56 PM
I've contemplated the idea of discrete converters a bit in the past and I think there may be better places to integrate DOA's. 

DOAs are big and expensive so I think it makes sense to put them where they will have the most audible effect. Technically perhaps this may be the ADC/DAC, since everything goes through them. But if the opamps are hardly applying any gain in the circuit, an IC might be near perfectly transparent, and you might be better off saving that discrete $$$ for use in the pres, comps, and perhaps eq's.

I don't know how much gain the opamps will be pushing through a circuit like this, so I don't know if it's even useful to think of it in these terms. But that's the first thought that runs through my head on the subject.

I'm with you on this- since the opamps in this circuit *should* just be acting as buffers/ line drivers, they shouldn't really be adding any gain, so DOA's would be excessive.

-Dave
Title: Re: Modular multi channel DIY AD/DA Box
Post by: living sounds on October 16, 2009, 08:07:27 PM
Well, they do not sound. :D They simply play what you send to it. ;)
To be honest, I find it a bit hard to describe how they sound. The only thing I can compare to is my Presonus Firebox. I could say that my DAC sounds better then the Firebox but that would not be fair because I think if you build something yourself you'll always find that your self-made unit sounds better because you made it. ;)

Raphael

Great project!

Where in Germany are you based? I've got some good converters here to compare it to.

I think the difficult part is to get really low jitter. But as long as the converter is the master in a given setup at least sophisticated reclocking circuitry won't be needed. A very clean power supply is important, too.

Is there a way to configure the converter chips to use minimal filtering, especially no linear phase filters? I'd prefer some phase shift from an analog filter (in both DAC and ADC) to compromises in the impulse response caused by (real time) digital filters. I think one of the reasons for the Lavry Gold's big latency is to minimize these problems.

Gregor
Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on October 16, 2009, 10:28:19 PM
I think the difficult part is to get really low jitter. But as long as the converter is the master in a given setup at least sophisticated reclocking circuitry won't be needed. A very clean power supply is important, too.

As far as word clocking, I am still not sure what we will need or Raphael will be building in.

I think the most economical connection unit for hooking this to your DAW would be the M Audio LightBridge. At $350, each unit can give 16 i/o 24/96 SMUX over firewire or 32 i/o 24/48. And they already feature BNC word clock I/O, so I think you should be able to set Raphael's D/A converters to ADAT slave clocking and send your master sync directly from the LightBridge along the ADAT.

However, I do not think this will work for the ADC's, as they will not sync via ADAT. For those, at a minimum, you will need 1 BNC word clock input per 16 channel unit.

Also, even with the DAC's, a dedicated BNC input is desirable. Many have expressed issues trying to sync via ADAT clocking, so having the choice to clock directly is good.

Will BNC word clock I/O be integrated into the unit design?

Quote
Is there a way to configure the converter chips to use minimal filtering, especially no linear phase filters? I'd prefer some phase shift from an analog filter (in both DAC and ADC) to compromises in the impulse response caused by (real time) digital filters. I think one of the reasons for the Lavry Gold's big latency is to minimize these problems.

That would be very cool. I would love to have some like those if we could.

But I believe it would require a fair amount of added analog circuitry if you want a different analog filter point for each sample rate, unless everyone will agree on a fixed rate of say 96. Plus I imagine the troubleshooting to get that working seamlessly so the ADC isn't being overfiltered or being fed extraneous frequencies from a not steep or low enough filter might be difficult.

A simple optional set-frequency LPF (eg. 70-90 kHz) in the signal flow might work if the chips can be so configured.

But anyway, it sounds like Raphael's already pulling it together pretty fast. So I think as long as it works, I'll be satisfied.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: living sounds on October 17, 2009, 05:46:16 AM
But I believe it would require a fair amount of added analog circuitry if you want a different analog filter point for each sample rate, unless everyone will agree on a fixed rate of say 96. Plus I imagine the troubleshooting to get that working seamlessly so the ADC isn't being overfiltered or being fed extraneous frequencies from a not steep or low enough filter might be difficult.

A simple optional set-frequency LPF (eg. 70-90 kHz) in the signal flow might work if the chips can be so configured.

An analog filter that works for 44,1 khz (= 20-22khz) should suffice IMO. The additional high frequency content at higher sample rates isn't imporant anyway. At least the benefit from an analog filter (opposed to a digital one) would be greater than the loss of ultratrasonics caused by the fixed filter IMO.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 20, 2009, 03:20:15 AM
Hi,

sorry the project was delayed for some days now due to a lot of work in my real life job (new product coming out).

I did not concern about external vs internal clocking so much. I simply removed the clocking from the DAC board because the intention of the project is to keep it modular and flexible. So you can simply decide how to clock it by adding the right board for it. The dac pcb offers the option to select other formats then 24bit I2S or to set the dac as master or slave, it simply offers every configuration option you can find in the datasheet of the dac.

@Greogor: I'm in Bremen, where are you?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: living sounds on October 20, 2009, 06:58:36 AM
It's very important to have the clock as close as possible to the converter chips to reduce jitter. The modular setup gives the advantage to impliment a high quality clock, like this one:
http://tentlabs.com/Products/cdupgrade/xo2xo3/index.html


I'm in Cologne, so that's quite a journey. Maybe you could send over a prototype for a few days for testing?

Gregor

Hi,

sorry the project was delayed for some days now due to a lot of work in my real life job (new product coming out).

I did not concern about external vs internal clocking so much. I simply removed the clocking from the DAC board because the intention of the project is to keep it modular and flexible. So you can simply decide how to clock it by adding the right board for it. The dac pcb offers the option to select other formats then 24bit I2S or to set the dac as master or slave, it simply offers every configuration option you can find in the datasheet of the dac.

@Greogor: I'm in Bremen, where are you?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on October 20, 2009, 11:04:03 AM
An analog filter that works for 44,1 khz (= 20-22khz) should suffice IMO. The additional high frequency content at higher sample rates isn't imporant anyway.


Wow.  :o

Crippling higher sampling rates with subpar filtering, seems to me to defeat the purpose.

I don't want to get into a long debate on sampling rates, but I can't let this one go.

A short example

A crash cymbal has 40% of it's spectral content over 100kHz. Cymbals in particular sound like sushi(*) at lower sampling rates because of the limited bandwidth.

In my experience, many instruments just sound better at higher sampling rates, this is not subtle.  8)

Some background.

http://www.cco.caltech.edu/~boyk/spectra/spectra.htm

Quote
A summary of this paper's findings. Column one refers to the figure showing the spectrum in question. Column two identifies the instrument. Column three gives the sound pressure level measured at the microphone. Column four gives the measured frequency extension: For instruments with harmonics, this is the highest frequency where harmonics are still present; for those without harmonics, the highest frequency where the sound is still at least 10 dB above the background. (See text.) The last column tells what percentage of the total energy is contained in the range between 20 kHz and the limit given in the previous column.


Instruments With Harmonics

Fig.   Instrument                  SPL     Harmonics       Percentage
                                         (dB)     Visible To        of Power
                                                   What Freq.?    Above 20 kHz

1. Trumpet (Harmon mute)    96.      >50 kHz           0.5
2. Trumpet (Harmon mute)    76.      >80 "               2.
3. Trumpet (straight mute)    83.      >85 "               0.7
4. French horn (bell up)       113.      >90 "               0.03
5. French horn (mute)           99.      >65 "               0.05
6. French horn                    105.      >55 "               0.1
7. Violin (double-stop)           87.      >50 "               0.04
8. Violin (sul ponticello)          77.      >35 "               0.02
9. Oboe                                84.      >40 "               0.01

 
Instruments Without Harmonics

Fig.   Instrument           SPL   10 dB Above    Percentage
                                  (dB)   Bkgnd. to      of Power
                                           What Freq.?   Above 20 kHz

10. Speech Sibilant        72.     >40 kHz          1.7
11. Claves                   104.     >102 "            3.8
12. Rimshot                  73.     >90 "               6.
13. Crash Cymbal         108.    >102 "            40.
14. Triangle                   96.    >90 "                1.
15. Keys jangling            71.   >60 "              68.
16. Piano                     111.    >70 "               0.02



(*)Sushi as in sounds like ass. :)

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: living sounds on October 20, 2009, 05:23:06 PM
But does it sound better at higher sample rates because of the added content or because of the converter working better at these sample rates? I've heard converters that sounded better at higher and others that sounded better at lower sample rates. I think it has more to do with the digital filter. We cannot hear anything beyond 25 khz, so the additional content won't be important. It will not show up in the finished product anyway, unless you release your music to an analog format or a high end format like SACD. But the artifacts caused by the digital filter in the converter will definitely be audible by humans, and I find them more harmfull to the signal than any content beyond hearing range taken out by an analog filter . We could use a switchable filter though, a simple switch at the input/ouput would be a cheap solution.



Wow.  :o

Crippling higher sampling rates with subpar filtering, seems to me to defeat the purpose.

I don't want to get into a long debate on sampling rates, but I can't let this one go.

A short example

A crash cymbal has 40% of it's spectral content over 100kHz. Cymbals in particular sound like sushi(*) at lower sampling rates because of the limited bandwidth.

In my experience, many instruments just sound better at higher sampling rates, this is not subtle.  8)

Some background.

http://www.cco.caltech.edu/~boyk/spectra/spectra.htm

Quote
A summary of this paper's findings. Column one refers to the figure showing the spectrum in question. Column two identifies the instrument. Column three gives the sound pressure level measured at the microphone. Column four gives the measured frequency extension: For instruments with harmonics, this is the highest frequency where harmonics are still present; for those without harmonics, the highest frequency where the sound is still at least 10 dB above the background. (See text.) The last column tells what percentage of the total energy is contained in the range between 20 kHz and the limit given in the previous column.


Instruments With Harmonics

Fig.   Instrument                  SPL     Harmonics       Percentage
                                         (dB)     Visible To        of Power
                                                   What Freq.?    Above 20 kHz

1. Trumpet (Harmon mute)    96.      >50 kHz           0.5
2. Trumpet (Harmon mute)    76.      >80 "               2.
3. Trumpet (straight mute)    83.      >85 "               0.7
4. French horn (bell up)       113.      >90 "               0.03
5. French horn (mute)           99.      >65 "               0.05
6. French horn                    105.      >55 "               0.1
7. Violin (double-stop)           87.      >50 "               0.04
8. Violin (sul ponticello)          77.      >35 "               0.02
9. Oboe                                84.      >40 "               0.01

 
Instruments Without Harmonics

Fig.   Instrument           SPL   10 dB Above    Percentage
                                  (dB)   Bkgnd. to      of Power
                                           What Freq.?   Above 20 kHz

10. Speech Sibilant        72.     >40 kHz          1.7
11. Claves                   104.     >102 "            3.8
12. Rimshot                  73.     >90 "               6.
13. Crash Cymbal         108.    >102 "            40.
14. Triangle                   96.    >90 "                1.
15. Keys jangling            71.   >60 "              68.
16. Piano                     111.    >70 "               0.02



(*)Sushi as in sounds like ass. :)

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on October 20, 2009, 07:23:21 PM
But does it sound better at higher sample rates because of the added content or because of the converter working better at these sample rates? I've heard converters that sounded better at higher and others that sounded better at lower sample rates.

I'm basing my opinions on a lot of different boxes over the years, but currently I'm running an Apogee AD-16X
along with a Benchmark DAC-1.

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: living sounds on October 21, 2009, 04:04:35 AM
Have you tried downsampling audio that was recorded at a high sample rate using a high quality sample rate converter (the free Voxengo r8brain is the best one IMO)? I've found that a signal recorded at a higher sample rate with a converter that performs better at these higher sample rates retains this better quality even when downsampled (or subsequently upsampled again). This can only mean that the content above hearing range is not responsible for the quality difference between sample rates, but rather differences in the way the converter handles the signal at these rates, which again points to the filter.


I'm basing my opinions on a lot of different boxes over the years, but currently I'm running an Apogee AD-16X
along with a Benchmark DAC-1.

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 22, 2009, 05:01:37 PM
Hello,

besides the discussion about the sampling frequency (I do prefer higher frequencies, the 20kHz limitation is an invention of the CD recording industry we do recognize higher frequencies unknowingly as some studies with real music instruments demonstrate) I want to focus on the project itself again.
I've now a DAC board but with I2S it is not really useful. ;)
Here I found a ADAT receiver board:
http://electronics.dantimax.dk/Kits/Digital_audio/index.html
Does anybody know this boards? I think I've seen the pcb already somewhere here on the board. However I think it is quite useful. You can combine it with two of my 4channel boards and you have then already an 8 channel DAC with ADAT input.
Besides that for another application I need a multichannel AES receiver/transmitter. Therefore, I've decided to change my plans a little bit and to start with the design of such an interface this weekend.

Gregor, I'm planning to visit Cologne for a sightseeing/weekend trip. The date is not fixed yet, but I can let you know when I'm in Cologne and perhaps we can then do a test.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: freq_a_beat on October 23, 2009, 10:14:42 PM
I would definately be interested in something like that. I would like to incorporate something like that in a GSSL Clone ping
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on October 23, 2009, 11:41:44 PM
Great project so far.
I am pretty impressed from the pace of progression.
And for sure I am very interested in this project to fire up a DAC with 32 or even 64 channels 44,1 or 48khz for downmix.
(complete mixer dac)

What I am not that interested in is 96khz.
I want to explain why....
First, I am in one row with living sounds, there is no evidence people can percept 'more' at 96khz sample rate. Double blind tests show always that there is no perception of those 'high frequencies', not even 'sublime' or something like that.
All people who claimed to hear above 22khz that I met, could definitely NOT (try with a signal generator! Let someone outside the room switch it on and off...if someone can tell when it is on or off, tell him he is a lucky basterd, like I was iin the age of 20. My army doctor repeated the test three times because he didn't believe the results.)
Second, living sounds is also right about the converter chips sounding better at 96khz. I guess the lower sample rates simply suffer from poorer internal hardware downsampling.- I made tests with high quality software downsampling and yes, I found the results much better than directly recorded in 48 or 44.1. This is especially true for cheaper converters, but I noticed this even on the mytek AD (while it still has exceptionally good quality in 44.1 and 48).
Dan Lavry oftenly states that the optimal sample rate for audio would be 60hz theoretically, and I find 48khz sounds pretty good to my ears, beeing the nearest industry standard in the range.

OTOH, I really like 96khz when tracking because of the low latencies that are possible, takes alot of headaches out of live monitoring.
But mainly, I am interested in a downmix DAC box so latency is not a problem for me....

Another thing to remind is, that I did not find a free/diy SMUX solution that is known working so far.
The wavefront chip has been successfully implemented in a single speed dac project on this forum already - remember the optorec boards from Mikkel.
I guess double speed brings quite some new problems of it's own without really adding that much of value.

The great benefit that I seein this project is:
We should be able to find a complete affordable downmix dac solution for the lightbridge that might even beat the SSL alpha link (at least in channel count....).
Personally I would even go for 64ch of single speed because I still have a (synced) 4 card sonorus daw that is capable of that (and I do not like the idea of mixed brand dac's due to different latecy issues or 8x Behringer ;D).

As for SMD soldering:
Don't be afraid of this.
It is actually very easy, in fact easier and faster than thru-hole. Even with the dac chip.
Raphael already explained the way to go. If you do not believe that it is no problem, take a piece of modern electronics from the junk pile and practice a bit of soldering and desoldering. You will be surprised how easy it is.
I do quite some work on computer mainboards and after some hours of practice you might be able to solder and desolder components that you can barely see without magnifiying glass. You should buy yourself a high quality pair of fine tweezers, though. Money well spent anyway.

Kind regards and many thanks Raphael,

Martin


P.S.:
Voxengo r8brain free is really great for downsampling, I totally agree. High quality does not need a Saracon always...


Title: Re: Modular multi channel DIY AD/DA Box
Post by: living sounds on October 24, 2009, 05:27:20 AM
Voxengo r8brain free is really great for downsampling, I totally agree. High quality does not need a Saracon always...


It's the best. There is a very usefull comparison here: http://src.infinitewave.ca

The thing is that most of the downsampling algorithms with good frequency and phase response seriously compromise impulse response. To my ears that's even worse than alising, as the sound loses definition. More or less the same happens with the digital filters in the converter chips. With R8brain free you loose a little at the top of the spectrum (the dog/bat area :-)), but the signal stays untouched everywhere else. The current version doesn't suffer from the phase flip anymore. It's better than the pro version and better than Weiss and all the other expensive ones in the test.

In a nutshell a converter chip where the filtering could be turned off completely and be substituted with an analog one would really yield far better dynamics (= impulse response). From a sonic perspective that's far more important than phase or frequency response IMHO.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ask on October 24, 2009, 06:04:32 AM
For the sake of clarity and usability, could we try and stick more to the project in this thread, and take the filter and sample rate discussions to the drawing board area?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: playboss on October 24, 2009, 06:38:37 AM
Quote
With R8brain free you loose a little at the top of the spectrum (the dog/bat area :-)), but the signal stays untouched everywhere else. The current version doesn't suffer from the phase flip anymore.

 :o :o :o

going to test it.

1. your description not co-incides with math btw. That little r8brain ringing is misleading, because the ringing itself lies at lower frequency than the "long" ringing of other filters. One lies at 18khz, the others at >21khz.  

2. theres no phase shifting in r8brain free. Its linear phase. As such should be avoided because the pre ringing it embeds(!) is at lower freq's.  

3. so you hear the ringing in the dog / bat area, wow ... Too bad sampling theorem is something different.

Quote
It's better than the pro version and better than Weiss and all the other expensive ones in the test.
ha-ha-ha-ha ! My math is better than your matchbox.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: living sounds on October 24, 2009, 11:57:44 AM

1. your description not co-incides with math btw. That little r8brain ringing is misleading, because the ringing itself lies at lower frequency than the "long" ringing of other filters. One lies at 18khz, the others at >21khz.  

2. theres no phase shifting in r8brain free. Its linear phase. As such should be avoided because the pre ringing it embeds(!) is at lower freq's.  

3. so you hear the ringing in the dog / bat area, wow ... Too bad sampling theorem is something different.

Quote
It's better than the pro version and better than Weiss and all the other expensive ones in the test.
ha-ha-ha-ha ! My math is better than your matchbox.

1. Judging only from the impulse response pictures the ringing is considerably lower with R8brain free, it looks like the same frequency to me, too. But if you've done the measurements it might be at 18khz, but still of considerably lower amplitude.

2. There was a 180° phase shift in the version used in the test, as can be witnessed by the impulse response being "upside down" in the graph.

3. I never claimed I could hear anything in the dog/bat area. Obviously didn't realize the ringing was that high (if this is true). It might still get into the audible spectrum, via intermodulation distortion, for instance.

BTW, I wouldn't know much about the math, I go by observance and listening tests.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: stitch-o on October 24, 2009, 12:07:42 PM
Total side-note:
What about a serious analog path to the DAC chips? Transformer balanced I/O?
With a bit of tweaking, this box might be able to go from AD16x land to Burl or JCF maybe?
I saw one of these JCF DACs at AES and it looks really cool!
(http://img257.imageshack.us/img257/4863/jcfdac.jpg)

On any other subject here, I am a noob and leave serious discussion to the experts....
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on October 27, 2009, 10:06:59 AM
OMG. I think I would never go for tubes in the DAC. Serious analog filtering? Sure. But please no tube effect sound.
I would stay clean, affordable and silicon for sure. Leaving 'sound' to the summing stages after the DAC. Much more versatile.

Raphael,
the dantimax.dk boards have been designed by Mikkel for a forum project to feed Apogee cinema DAC's that have been grabbed in a sale.
Very good off-the-shelf diy solution. No need for reinvention of the wheel.
But I guess if we go for higher channel count, design should/might be different because of proper clock distribution to all chips - am I right??
And so YES, I find the I2S DAC boards,*very* useful and versatile!
There are all options for feeding them like one would want to.
Consider 8ch Adat and 4ch AES/EBU or spdif with one clock in one case, all same sound!
Somewhere in future, one may even have an opensource/openhardware madi interface.
Or consider usb audio feed from some of the TI newer chips.

Other point, does anyone have a promising idea for proper s/mux (if 96khz is so desireable by many of us)?
When I researched the wavefront chips some years ago, I did not came up with a conclusion how to do it right. At least, not without some serious microprocessor programming.

An AES/EBU board might be a much simpler design than Mikkels ADAT boards.

I am very, very curious how the test boards compare at the upcoming listening tests with pro grade dac's that you planned.
If they can hold up to, say, benchmark or swissonic or something in that range, I would be in for the next batch of boards definitely.

Thanks alot for coming up with this.
Kind regards,
Martin 

Title: Re: Modular multi channel DIY AD/DA Box
Post by: mitsos on October 27, 2009, 11:09:17 AM
Sorry to butt in at this stage, I think this project is uber-cool. Congrats on getting it this far! Hope to be able to put one of these together at some point!

I have one question about the technical side of AD/DA. I was reading a recent Lab thread comparing analog summing to ITB mix, someone suggested that ADAT was inferior to AES/EBU.  Most people (except for that one person who felt pretty strong in his opinion) said that it's all 0's and 1's and that there is no difference, and I am wondering what you all think (those of you who understand the underlying technology, not like me who just plug the digi stuff in and hope it works), especially rafael since he is (maybe) choosing to go down the ADAT road.  Is there any technical difference between these (or any) digital protocol, or is it all the same once it gets to digital?  I mean SSL makes all those format converters, so I always I assumed it was pretty much the same.

sorry if this is OT...

Title: Re: Modular multi channel DIY AD/DA Box
Post by: living sounds on October 27, 2009, 11:28:07 AM
Sorry to butt in at this stage, I think this project is uber-cool. Congrats on getting it this far! Hope to be able to put one of these together at some point!

I have one question about the technical side of AD/DA. I was reading a recent Lab thread comparing analog summing to ITB mix, someone suggested that ADAT was inferior to AES/EBU.  Most people (except for that one person who felt pretty strong in his opinion) said that it's all 0's and 1's and that there is no difference, and I am wondering what you all think (those of you who understand the underlying technology, not like me who just plug the digi stuff in and hope it works), especially rafael since he is (maybe) choosing to go down the ADAT road.  Is there any technical difference between these (or any) digital protocol, or is it all the same once it gets to digital?  I mean SSL makes all those format converters, so I always I assumed it was pretty much the same.

sorry if this is OT...




AES/EBU has advantages over ADAT in terms of jitter. This wouldn't be a problem however, if you clock the converter internally, which is the best solution as long as there is a clock of reasonable quality inside.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on October 27, 2009, 11:39:54 AM
AES/EBU has advantages over ADAT in terms of jitter. This wouldn't be a problem however, if you clock the converter internally, which is the best solution as long as there is a clock of reasonable quality inside.

+1.

ADAT is fine for moving bits from one place to another, as is AES/EBU. Neither should be used as converter clock source if you can help it at all, with the standard Wavefront ADAT receiver being somewhat worse than most integrated SPDIF/AES receivers.

For a given amount of money/design effort a good free-running crystal oscillator will always beat a slaved clock jitter-wise. If for some reason you must slave your converter to an external clock, use either WC or AES11.

JDB.
[whether WC or AES11 offers better jitter performance depends on the application. On paper a competent AES11 implementation will beat a competent WC-based PLL, but getting AES11 right is harder]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mitsos on October 27, 2009, 12:35:50 PM
Cool, thanks for the replies guys. I assume then this will be internally clocked? 

I'll go read the rest of the thread now.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on October 27, 2009, 12:49:45 PM
For this to work in my setup and to provide much need flexibility, I would like the ability to have the option of an external WC source clocking the converter. Unfortunately, without WC this converter will be pretty much useless since I'm clocking my entire studio with an external WC source. I would also like the ability to run @ 96Khz via SMUX.

I totally understand if it's too ambitious for this project, but without this it will severely cripple my ability to integrate it into my current setup.

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: spreemusik on October 27, 2009, 12:59:27 PM
WC Input is definitely necessary on ANY digital audio equipment.
I'm also watching this thread with great interest, would love to build 32 Channels of AD/DA in good quality, maybe even more.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on October 27, 2009, 10:35:44 PM
Hehe, I somehow knew this kind of discussion would come up.
Surely, internal clocking wins hands down against WC, IF the clock is done just properly (not even stellar).
And I understand most of you would implement WC. If I remember it right, mikkels boads even have the option for an external WC (at least, WC can be easily added).
But for my side, I would be very glad to build a solution that can internally clock alot of channels leaving external clocking only as an option. In this case, the less external clcking, the better. One 32 channel DAC with one internal clock. This is something I would be after.
(I *guess* that clocking 64 channel would bring some more problems laying out clock signals to the chips. Maybe I am wrong.)
Mainly because this would eliminate the need of WC busses between 8 channel boxes.
I guess this makes boxes like DA16(x) and the SSL alpha link so attractive as well to many people. Less possible clocking/jitter probs, less external cabling etc also means less service and more production.
At the moment, 24channel was the biggest on the market I am aware of. (I do not know if the SSL has more than one clock internally...anyone? Maybe clock routing length is a problem at above 16/24 channels I/O?)
Maybe it is even fine to just spread one clock to all Mikkel optorec boards to get a fairly good result. Well, surely not...

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mainmachine on November 02, 2009, 01:58:58 PM
Anyone have any thoughts on interfacing these DACs with a PC via firewire? I've done a little research, but I know very little about digital communications. Would a FPGA be necessary? a DSP chip?

Here's an interesting firewire/ FPGA card that might be applicable:

http://www.orsys.de/322c6713.htm

The idea is that it would communicate via firewire between a pc DAW and the DAC unit.

It seems like SPI would be more useful than I2S for multi channel use, although if you're going from AES to the DAC, I2S might be better suited.

Anybody else looking into this, or are the majority of people interested in ADAT lightpipe interface?

I can't see using ADAT for more than eight channels- the number of cables/ ports you'd need to do high channel counts would be annoying and/or expensive.

-Dave
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on November 02, 2009, 02:30:37 PM
Anyone have any thoughts on interfacing these DACs with a PC via firewire?

Nothing that an EE with the relevant experience can't do in a man-month or two. The problem is finding one who will do it for little or no money. As much as I love IEEE1394 it's rather non-trivial, and I don't believe that enough applicable open cores are available to make this a simple matter of plug-and-play.

Here's an interesting firewire/ FPGA card that might be applicable:

http://www.orsys.de/322c6713.htm

That has only the transceivers (ie: the easy bits, which are simple enough to bolt onto any FPGA).

The idea is that it would communicate via firewire between a pc DAW and the DAC unit.

It seems like SPI would be more useful than I2S for multi channel use

...why? Apart from the fact that most ADC/DACs don't speak SPI you get more signal edges, more transitions, more noise.

Anybody else looking into this, or are the majority of people interested in ADAT lightpipe interface?

I am pretty partial to MADI myself, but MADI PC interfaces are rare and expensive. MADI would be much simpler to implement in an FPGA.

I've considered streaming low-latency audio over a (possibly dedicated) Ethernet link. The hardware is doable, of a same level of complexity as MADI, with equal or better performance. The hard bit here is that someone would need to write an ASIO (or similar) driver for it. Under Linux that would be doable, but if you want Windows compatibility (which one? XP? Vista? 7?) it gets pretty hairy pretty fast.

At the end of the day you need to get the data into/out of a DAW, and that tends to limit your options.

JDB.
[ADAT's a bit like McDonalds: nobody over the age of ten is a huge fan but you can get it everywhere]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mainmachine on November 02, 2009, 03:06:38 PM
JDB: Thanks for the input!

My lack of digital experience shows in regards to SPI vs. I2S. I was thinking it'd be better from a cabling standpoint.

So how can I get my PC to send audio data from my DAW software to the DAC via I2S with minimal cabling?

It would be great if I could use an available PCI card with simpler cabling than multiple ADATs, like TDIF or AES.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: skipwave on November 02, 2009, 03:38:10 PM
[ADAT's a bit like McDonalds: nobody over the age of ten is a huge fan but you can get it everywhere]
:D :D :D

Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on November 02, 2009, 03:40:30 PM
It would be great if I could use an available PCI card with simpler cabling than multiple ADATs, like TDIF or AES.

Can't get much simpler than that. TDIF is already very close to I2S, but I'm not sure if anyone still makes/sells (new) TDIF cards. Alas, cards with loads of AES links aren't exactly common or cheap either; for equivalent I/O capacity ADAT would still appear to be cheapest.

For 'one cable' it is hard to beat MADI.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mainmachine on November 02, 2009, 04:51:32 PM
MADI looks great!

The least expensive TDIF solution I could find is the Sydec Mixtreme 192. Two TDIF connectors for 16 channels I/O @48kHz, 8 @ 96kHz for $595 USD direct from Sydec. Not a cost-friendly solution at all.

-Dave
Title: Re: Modular multi channel DIY AD/DA Box
Post by: nielsk on November 02, 2009, 04:59:10 PM
RME makes lots of MADI hardware that is excellent, I have some PCI cards I bought for $500 used... not rare or hard to come by. It is very easy to get MADI into the computer AND you can run it over fiber for up to 3 Kilometers. My entire live recording rig runs on MADI, I would LOVE to have a way to build a large analog to MADI converter, say 64 channels (what one MADI stream holds....)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on November 02, 2009, 05:13:49 PM
If the question is audio over ethernet, AES51 seems to fit the bill. IIRC it will function over ordinary switching hardware as it's a layer2 protocol and uses normal MAC addresses. There are even some provisions to pass through IP traffic so that you can have it on a casual network. Anyway, if an ASIO AES51 driver would be required, I think I could conjure that up, I've had experience with linux and windows MM device drivers, so this could be explored if there is sufficient interest.

Lacking that, I'd endorse MADI. Sure, the cards aren't cheap but the protocol is nice and the cables can be long.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on November 02, 2009, 06:49:31 PM
If the question is audio over ethernet, AES51 seems to fit the bill.

Hadn't seen that one before. It looks... messy, but not too hard to put into an FPGA. Not when compared to 1394 or USB, at any rate.

Anyway, if an ASIO AES51 driver would be required, I think I could conjure that up, I've had experience with linux and windows MM device drivers, so this could be explored if there is sufficient interest.

I expect that would be very useful.

Lacking that, I'd endorse MADI. Sure, the cards aren't cheap but the protocol is nice and the cables can be long.

Yes. From a design POV I would prefer MADI, but anything that can properly run over commodity hardware such as Ethernet would have the advantage.

I'm considering a FPGA-based I2S-to-whatever board, but don't hold your breath as my to-do list is longish these days.

(mini-rant: Googled AES51 for a bit. So it appears that the AES decided to do their own implementation of ATM-over-Ethernet. Why? What was wrong with the dozen or so existing ATM-E encapsulation methods which have been developed in the past fifteen years? There's very little you can do on the IEEE802-level to make any new ATM encapsulation scheme more audio-friendly. So why not use what's already there? Would that make the committee members' products and solutions not stand out enough as Pro Audio Rated? Is it NIH? Granted, I'm rather opinionated even before reading the full standard, but experience shows that in these cases it's generally warranted if my prejudices are extreme.)

JDB.
[sure, there's nothing new here. If you look hard at MADI you'll see a bunch of FDDI-engineers shouting Here! Take our standard! It never managed to get any market acceptance, but it's technically sound! You folks do sound, right?]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on November 03, 2009, 04:21:42 AM
I think your rant is spot on. We didn't need AES to invent this, but that's how it is. We can choose to ignore it and make our own if it proves too messy. In any event, I'll have some thorough look over the protocol and the ASIO lib and see what it would take to implement such a beast.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 04, 2009, 04:39:27 PM
Wow, MADI, Audio-over-Ethernet, Firewire... if someone is willing to develop such a board I'll definitly support that.
I know that there are several OpenSource implementations of this protocols on FPGAs. What keeps me away from doing such a design is that I do not own the stuff for programming a FPGA.

Just one note about the current project status: I started to design the AES receiver/transmitter boards. Unfortunately, I had to redesign the receiver board. The problem was that a least one receiver must run as slave so that the I2S port is clocked from the master. That is needed because the PCM4104 has two data inputs but only one lrck and bck input. The DAC expects the two data inputs to be synchron. Of course that cannot be guaranteed if the receivers are sourced with AES signals form different sources and let them recover the clock signals from the incoming data stream.
So I changed to the Cirrus CS8416 receiver chip and they are always used as a master/slave pair  to source one PCM4104.
I'm now thinking if I want to keep master/slave pair design for all receiver when expanded to 24 channels (which would mean that I have 6 chips configured as master and 6 chips as slave) or if only one chip is the master and the other 11 chips are slaves.
To avoid confusion: I'm only talking about the configuration of the I2S port if the DAC I2S port is not the master. Of course it is possible to configure the DACs as master and let them clock the receivers. Besides that all the chips can be run from one system main clock.

Raphael  
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuc224 on November 05, 2009, 04:20:58 AM
Hi raphael, quick off topic question. Are u planning on designing a 2 channel high end ad or da? Thanks and sorry for the off topic question.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 05, 2009, 05:03:54 AM
Well, not now. I first want to finish a multi-channel box because that is the main target. Of course it is a nice idea to have at least 2 or 4 channels with highest quality based on a PCM179x or something like that. But that would be definitly to expensive for a multi-channel box with >24 channels.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 05, 2009, 09:57:46 PM
Hi guys,
in the meantime I researched a little bit more in the way of diy-able interface technology.
Right now I found two interesting options that are more or less functional building blocks.

Firewire IEEE1394:  I took a look into DICE II chips from TC electronics. In the meantime it is possible to get them in single quantities e.g. at profusionplc.com.
As I understood it, they are (co-)designed by D.F.M, german digital audio specialists. They are already used in several musical devices and are widely configurable, contain a programmable dsp section etc etc.
They are even kind of affordable in small quantities.
However, it looks like the most complete building block available for that kind of task.
Implementation might still be far away from trivial. (even the package size is anything but diy-friendly)

ADAT receiver:
Interestingly, I found a completly open source FPGA core written in VHDL that claims to be tested working (status stable/fpga proven). Might be the lowest latency way possible (?) and might even be improved with integrated s/mux IF someone is capable of designing and testing VHDL in the field of DSP/audio.
http://opencores.com/project,adat_optical_feed_forward_receiver (http://opencores.com/project,adat_optical_feed_forward_receiver)
I must confess personally I have no experience with FPGAs at all aside from some rough theoretical knowledge.

On the opencores site, there is even a MADI core available, however it is still in beta stage, means in simulation and not tested in an fpga. So maybe something to bookmark for future updates.

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: syn on November 06, 2009, 03:44:16 AM
Hi rkn80,
              once again thank you for doing this.I was wondering what is the status of the ADAT board?Are you
going to make it?

Best
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 07, 2009, 05:23:11 AM
syn,

I decided to delay the ADAT board for a moment because there's is already a diy receiver board for it that can be used together with the DAC. So I think it is better to design an AES input first. I'll go on with ADAT when the ADC is coming alive, starting then with an ADAT transmitter board.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: syn on November 07, 2009, 02:56:22 PM
Thank you, Raphael.
             
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Freddy G on November 11, 2009, 02:15:05 PM
I'm watching this thread with great interest....good work Rapheal!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on November 11, 2009, 03:40:01 PM
Wow, MADI, Audio-over-Ethernet, Firewire... if someone is willing to develop such a board I'll definitly support that.
I know that there are several OpenSource implementations of this protocols on FPGAs. What keeps me away from doing such a design is that I do not own the stuff for programming a FPGA.

How about USB then? New MacBooks don't come with FireWire support anymore (http://www.apple.com/macbook/specs.html (http://www.apple.com/macbook/specs.html)).

This EtherSound stuff looks interesting: http://www.digigram.com/products/product_infos.php?prod_key=11100 (http://www.digigram.com/products/product_infos.php?prod_key=11100)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on November 11, 2009, 06:44:52 PM
It's cool in that they probably have an ASIO driver for their Ethernet/audio protocol, but the spec seems to only be available for (paying) licensees as is the FPGA code... If someone can do at least the FPGA hardware part, I'd be interested as stated in creating an AES51 ASIO driver, possibly even a CoreAudio driver. The FPGA software part would be tricky, but I could try my hand at that as well, though, it is hard without the related hardware to develop with.

For those who haven't followed through with the thread, this would mean that you could stream up to about 32 channels of audio at 96k through an inexpensive Ethernet cable that you probably use to connect to the internet; what's more, you could probably just plug the A/D D/A into your router and browse the net/email over the same cable.

For me, this would be a nice solution because I could have a remote recording rack loaded with a racked PC and converter box. After a session I could bring it home for mixing and use a simple Ethernet cable to connect both the PC and converter to my home network, where I could use that same cable to stream files off of my racked recording PC to the mixing PC and use the converters in my converter box for listening or using outboard gear, thus not needing another converter box for mixing purposes but rather reusing the one used for recording. The additional benefit of not needing to buy ADAT or MADI interface cards is there as well..
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 11, 2009, 09:10:04 PM
OK, some info on the USB interface option.
There are some nice newer USB-all-in-one adda comverter chips with spdif and direct da chip interfacing available from TI. They need minimal external components but unfortunately, they are all restricted to 16 bit (damn!)....
The dedicated usb audio receivers are a bit more delicate to implement.
ATM, usb is not a favourite for pro-audio at all. Ironically. in the meantime USB runs really stable under all known OSes....
Please be notified that almost all serious manufacturers dropped serious usb development  on pro-audio because they did not see any future for 2ch I/O. (And usb issues in the past did no good for their reputation).
(Most manufacturers i heard of refused to develop for more channels due to stability reasons, despite usb 2.0 availability)
So maybe no field for diy really...
I found ONE interface that claims to interface with ADAT from USB, but did not check it in reality yet...product is EOL, it's a B.ringer.
I guess one should get a ready-made usb card and interface to the converter via an AES/EBU or S/PDIF board.

For the ADAT option:
All I heard about the Wavefront chips is, that they spec really not that good (jitter issues etc), OTOH, they are readily available (but kind of expensive).
If one could live with that, Mikkels board is the way to go.

To be more on top of the field, an FPGA could be the solution really. extremely low latencies, and functionality could be modified/updated 'in hardware'.

I'm still investigating about the DICE chips, and think I read they can be used 'offline' (without IEEE1394 connection) like a format converter (like AES/EBU to i2s, ADAT 2 I2s, Adat to I8s and the like).
Could be a nice option for a ready-made, affordable and tested very functional fpga. needs a flash mem and sdram for the minimal system. The flash needs a minimal application to configure the functionality.

The open core adat receiver is still an option, but for myself I am a bit hesitating to get more into the field of designing and burning fpgas...but if all other options have drawbacks, why not?

Best regards,
Martin

PS: I am very interestedly lurking at the AES51 / ATMoE discussion now. I wish I had beed into fpga before...this stuff is very interesting and opens up quite a new dimension (IMHO any working solution of this kind would be mostly welcome, so I think it is not necessary to stuck to AES51 of MADI compatibility).
BTW, I would not let my router be involved into 64 channel audio streaming, hehe, but just a direct ethernet cable connection, what a great option it would be!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on November 12, 2009, 02:53:03 AM
The nice thing about a FPGA solution is definitely the freedom to choose your protocol (we wouldn't be limited to MADI, ADAT or AES51). Though, in reality, you still need a chip like Marvell 88E1116R to interface with Ethernet for example. Even if people wouldn't like to use routers, an additional gigabit ethernet card is way cheaper and more readily available than a dedicated MADI/ADAT card..
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on November 12, 2009, 03:32:45 AM
Yes and even 10 Gigabit interfaces are coming allowing even larger systems. Gosh I wish I had some experience in this field of programming, I would gladly help you baadc0de ;) How about harnesing Open source community to help with FPGA? This project will be huge hit and benefit everyone 8)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 12, 2009, 04:21:55 AM
baadc0de,
you are definitely right. One might need a physical layer ethernet chip in the converters interface. But the interfacing on PC (or MAC) side is, where it gets interesting really, esp. from the financial POV...
It didn't let me sleep, I wanted to know how hard it would be to do a driver for, say Win XP...(hardest one first...)

Actually I investigated and came up with the following on my machine:

- I found a simple open source raw packet driver for xp. It has to be installed as a protocol for the physical ethernet port and accepts a (predefined) number of bytes raw data.
I installed it thru the network devices property page and disabled all other protocols.
After a reboot, I launched a test app that was able to identify the device that the protocol was applied to and sent some twenty bytes of raw data directly to the ethernet. Voila, it was way more easy as I ever expected to bypass all those nasty network layers, cool!
I found a similar driver for linux, even more easy I guess. Did not test it...

-Now, that I grew more confident, that the computer side is doable without aeons of development time, I got heroic and installed the latest WINDDK.
(I had no good feelings from my last try in developing a driver, has been a while ago...)
Starting the development environment I found they have a new virtual audio sample driver - WDM with full support for waveformatextensible !!
(Was a big issue in development once, noone ever shared sources on this kind of drivers really....remember the difficulties to obtain drivers from several companies for NT and upward some yesars ago?)
Exactly what is needed for developing a multi channel driver with more than 16 bit!
I instandly built that thing (yes it worked flawlessly from command line and compiled with just 2 warnings...) and got a driver file (sys).
I installed that one with the 'New Hardware Wizard', because it has no hardware relation. Guess what, an example .inf was included by MS and exactly worked like it should. Great.
Fired up my Sonar DAW: The WDM driver was tested working with the specs defined in the driver as an 8-channel device. OK, it actually does nothing right now, but it was flawlessly loaded, identified and exposed itself exactly like any other multichannel card driver would do.
Wow, much more than I expected from a few hours of investigation...

TODO's:
-expanding the virtual audio driver with I/O functions to communicate to the raw data NDIS driver.
-Decide on a lightweight audio data protocol and implement.
-setup another machine with the same drivers.
-Test 2 daws communicating to each other and measure roundtrip latency! BTW this would be a cool application even with no converters involved - each daw would see the other one as a soundcard thru their ethernet cards.
I really hope it works in the region of 'realtime'...
After tests with WDM/KS, I will try to test the same with Asio4All, so everyone will take a look at this point latest ;D.

Well, now I am more than surprised that the seemingly hard parts (bypassing network layers/functional multi channel wdm audio driver skeleton) actually are no rocket science anymore....like it seemed to be some years ago.

I hope someone will try his digital hardware skills on the converter side of things (something I am not nearly that deep into)....

Kind regards and feel free to drive this project further,
Martin

  
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on November 12, 2009, 05:37:45 AM
Wow, good finds Martin.

A few additional points to ponder on, if I may..
- people will be configuring these A/D D/A boxes in a plethora of configurations (12 out, 36 in... whatever) so there must be means to configure the driver, either through querying the other side over ethernet or a settings panel of some sort. Also there would need to be a mechanism for setting the default sample rate
- we can send/receive raw packet data through the good ol' WinPcap: (http://www.winpcap.org/)
- I would urge, however, that the audio protocol still use ethernet as the phy layer... this would be useful because you can use ethernet switches, repeaters, cable extenders, physical layer converters etc. that are on the market already to ease installation in the millions of configurations people would probably like to use this with

Some ideas:
- i'd create a sourceforge project (as a name, openaoedrv is available..) so that the code is available to everyone
- first idea is probably indeed to create a loopback/remote driver where two DAWs could exchange audio through a lightweight audio over ethernet protocol (what a mouthful!). This is a good idea because then the driver is tested thoroughly on the PC side and can aid HW debugging
- OC FPGA community might be interested in creating a FPGA core that would be compatible with this driver or at least helping with that, does anyone know how to make them interested?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: spreemusik on November 12, 2009, 09:18:08 AM
Please don't make this too Windows-centric.
Oh, under Linux (and Mac, I think) there's Netjack, which allows audio streaming over Ethernet. Open Source, of course, so maybe someone proficient could have a look at their network code.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on November 12, 2009, 11:51:11 AM
As far as I have seen Netjack is IP-based, thus it would be much harder to write FPGA code for it. As for supporting other OSs, the driver would be open source and someone proficient should have none too much problems converting it to Linux. As for CoreAudio and mac, i'm sure if nobody else, I'd be delighted to port it, but not before it works on windows.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 12, 2009, 03:42:53 PM
Well, I said 'hardest first' when talking about windows wdm drivers...
I do not know enough about linux and mac driver architecture, really.

At this point, it is all at a very early stage - when the driver evolves (and my practice in driver programming, too), I hope it could be useful even without an additional converter stage, as am ethernet inter-pc soundcard. So I just started work without any confirmation someone would do an fpga design...
Right now, I am not sure about possible licensing issues with wdk and publishing the source - but it's not worth it anyway at this early stage. Nevertheless I will publish the source at a later point, when the driver is more than a skeleton.
I already figured out, how to set max number of channels and bit depth to show to the system. Nevertheless, the 'real' functionality is still missing and I have to dig much deeper now.

I am aware of my posts beeing maybe alot tooo MS related for the Mac people out there, I am sorry for that.
I would really be interested if a  Mac solution for raw data transfer over ethernet is possible as well...

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on November 13, 2009, 02:14:24 AM
If a driver would use WinPCap for Ethernet information exchange, it would be much simpler to port to Mac and Linux because libpcap (UNIX equivalent lib) is available on those platforms.

I would suggest that the Ethernet communication part be abstracted away (and use *PCap) so that specific OS interfacing may be done separately for any of the OSs concerned. More or less there will be provisions in all of the OSs to: attach/detach client, query/set configuration, read/write data and possibly some sync commands.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Moby on November 13, 2009, 08:29:52 AM
Quote
I would really be interested if a  Mac solution for raw data transfer over ethernet is possible as well...
Me too, please think about Mac users  ;D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 16, 2009, 11:21:55 AM
Someone with experience in programming for osx out there, possibly?

Winpcap looks nice on paper, never worked with, will study...
Win-style driver models are really complicated, will try to document the relevant portions of code with portable functionality. Grr, i liked c-style programming so much more than c++, *sigh*. (Coming from pascal/delphi.)
Hope to get something usable worked out.

Thanks for the input.
Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Moby on November 16, 2009, 02:21:58 PM
Quote
Someone with experience in programming for osx out there, possibly?
Hmm, maybe I know someone...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 18, 2009, 06:17:33 PM
Hello everybody,

before talking about the driver you should think about the hardware. Who is willing to make a fpga program etc. Writing a driver is IMHO not so difficult at least not on *nix systems like Mac and Linux. Windows? Who is using that? We should talk about real operating systems not about toys...  ;D
However think about the hardware first.

Coming back to phase one of this project: The design of the AES receiver/transmitter is almost finished. I'm doing the last little tasks on it: Some voltage regulators and some pin headers have to be added. I hope I can finish that over the weekend because the next days I have to be away on business.
But some words already on the design:
There wil be only one board for all AES interface configuration. The same board can be used as a receiver or a transmitter or both full-duplex. You can either use it as a two mono channel receiver or two mono channel transmitter in the smallest configuration up to 12 mono channels in and 12 mono channels out. It depends what you put on the board and you can always upgrade later by stuffing the next group of parts. The size of the board is the standard euro pcb size (160mm x 100mm).
More details will follow later.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 18, 2009, 06:58:11 PM
Nice to hear you make so good progress on the AES board!
So there are AES and ADAT (dantimax) solutions available soon - enough for lots of people to get started, I guess!
Thanks for all effort you put into this.

Quote
Windows? Who is using that?
Ah, well, me and a few people I know. I quit using Mac at 8.5...
Well, we are freaks and just a small community of commandline hackers, but may grow soon and sometime in future we...eh... oops, STOP, I mixed up Win and Linux....
 :P :) ;)

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on November 18, 2009, 11:09:13 PM
I understand AES is superior in offering higher sample rates than ADAT, but how are we supposed to get AES into our computers? The only AES cards I've seen cost a fortune. Any cheap methods for many (ie. 24-36) channels? If not, what's the point, besides for the sake of it?

Ideally I think firewire connectivity would be best but then someone has to write and support drivers and seeing the trouble actual companies have doing this with stability I'd be nervous.

If not that, at least there exist cheap, large channel count ADAT > firewire converter boxes that will work well. But for that we need ADAT outs.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Moby on November 19, 2009, 07:34:46 AM
Quote
I would really be interested if a  Mac solution for raw data transfer over ethernet is possible as well...
Me too, please think about Mac users  ;D
Well,my idea wasn't so bad but it seems that developing such a driver isn't a piece of cake. I'm afraid that there is no much guys ready to do that , especially withouth "additional motivation" ;)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: 0dbfs on November 19, 2009, 08:28:55 AM
I understand AES is superior in offering higher sample rates than ADAT, but how are we supposed to get AES into our computers? The only AES cards I've seen cost a fortune. Any cheap methods for many (ie. 24-36) channels? If not, what's the point, besides for the sake of it?


The Lynx AES16's provide 16 channels of AES I/O in a single PCI card for $600-$700. You get 24 channels of MOTU ADAT I/O for just under $1k. RME's HDSP(e) provides 24 channels of ADAT I/O for about $700...
The thing I like about the MOTU is that you can add additional I/O boxes to the 424 card to provide up to 72 channels of I/O and the CueMix software is very flexible for routing and preparing cue mix's.
And if you would be integrating this with a PTHD system, you have the option of either AES or ADAT with the digital 192's.

I am personally interested in both ADAT and AES options.

Cheers,
j
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on November 19, 2009, 09:26:31 AM
Reminder:
Ethernet based solution: use your existing network card = 0€ for what 72 I/O (with gigabit card that has been standard for years)... Of course ASIO drivers aren't available yet and lacks routing software (unless someone does one). Obviously the best choice over what ever commercial interfaces ;) Ethernet standards keep getting faster, firewire is propably going to be burried when USB 3 comes...

My point: Anyone who can help baadc0de and smallbutfine please chime in ;)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on November 19, 2009, 09:30:48 AM
Reminder:
Ethernet based solution: use your existing network card = 0€ for what 72 I/O (with gigabit card that has been standard for years)... Of course ASIO drivers aren't available yet and lacks routing software (unless someone does one).

Exactly,

Ability to utilize an additional, significantly different interface to my existing RME ADAT ASIO Interface, Apogee AD16-X, Benchmark DAC-1 system in my DAW = ZERO (0).   :'(

Ability to seamlessly add another ADAT I/O converter into my existing setup = EASY.  8)

I suspect many are in the same position.

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on November 19, 2009, 09:36:02 AM
Reminder:
Ethernet based solution: use your existing network card = 0€ for what 72 I/O (with gigabit card that has been standard for years)... Of course ASIO drivers aren't available yet and lacks routing software (unless someone does one).

Exactly,

Ability to utilize an additional (and significantly different) interface to my existing RME ADAT ASIO Interface, Apogee AD16-X, Benchmark DAC-1 system in my DAW = ZERO (0).

Mark

Oh well, obviously, But you could sell your stuff and spend it building rkn80 AD/DA :D Enough, ADAT/AES is readily available, ethernet stuff in far future. Nevertheless I'm excited 8)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on November 19, 2009, 11:14:36 AM
Reminder:
Ethernet based solution: use your existing network card = 0€ for what 72 I/O (with gigabit card that has been standard for years)... Of course ASIO drivers aren't available yet and lacks routing software (unless someone does one). Obviously the best choice over what ever commercial interfaces ;) Ethernet standards keep getting faster, firewire is propably going to be burried when USB 3 comes...

My point: Anyone who can help baadc0de and smallbutfine please chime in ;)

Ethernet sounds awesome if it can be done.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 20, 2009, 09:38:42 PM
Hi guys,
finally some more interest in the interface discussion, nice!
For all people interested into adat, as said before there already is a solution available with Mikkels board.
So there is no obstacle for you if you want to keep your system like it is and add the hardware.
Up to 48khz. Awsome enough one could immediately start building without any fear there would be no interface available ;-) .

Next, AES definitely has it's advantage of the low jitter level that can be achieved.
Obviously preferable for tracking or mastering (low channel count, high quality). Seems no way around dedicated hardware computer interface (e.g. lynx) and, well, much cabeling.

IEEE1394 aka firewire is a nice thing IF it works (e.g. using a lightbridge is really cool once all is up and running and unbeatable in price/value).
Took me quite some time on some machines. Worked right o-o-b with others...issues with pc latform due to ms can be resolved (RME had some very useful instructions on their site. Complicated for developers really, limited cable length etc are drawbacks really.

If you already have a cool running high channel count system, well, a new interfacing method might not be for you. Nevertheless, the option to try an ethernet based one (computer interface cost = 0, hehe, liked that one) really cannot be wrong....

Short status report
from my work on this (WDM PC ethernet audio driver)...
Made a concept paper/todo list for myself to not loose the focus in all those sdk's, DDK's, WDK's...
During research and programming, I read on the dev forums 'bout a guy who already did it to stream audio from win to linux (closed source/commercial), similar model used by motorola to stream to BT headsets, etc, so I guess I am on the right trail now.
I found all the bits and pieces that are needed, but things have to be knitted together now.
Yes, driver development is absolutely no piece of cake, in no way.
I don't know much about the mac and vhdl hardware side of things but i assume things are worse in win driver world.
(learning curve is very steep. highly proprietary and abstract stuff even for people who do or did programming for a living)
Porting to mac might not be much easier than driving mac stuff from scratch.
ASIO: From experience I know asio4all is quite mature in the meantime, I used it once to integrate/'merge' 2 different cards (wdm drivers) and was able to use both at the same time under ONE asio driver. Cool stuff. Very usable under Win....
don't know about asio driver stuff on mac platform...

Unfortunately mac and vhdl hardware developers, excuse me if it sounds odd, may be a bit more on the commercially oriented side of things...(i.e. they know the cost of a man-hour.)
Raphael is right about the hardware side of things, i see no commitments so far reg. fpga development....definitely a show stopper.

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on November 21, 2009, 01:43:23 PM
I think this is a good discussion. ADAT blows. It's limited to 48kHz. We don't run at 48kHz anymore. Yes, 48kHz is good fidelity. But it's still limited. I have been researching firewire for 3-4 years now. Only recently has it come to light that some of the firewire solutions have high CPU overhead. This is bad. Streaming audio via ethernet is a very attractive option. I have been following this one too. I am not a software engineer but I work closely with three of them everyday. Windows drivers are a pain-in-the-ass. Writing any driver (win, linux, mac) can be 6 months minimum. I don't have the money or the skills to do that. So I wait for the industry to develop. Anyways, let's keep this going. DANA.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on November 21, 2009, 02:02:08 PM
Unfortunately mac and vhdl hardware developers, excuse me if it sounds odd, may be a bit more on the commercially oriented side of things...(i.e. they know the cost of a man-hour.)
Raphael is right about the hardware side of things, i see no commitments so far reg. fpga development....definitely a show stopper.

I do FPGAs for a living ...

What's needed is a reasonable definition of the scope of work! then I can tell you how long it'll take.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: audiovisceral on November 21, 2009, 07:26:14 PM
Hi guys,
finally some more interest in the interface discussion, nice!
For all people interested into adat, as said before there already is a solution available with Mikkels board.
So there is no obstacle for you if you want to keep your system like it is and add the hardware.
Up to 48khz. Awsome enough one could immediately start building without any fear there would be no interface available ;-) .
I think this is a good discussion. ADAT blows. It's limited to 48kHz. We don't run at 48kHz anymore. Yes, 48kHz is good fidelity. But it's still limited. I have been researching firewire for 3-4 years now. Only recently has it come to light that some of the firewire solutions have high CPU overhead. This is bad. Streaming audio via ethernet is a very attractive option. I have been following this one too. I am not a software engineer but I work closely with three of them everyday. Windows drivers are a pain-in-the-ass. Writing any driver (win, linux, mac) can be 6 months minimum. I don't have the money or the skills to do that. So I wait for the industry to develop. Anyways, let's keep this going. DANA.

When I was advocating ADAT, I meant SMUX (96 kHz). I too would have little to no interest in a 48 limited ADAT. 96, on the other hand, should IMO be fully satisfactory (and totally plug and play - no drivers required) for the foreseeable future.

Does Mikkel's board allow SMUX?

Also, Tubemooley, the driver writing challenges you mentioned are exactly the reason I think ADAT would be most realistic. Not even a commercial company has released an Ethernet-based unit and they have coders they pay full time for this stuff. If someone's going to volunteer write and support a driver, that would be awesome, but I think it might be a bit over-ambitious and could be setting the project up for failure.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on November 21, 2009, 09:41:48 PM
I think this is a good discussion. ADAT blows. It's limited to 48kHz. We don't run at 48kHz anymore. Yes, 48kHz is good fidelity. But it's still limited.

I'll have to tell Apogee that my AD-16X blows because it's hooked to my DAW via ADAT protocol.

Yikes! ???

I don't think Apogee ever got their Firewire interface for the AD-16X working properly.

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: detonator on November 22, 2009, 02:55:52 AM
I don't think Apogee ever got their Firewire interface for the AD-16X working properly.
Probably depends of what firewire interface is used at the host. The host card needs a TI chipset, otherwise it will never work at all.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Holger on November 22, 2009, 03:16:25 AM
... The host card needs a TI chipset, otherwise it will never work at all.
I had to learn that  :(
It's frustrating. There's only one manufacturer left. Not a good basis for a new project.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on November 22, 2009, 06:35:28 AM
Not even a commercial company has released an Ethernet-based unit and they have coders they pay full time for this stuff.


I beg to differ. There are 3 or 4 ethernet-based audio streaming solutions out there. But the drivers are not circulated freely. You have to purchase the equipment. The latest is from Audinate in Australia. They have licensed it to Lab Gruppen (amongst others) for audio streaming in sound reinforcement applications. Another one is from a subsidiary of Telos. It's called Axia or something. I am not saying that these are ideal solutions. In fact, who can tell because they are basically proprietary at this point. But they are a step in the right direction. And ADAT blows because it's a pain-in-the-ass. Yes, it works and it's very solid. I have 3 or 4 ADAT devices. But when you go into S/MUX mode, you lose half of your channels in that connection. I don't care what Apogee thinks. Tell them whatever you want. I know what I like and what I don't like. I was expressing my opinion. You can poop all over my opinion. I don't care. It's still my opinion and I'm not going to think badly of you for disagreeing with me. That's why it's called a forum. DANA.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on November 22, 2009, 06:58:35 AM
Digigram sells their EtherSound products. Then there's SuperMAC. Sony first developed SuperMAC and HyperMAC which seem to be evolving into AES50. This is a cut-and-paste from www.zpeng.com == "The SuperMAC technology behind AES50 had been developed by Sony Pro-Audio Lab, Oxford, and later acquired by Klark Teknik, who are now making the technologies available on a royalty-free basis. Klark Teknik has selected ZP as an authorized AES50 implementor in 2008. Furthermore, ZP is one of the founding members of the AES50 Trade Association (AES50TA). More information can be found at: http://www.supermac-hypermac.com and http://www.aes50ta.org." == end of quote. Lynx Studio Tech has released their AES16e-50 card recently. ((Good luck contacting ZP. They exist but they don't respond to e-mails. I got them to respond to me once about a year ago.)) DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 22, 2009, 07:38:50 PM
Hi guys,
you threw some interesting information and links into the discussion.
Personally I don't think adat sucks for what it is but for sure there are better things possible.
Unfortunately, Mikkels board does not support smux for now, it was developed for apogee converters that were not capable of 96khz.

Right now i am starting to read about aes50 and noticed already at the first pages, that there are some things I did not think of.
E.g. AES50 is bound to 100-base-t networking max. This is due to definition of RJ45 pin assignments, (gigabit networks have diff. pin assignments! Those are compatible, but the additional bandwidth is not usable in AES50 hardware.)

Andy, great you chimed in!
Since I do not have any protocol details right now and there is already a lynx solution avail, I think AES50 documentation might give an impression of the what has to be done for a proper implementation of such a protocol...
Maybe it's even exactly the way to go, because it is already an open industry standard, OTOH there may be some obstacles to implement aes50 'the software way'.
What frightens me most at the moments is the implementation of clocking on the pc side.....
I did not do such stuff before in any way....
Also, Andy could you maybe take a short sneak view into the opencores.com free implementation of adat and comment on how labour intensive it would be to implement s/mux? That would be of great help as well.

Kind regards,
Martin

BTW, half a year of development time for a functional or even stable driver seems to be a realistic value IMHO....but we'll see.

P.S. there are some more things that firewire sucks at. Not only are the TI chips the most reliable by far (found only one PCI card that worked with the lightbridge without a TI chip). There are problems with the hot-plugging, frying the chips. It is even possible to fry the chips due to reverse insertion! Don't laugh. I fried a lightbridge once due to that. This is easily possible due to miserable quality of some cable plugs and jacks! I did not even think of such a possibility. Due to power distribution in the cable you instantly fry the phy chip.
External powering is dangerous as well. This can fry the computer interface phy...
Nevertheless I love the lightbridge.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on November 22, 2009, 07:55:17 PM
I think AES50 documentation might give an impression of the what has to be done for a proper implementation of such a protocol...

(emphasis mine)

AES50 is great if you want interoperability, which is a good thing seeing how many AES50-compliant products are out there.

AES50 is not so great if you want best throughput, or lowest latency, or something that's very simple to implement in an FPGA, or something that's easy to write a driver for, or an example of a clean protocol.

JD 'design by committee' B.
[AES50 is pretty good if you're studying Business or Organizational Culture and you're writing a thesis on Industry Standards]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 22, 2009, 08:15:07 PM
Haha,
good one, JDB.
You should see my face when I read the AES docs. (Eyes white open most of the time...)
Not an easy task at all for DIY (AES50), but for now, I take it as an example of how it could be done-
I really do not know by now if a proper implementation of the standard is possible to do by software driver+network card or if some changes would make this much easier to realize or even improve practical value.
For me it looks like it's a protocol that allows to sell specialized products to customers with good budgets. (like MADI eh, AES10)...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: wtmnmf on November 23, 2009, 07:50:11 PM
For those wanting to take a look at the AES documents (50,10):

http://www.philippe-lahaye.fr/spip.php?article9&var_recherche=aes
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on November 24, 2009, 05:00:13 AM
Thanks for that link. I just downloaded those doc's. Don't forget..... Cirrus has their CobraNet product too. That's ethernet-based also but I can't remember if it can co-exist on a regular LAN. I don't think it can. I think it needs a dedicated CAT5. I just linked thru Cirrus to these guys..... www.audioscience.com. They have a product using the Axia Livewire protocol mentioned above. This one can operate on a standard ethernet network. Go look at their ASI6585 product. It has Windows and Linux drivers. DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: nielsk on November 24, 2009, 09:12:23 AM
The ADAT interface and 44.1 / 48 K are here to stay, and there is much hardware out there in use and not about to be thrown away, so I see no problem supporting them. I know several top notch engineers and producers that have records out that are currently charting, and NONE of them use anything higher that 48k. EVERY production I have / am working on for TV & film are at 48K.
Yes, higher sample rates sound better, and no, kids listening to MP3s do not care.
IMHO, the remarkable efforts represented here should stay focused on meeting current needs, and if they can grow to accommodate future trends, then all the better. Just avoid the trap of dissolving in pursuit of the next best thing......
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on November 24, 2009, 09:40:12 AM
To me, the next best thing is people that have an integrated ethernet card or two and would like to use it to stream audio data to and from a DIY A/D D/A converter. Possibly while they are connected to the internet. I couldn't care less about ADAT, AES or MADI in that respect; they all require them to buy additional cards or other hardware to make a viable recording solution. While you usually get onboard DSP mixing or some other boon, it comes at a price that I hope to eliminate and make multitrack recording more comfortable (computers abound and there's usually a free port on the router) and affordable. Even if you had to buy an additional ethernet card it's WAY cheaper than a, for instance, AES or MADI card..
Title: Re: Modular multi channel DIY AD/DA Box
Post by: volker on November 24, 2009, 10:07:42 AM
FWIW, this thing here, the USRP2 (http://www.ettus.com/) is a Xilinx Spartan 3 at its heart, using a gigabit ethernet interface to manage it's ADC/DAC data exchange. All schematics and sources are fully available for download. It supports Windows, Linux as well as Mac. Might be worth a look for anybody interested in developping such an interface (or a chat with its designer), unfortunately I know next to nothing about FPGA programming...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 25, 2009, 03:34:24 PM
So, here is a first preview of the AES receiver transmitter board.
Finally I decided to use the DIX4192 because that is the most cost effective solution. The downside is that you need a small microcontroller that sends two or three bytes to the DIX4192 for enabling the receiver port. However, I accept that because you can do that with a small AVR. They only cost 2Eur and everyone can program the internal flash with a PC if the PC offers a RS-232 port (or a USB-to-RS232 converter for 10Eur).
The chips from cirrus turned out to be much more expensive especilly the transmitter.
Tommorrow I'll post the final schematic. Then I'll wait for some days for some remarks on it before I order the first prototype board.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 26, 2009, 01:11:08 PM
Wow, that looks like an affordable but DIY-friendly solution.
I have to check with the datasheets before adding further comment to the final ver.
Thank you posting!

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on November 26, 2009, 04:01:18 PM
Also, Andy could you maybe take a short sneak view into the opencores.com free implementation of adat and comment on how labour intensive it would be to implement s/mux? That would be of great help as well.

The opencores ADAT project has vanished.

I looked at it awhile ago and didn't think much of it. The protocol itself, based on the ADAT patent docs, is really simple and the transmitter is very easy. The receiver is a bit more complicated because you have to extract the clock from the data.

[quote[P.S. there are some more things that firewire sucks at. Not only are the TI chips the most reliable by far (found only one PCI card that worked with the lightbridge without a TI chip). There are problems with the hot-plugging, frying the chips. It is even possible to fry the chips due to reverse insertion! [/quote]

You have to work VERY hard to plug a FireWire cable in backwards. You'll certainly destroy the jack, and most devices don't protect against the power being applied to the wrong pins because the connector is supposed to prevent that.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 27, 2009, 01:40:56 AM
Yes, you are totally right about how hard it *should* be to reverse the plug. Actually, there was a cheap backplane and mainboard jack combination that effectively 'allowed' a wrong insertion easily. I felt so stupid and upset that I did a bit of research in this field and noticed that I am by far not the only one that had this experience. I found several upset statements of people that destroyed high-end cameras this way (requiring hundreds of dollar-repairs). Also, I had a talk with the out-of-warranty service company for m-audio in germany, who told me that destroyed phy's are by far the most common repairs on the firewire audio interfaces, so lack of protection is an issue with firewire really.
Ironically the mainboard was equipped with the well-suited TI chip so I did not even think of how cheap some mainboards are built when it comes to the jacks nowadays. It did not require more force to plug in in reverse than it did the right way on my own computers belkin card. Surely I check orientation twice ever since...
Well, in the meantime I can laugh about this, but I guess that would be different if it had cost me a few hundred dollars more. :D

Kind regards,
Martin
P.S.: The owner told me the jack and mainboard phy still works fine with external equipment, but he threw away all firewire cables with 'soft rubber'-like plastic plugs....lucky basterd he is, hehe ;D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 27, 2009, 05:22:12 AM
Here is the schematic of the AES receiver/transmitter board.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on November 27, 2009, 07:21:20 AM
The DIX4192 is almost pin-compatible with the SRC4392 sample rate converter. It would be useful if the board supported both, as then you could feed a steady local sample clock to the converters and have the SRCs handle the timing domain conversion.

JDB.
[as Bruno Putzeys has pointed out a few times, in that case it's best to have an internal sample clock at an odd rate such as 200kHz and not something close to the external sample rates, in order to minimize SRC artefacts/distortion]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 27, 2009, 10:54:04 AM
Indeed, a good point. I had a short look on the SRC4392 datasheet and yes it is almost pin compatible. After a first view only two pins have to be connected additional (pins that are nc on the DIX4192) and then the SRC4392 works on my pcb. I'll check that and modify the board a little bit the next days (weekend is coming ... :D).

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on November 27, 2009, 04:10:44 PM

From what I know... (And I *should* know) - they are exactly p2p compatible, other than some register changes to enable the src. (The src doesn't exist on the dix part)

/R
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 28, 2009, 04:11:36 AM
Not really. Thr SRC has some functions like MUTE on pins which are not used on the DIX. So you can make the board usable for both by connecting these pins either to ground or to +3V3. More details on that when I further investigated that.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on November 28, 2009, 09:26:26 PM
Awsome work, Raphael. Great idea to have the SRC4392 beeing supported on the pcb with the option to src to an internal clock requirement, just like JDB recommended.
If I understood it right, it would be possible to adjust the internal clock speed to the best sounding sample rate of the da or ad chip. Correct?

Rochey, I guess it is just about what kind of 'compatibility definition' is used (I guess it is depending on the context in this case, e.g. upward or downward compatibility). I'm pretty sure you know your stuff....I lately saw you in a video talking about some awsome chips...

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on December 03, 2009, 09:37:08 AM
BridgeCo has solutions for I2S/I8S <-> Ethernet:

http://www.bridgeco.com/index.php?option=com_content&task=view&id=16&Itemid=36

http://www.bridgeco.com/pdfs/consumer_audio/product_brief_DM850_v2_20080827.pdf

Using I8S I think these (if have the same core as DM1100/1500) can support upto 32 channels in and out.

Their Pro Audio section BridgeCo AG in Switzerland has been moved to ArchWave company lately, maybe you should contact them:

  http://www.archwave.net

  http://www.archwave.net/Audio-Link/Contact.aspx
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 05, 2009, 08:41:58 AM
I've now changed the AES RX/TX board supporting now the SRC4392, too.
I think next week I'll send the gerbers to the pcb factory and let make them the first prototype if there are no ne ideas in the next few days.

Regarding BridgeCo: Is their stuff available in small quantities for DIY projects like this?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on December 07, 2009, 07:50:19 PM
As far as I know, the actual bridgeco chip (870) is based on arm9 with the datasheet only available under NDA.
The predecessor 850 was used in the eary terratec noxon internet radio machine and others.
They use a linux like proprietary RTOS.
I doubt they are available in single quantities. Definitely aimed at the b2b market for time-to-market reduction for media streaming machines. Maybe it can be get in smaller quantities from some southasia chip brokers?
Nevertheless looks like very interesting chips.

PS: Maybe someone from switzerland can make a polite request to bridgeco?

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on December 08, 2009, 05:04:00 PM
Propably these Cirrus components are then easier to get:
http://www.cirrus.com/en/products/pro/techs/T9.html
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 14, 2009, 10:21:16 AM
While waiting for the ordered RX/TX-board, here is the layout of the first AD-module. This has four input channels built around a PCM4204. I've decided to do to first the line input version instead for the mic input because then I can put more channels on the pcb and it makes the box cheaper.
Schematic will follow this evening.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 14, 2009, 06:28:23 PM
And here is the schematic.
Any comments?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on December 14, 2009, 06:45:08 PM
Any comments?

Looks OK, although I haven't compared it line-by-line with the data sheet.

Pity your ground plane has so many slots in it, but that's hard to avoid on a 2-layer. Personally I would have considered wire jumpers over some of the longer breaks.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 14, 2009, 07:11:50 PM
I know, I know.
But I wanted to avoid another source for a wiring mistake or changing to a 4-layer board. I made already a compromise with routing +/-15V and +5V to pin headers on both sides so that I don't had to route them from one border to the other border. Doing so I could route the critical (high speed) lines without crossing a split in the ground plane.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: volker on December 15, 2009, 06:20:05 AM
Hi Raphael,

any specific reasons to not use the internal high pass filter? Since you are dc coupling the outputs of the receiver stages...

Did you think about protecting the inputs of the ADC? With +-15V in the previous stages, the inputs can be easily driven way beyond the maximum ratings.

How do you want to set the low pass filter? Obviously you want the corner frequency to be as high as possible. On the other hand you have different sampling frequencies to choose dynamically. Hmmm. How is that done in commercial units, do they really switch the whole filter?

Concerning the layout: not that I have too much experience in mixed signal design, but one of the first things that comes to my mind is to use separate ground planes for analog and digital. Any thoughts about that?


Please forgive all my questioning, I'm just trying to learn something along the way ;D.


Volker
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 15, 2009, 08:22:33 AM
any specific reasons to not use the internal high pass filter? Since you are dc coupling the outputs of the receiver stages...

No.

Did you think about protecting the inputs of the ADC? With +-15V in the previous stages, the inputs can be easily driven way beyond the maximum ratings.

The evaluation boards of the PCM4204 do not have a protection around the inputs but are driven with +/-15V stages. So I decided that it is not needed. If one of the inputs is overdriven the clip pin will flag that.

How do you want to set the low pass filter? Obviously you want the corner frequency to be as high as possible. On the other hand you have different sampling frequencies to choose dynamically. Hmmm. How is that done in commercial units, do they really switch the whole filter?
I think commercial units have only one filter for all sampling frequencies because you don't see switching relais etc. normally. The question is do these units always sample with the selected sampling frequency or do they use a fixed sampling rate and generate the selected one via a sample rate converter.

Concerning the layout: not that I have too much experience in mixed signal design, but one of the first things that comes to my mind is to use separate ground planes for analog and digital. Any thoughts about that?

Well that is wrong. You should not use separated ground planes for AD/DA conversion. There are many applications notes and even the datasheets state that AGND and DGND should use one ground plane and not two separated planes.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: volker on December 15, 2009, 09:21:01 AM
Quote from: rkn80
Well that is wrong. You should not use separated ground planes for AD/DA conversion. There are many applications notes and even the datasheets state that AGND and DGND should use one ground plane and not two separated planes.

Yes, I just saw the remark in the datasheet related to the ground plane. Will have to read up on that topic.

Quote from: rkn80
The evaluation boards of the PCM4204 do not have a protection around the inputs but are driven with +/-15V stages. So I decided that it is not needed. If one of the inputs is overdriven the clip pin will flag that.

Sure, the clip flag will show too much input voltage, but it will not protect the ADC. The datasheet states 300mV below/beyond ground/VCC as the absolute maximum, otherwise the ADC is likely to be damaged. Also depends on the input attenuator of course. But a little two-diode-package seems to be a small price in comparison to desoldering a TQFP-64. It's also mentioned on page 15, but then the diodes don't appear in the example circuit.


Thanks for answering!

Volker
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 23, 2009, 08:51:42 AM
Short before Christmas the ADC prototype board arrived. As you can see I placed three modules on one pcb so 12 channels in total. The AES RX/TX board did not arrive yet so I'll first stuff and test the ADC board. Hopefully after Christmas I can report some good news.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Igor on December 23, 2009, 09:43:18 PM
Nice PCB layout. Analog and digital grounds use same symbol at schematic, but they separated at pcb, right? :)
Just a stupid question... Matter of curiosity, which clock are you going to use for this beast,
configuration, PLL corner freq., oscillator type, etc.....
Title: Re: Modular multi channel DIY AD/DA Box
Post by: desun on December 24, 2009, 08:28:29 AM
Raphael,

I'm really impressed with your dedication and progress with this, and have been reading the thread with great interest! I look forward to seeing the project completed :)

Keep up the good work!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: radardoug on December 26, 2009, 02:02:25 PM
Hi Raphael,
                  I note looking at the circuit there is no input decoupling, and the inputs will sit at Vbias. Have you thought of that? Are you transformer coupling the input?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mcs on December 26, 2009, 05:28:46 PM
Does Mikkel's board allow SMUX?

Yes. Both the transmitter and receiver should work fine for SMUX also.

Best regards,

Mikkel C. Simonsen
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 28, 2009, 09:46:41 AM
Hi Raphael,
                  I note looking at the circuit there is no input decoupling, and the inputs will sit at Vbias. Have you thought of that? Are you transformer coupling the input?

Hi radardoug,

well it is the idea f the project to give everyone the maximum degree of freedom. So everyone can make a choice which input decoupling is wanted (Transformer, Caps, etc.).

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on December 29, 2009, 01:47:10 AM
Nice PCB layout. Analog and digital grounds use same symbol at schematic, but they separated at pcb, right? :)

That old recommendation of split ground planes has been hopefully discarded. Even the most recent AKM and Analog Devices data sheets say don't do that!

With proper attention to layout, your mixed-signal board with a single unsplit ground plane can be as quiet as necessary.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 31, 2009, 12:02:50 PM
HI,

I've some good news: The first AD-channel is working. Sounds ok so far. I simply connected the I2S-output of the PCM4204 to the I2S input of a SHARC evaluation board and used the DAC on this board to connect a loudspeaker to it. The ADC input was connected to s sinus wave generator and I herad a nice sinus. Checking the important places with an oscilloscope the results were ok.
Next task now to stuff the other channels on the board and a new 12 channel AD-converter is born. ;)
So I'm coming closer to the moment when I put everything into one box and mount it in a rack...  ::)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mcs on January 03, 2010, 08:12:18 PM
If I add the SMUX parts to the OptoRec/OptoGen boards are there any testers? I don't have any "real" equipment to test with...

Best regards,

Mikkel C. Simonsen
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on January 03, 2010, 10:39:20 PM
If I add the SMUX parts to the OptoRec/OptoGen boards are there any testers? I don't have any "real" equipment to test with...

Best regards,

Mikkel C. Simonsen

Hi Mikkel

I'm equipped to test SMUX here, I'm currently running an Apogee AD-16X
through an RME ADAT card which is working great.

I'd be happy to help however I can.

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bachevelle52 on January 08, 2010, 07:47:29 PM
So does anyone have an idea for a clock solution yet? I was thinking about running two 4204's, two 4104's and using the wavefront OPTO boards to interface with a lightbridge. Mikkel said that his opto boards could support S/MUX (i think) so I want to run 8/8 i/o at 24/96. If i read the datasheets correctly, i/we can run 1 4204 as "master," utilizing the SCLK input to create the BCLK and LRCLK signals. (Those pins in master mode are outputs) We can use those outputs to sync the other adc running in slave mode. ( where those pins are inputs.) The same idea applies to the 4104's...i.e. 1 master, 1 slave. Or, can we use the BCLK/SCLK output from the master 4204 to time the 4104's as well. In any case i believe the opto parts utilize a BCLK input so we can time those as well. Someone suggested a clock on a daughterboard, and as i have no other option for clock generation, this will have to become a reality for me. The datasheet for the 4204/4104 states that SCLK be a multiple of Fs. (sample rate). Giving us dual rate sampling mode, at 96kHz; 256Fs= 24.576MHz for SCLK. So, any ideas?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: TheGuitarist on January 08, 2010, 09:36:57 PM
Whats the quality of the AD conversion? Is it the same chip as some other converter out there?

Title: Re: Modular multi channel DIY AD/DA Box
Post by: bachevelle52 on January 10, 2010, 02:07:35 PM
:BUMP: I don't want to see this topic die.....
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on January 11, 2010, 06:35:44 AM
24.576MHz is the clock you want for 96kHz and 48kHz. If yer running at 88.2 or 44.1, then the clock needs to be the "standard" 22.xxxx MHz. Those clock frequencies are always shown in the converter datasheets. Yer on the right track now. I have a 4204 EVM board which I plan to work on soon based on this thread. Keep up the good work. DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 11, 2010, 11:52:30 AM
Whats the quality of the AD conversion? Is it the same chip as some other converter out there?

Well, I think the chips do play in the same league like many professional boxes do. Eg. the ADC in a Digi 003 is a CS5361 (as far as I know) and this chip is rated at 114dB DR and -105dB THD+N. A Digidesign 192 I/O is spec'd at 118dB DR and -109dB THD+N. A PCM4204 is spec'd at 118dB DR and -105dB THD+N per channel without tricks like paralleling ADC-channels. These numbers just to give you an impression. Don't forget it is not the chip only the gives you a clean sound. You have to look on the complete circuit.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on January 11, 2010, 09:35:28 PM
Completely right, Raphael. It is much more critical what happens before the converter chip and in the clock. I have no doubt that a very professional AD can be done with the chips mentioned.

Mikkel, great you joined the thread and generously offer help for an s/mux extension for your circuit!
Unfortunately I might not have the time to be a good 'guinea pig' this time, but I always wanted to see how this might be done with your optorec board (which is great)!!!

To be on the save side there should be an option for two crystals on the clock board, so it would be possible to get all the industry standard sample rates 44.1,48,88.2,96.

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on January 11, 2010, 10:21:15 PM
As for the 48/96khz clock I would suggest following TCXO for low price and wide availability: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=535-9318-1-ND (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=535-9318-1-ND)
Corresponding 44.1/88.2 clock would be a 11.059MHz quartz, due to lack of 22mhz availability from the series at digikey.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=535-9308-1-ND
I guess 20ppm might fit the task well. These quartz's already have been used in some audio clock upgrade stuff with good results.
Hm, for clocking DA I would still prefer src upsampling and using only the 96khz internally, so just one quartz...

Kind regards,
Martin

PS: SORRY, I mixed the series up, these are the TCXO's at +-2.5ppm, they are only slightly more expensive i.e.quite inexpensive related to others or the 'voodo'<=1ppm modules:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=535-9618-1-ND (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=535-9618-1-ND)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bachevelle52 on January 12, 2010, 10:55:13 AM
Thank you SBF for the links.....let me pull the datasheets.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 17, 2010, 06:49:28 AM
Here is a pic of a 12 channel ADC-board. Fully stuffed except the input attenuator because I need to get the potentiometers with the next order from another distributor. For testing I replaced it with a fixed setting on an extra board.
I'm now putting everything into one box and doing some tasks like a master clock for it.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Moby on January 17, 2010, 07:52:40 AM
Looking great  ;)
Quote
Fully stuffed except the input attenuator because I need to get the potentiometers with the next order from another distributor. For testing I replaced it with a fixed setting on an extra board
In which stage is potentiometer? I can't see it on schematics or I missed something?
Regarding sound, do you plan to add some sound samples ?
Thanks for constant progress on this and stay sharp  :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 17, 2010, 08:11:28 AM
Input stage, P101 etc. that are potentiometers, aren't they? ;)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Moby on January 17, 2010, 09:10:51 AM
Input stage, P101 etc. that are potentiometers, aren't they? ;)
I imagine that as a trimm . Sorry.. BTW I don't see any reason for input pot on the ADC stage (just adds some noise)  but it's OK if U like it  ;)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 17, 2010, 09:47:35 AM
Well, it acts like a trim. The idea is that you can use that to set the input sensitivity to the value you want and to match hot and cold by trimming. It is not the idea to use it as an volume controller. And however, if you don't want it you can use the resistors on the board for a fixed setting.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bachevelle52 on January 17, 2010, 11:53:04 AM
Did I read that correctly? You're doing a master clock as well Rafael? Well, a million thanks for all the effort you have put into this project and a million more for sharing it! ;D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Moby on January 17, 2010, 05:10:12 PM
Quote
Well, it acts like a trim
I see , can be useful for dbFS trimming  ;)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 18, 2010, 09:22:32 AM
Quote
Well, it acts like a trim
I see , can be useful for dbFS trimming  ;)

That's what it is designed for.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: pietro_moog on January 24, 2010, 10:49:11 AM
hi guys!
i'm following the thread, but i can't really be helpful.
i thought: there's no way firewire is gonna be a solution for this board, too many problems like
gigantic costs, drivers development, chipset costs, and stuff like these.

So, i found this:
http://www.dv247.com/studio-equipment/apogee-x-firewire-x-series-firewire-card--25247
it could be a solution for firewire ( for people like who don't want an adat bridge)
and since it is a solution developed for stuff like Rosettas and AD/DA16x the drivers are gonna be good.
i guess..


what do you think guys?
i don't know anything about power voltages of this thing, but if we can use it we could kick these converters in the High-End sky..
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on January 24, 2010, 02:10:21 PM
I'm actually still working on an ASIO implementation for audio-over-ethernet. So far, I can send multichannel uncompressed audio between two computers and I'm busy trying to tackle latency, synchronization issues and building the configuration UI. Regarding that, there's a screeenshot attached, it's not nearly final since there's a bunch of settings missing for autodetecting devices on the network and selecting the active NICs, but still, I'm pushing this and it will be available sometime in the future (probably a few months away). When complete, this UI would allow you to route virtual input and output channels to remote device input and output channels. Probably without faders, though if there's a need that could be done as well. In software ofcourse.

With regards to a FPGA chip handling the other side of the story, the company I work for is actually a spinoff of a company that does hitech control systems for physics research like particle accelerators. Needless to say, there's a lot of FPGA programming involved, so I'll try to scrounge someone to at least advise on how the FPGA side could be tackled in exchange for free beers and general geekyness.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: steppenwolf on January 24, 2010, 04:09:30 PM
Hi Raphael!

Your project is really heaven-sent;-) I was really hoping something like that would come up!!
Please correct me if I'm wrong, I'm just thinking loud;-):

I looked over your AD schematic and noticed that you use an attenuator in front of your analog stage.
I think it is unity gain, right? Now the AD should take 6Vpp for 0dbFs or around 8.7dBu.
For me, a good input sensitivity would be 18dBu, so I need 10dB of attenuation. I'd scale the resistors to around 1:3 ratio.
As far as I understand it, those resistors also set the input impedance of the device.
Let's say you are aiming at around 20k diff input impedance that would mean 2*7,5k and a 5k across it.
7,5k==||
         5k
7,5k==||
But those 5k also set the source impedance for your stage to follow, right?
Isn't that kind of high impedance. I'm just wondering if that could be a problem. Isn't it easy to couple noise and capacities affecting the signal due to the high source impedance, or isn't that an issue?
I hope I'm not getting it all wrong ;-)
Best,
Stefan                                                                            
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 25, 2010, 08:39:02 AM
Just a quick note: This weekend I've tested the AD-board with an extra oscillator for the system clock letting one AD generate the clock signals for the I2S lines. Worked fine. I'll now have a look wether I can add a little socket to plug in a daughter board with the oscillator on it.

Stefan, I do not expect problems from the trimming because there is the opamp stage between the input and the ADC. And you have no chance. You'll always need an attentuation stage like this to get a signal that is valid for the ADC (except you'll find a good tranformer that reduces the peak to peak voltage).

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 29, 2010, 11:56:39 AM
Update: I made some minor changes to the ADC-board:
- There's now an additional socket where you can plug in a oscillator daughter board for generating the system clock.
- Some layout changes to minimize the size of the slits in the ground plane.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on January 29, 2010, 12:51:18 PM
- There's now an additional socket where you can plug in a oscillator daughter board for generating the system clock.
Raphael

Is External WC doable with the daughter board?

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 29, 2010, 02:14:59 PM
No. I was talking about the system clock (MCLK in the schematic). This clock is needed if you want that the ADC is the master of the I2S system and shall generate the bit and the word clock.
For external word clocks you need some additional stuff to drive the clock lines of the I2S interface and the ADC's need to be setted into slave mode.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on January 29, 2010, 07:59:53 PM
This clock is needed if you want that the ADC is the master of the I2S system and shall generate the bit and the word clock.

Note that for noise reasons it's better to have the ADC be a slave. As master the transitions on the LRCK/BCK driver lines can couple to the analog part of the chip.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 30, 2010, 05:28:32 AM
Hm, recently I read a note that it is better to set the ADC as master: That will improve the system-wide jitter.  ::)
However, using this sockets does not force a ADC to be a master. So you can plug-in an oscillator and still set the ADC to slave. If that is usefull that you've to decie yourself because it depends on your application.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: pietro_moog on February 03, 2010, 09:47:13 AM
any news?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 03, 2010, 09:54:14 AM
any news?

It's been less than a week since the last update. Give the guy some time.

Hm, recently I read a note that it is better to set the ADC as master: That will improve the system-wide jitter.  ::)

Depends on the scale.

Chip scale: for best jitter performance the ADC(/DAC) should be set as clock slave, to reduce feedthrough and modulation. If the converter chip must be clock master, use series termination resistors and a buffer nearby to reduce the load.

System scale: for best jitter performance the converter box should be set as clock master, as its internal XO clock will have better jitter performance than any recovered clock.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: pietro_moog on February 03, 2010, 10:06:16 AM
i'm sorry, i read 20-1- not 30-1-   

my bad!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 06, 2010, 09:26:41 AM
Hi,

well I have a real life job too with a lot of work. Therefore, the project is sometimes a little bit delayed. Sorry. But here is an update: I now made a box and putting everything together into it. I know from my job that sometimes it can happens when you are making boards with high-frequencies on it that they may work stand alone but when you put them all together they do not work well. So I want to make sure that they can be used to build bigger i/o boxes.
My current configuration is 12 channels in and 24 channels out connected via i2s to a SHARC DSP board.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 07, 2010, 10:40:32 AM
Update: Here is an image of the box with 3x the current version of the ADC board in it. The box is not finished yet but it is working, although some things have to be modified and improvised. But that's normal for a prototype... ;)
Some of the modifications will flow into the revision B of the layout and rev.B I'll release for a group buy (perhaps next week?).
The DAC boards will be mounted next to the ADC board and finally I'll make a nice rear panel with cut outs for the plug. Later I want to replace the SMPS by a better one but for now it is ok.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: pietro_moog on February 07, 2010, 08:26:21 PM
this is super-awesome!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on February 07, 2010, 11:33:56 PM
Raphael

Awesome stuff and thanks for offering us such a great project.

Can I just raise a query with the power supply? My experience of interfaces that have design imperfections is often related to crappy power supplies. Things that come to mind are cross talk between the ADC and DAC's supplies, not enough voltage headroom etc etc.

What do you intend for the power supply?

thanks
Rich
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on February 09, 2010, 06:03:11 AM
I have been following this thread with great interest. This is a really killer project. I will be interested in any group buy for raw etch. Converter performance is influenced by the power supplies. Big shock there. Usually there is +5 VDD to power the digital side of the converter and any other digital IC's. Then there is +5 VCC for the analog side of the converter. Then, if you are running analog opamp circuits just outside the converters, well, they require their own supplies too (duh). Probably +/-15 VDC for those circuits. Now, ideally, those will all be completely independent separate supplies. But in practice, that can be difficult. And then, as we all know, linear supplies are generally more desireable than switchers. But I have found that switchers are more than suitable for use with converters. The noise generated inside those IC's can be far greater than any switcher noise. Careful IC de-coupling is highly recommended. So.... to try to answer the original question..... Multiple options exist especially if we're doing DIY. Check your shelves and pull out whatever will work. If you have nothing on your shelves, go to Mouser or Digi-Key or eBay. Now I have to back-track briefly. I believe Raphael is using the PCM4204 IC here. The VDD for that IC needs to be 3.3v. So there, I just complicated matters. But that's the way it is with a complex design like this. Really nice work Raphael. DANA.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on February 09, 2010, 06:08:27 AM
I just went back and re-read part of this thread. Looks like Raphael is using the PCM4104. And he's probably doing some of the power management on the board. Let's see what he says for power supply requirements. My big mouth got the best of me again. DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: pietro_moog on February 09, 2010, 12:57:04 PM
i hope this thing could become as good as SSL alphalink!
it would be sooo cool to have  8 in & out. i'll make it become an interface with 4 ssl preamp, inserts, 2 phonos, monitoring outputs..
internal analog sum..   


i love SSL sound !
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on February 09, 2010, 03:27:44 PM
i hope this thing could become as good as SSL alphalink!
it would be sooo cool to have  8 in & out. i'll make it become an interface with 4 ssl preamp, inserts, 2 phonos, monitoring outputs..
internal analog sum..   


i love SSL sound !

Exactly. If these converters just "work" as well as the alphalink and we can manage cheap connectivity, like ethernet or USB3... to me that's a dream come true.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on February 09, 2010, 06:25:34 PM
And as Van Halen say "that's what dreams are made of":)

Awesome stuff Raphael.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 11, 2010, 02:24:30 AM
Regarding the power supply:

You need the following voltages: For analog power -15V, +15V, +5V and for digital power +3V3.
The analog +5V are only needed for the ADC. The DAC board has a regulator on board that generates the +5V from the +15V rail.
On the analog board there was no space left for this regulator so I decided to build it externally. Therefore, the DAC board will get an additional pin to supply it with extern +5V too. Then you can decide if you want to use the onboard regulator and mount it or to use only one for all in order to reduce costs by not mounting the regulators on the boards. And finally the revision of the DAC board will get the same pin layout for the headers like the ADC board, so that they become interchangable.

Regarding the power supply itself: As you can see on the image I'm using a SMPS. This SMPS does only provide -/+12V and +5V which is ok but nothing special. I'm using this device always for testing and prototyping and do not have bad experiences for analog circuits except that 12V can be a little bit too less if you want to deal with high voltage peaks (I heard from people who like to drive +24dBu for 0dBfs out of their boxes). What you can't see is that the digital power is coming from the SHARC eval-board and will later be generated by a second smaller SMPS with only +5V output and regulated to +3V3.

Raphael  
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 12, 2010, 03:58:43 PM
Hi,

please note: I've opened a Group buy thread for the ADC boards on the black market. You can find it here:

http://www.groupdiy.com/index.php?topic=37733.0

:)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: seavote on February 12, 2010, 04:55:04 PM
im a little intimidated by this project as im an electronics newbie, but im thinking of giving it a try(when i finally get around to it) . i have one newbie question. will this and /or how does this a/d converter interface with my pc sound card.  s/pdif??
and if so(excuse my ignorance)if i use the s/pdif port on my sound card am i completely bypassing the cards own D/A conversion? ok so thats 2 questions.
you know what they say.
there are 3 kinds of people in the world those who can count and those who cant
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on February 12, 2010, 05:24:54 PM
The A/D and D/A boards communicate with I2S, which then needs to be format converted for usage by your PC. Raphael afaik uses a DSP evaluation board to provide this conversion, while there have been talks about an AES conversion board add-on in this thread. I am slowly working on a way to interface these to the computer via a cheap and simple ethernet cable, or alternatively, USB3.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 13, 2010, 02:54:34 AM
Yes there is already a design for a AES in/out board ready to make. But you can also use the ADAT or S/PDIF receiver and transmitter boards flying around on this forum and on the internet because they all use I2S and you can configure the ADC and the DAC as master or slave on the I2S line. I'm only using the eval-board because it is easy for me and I can concentrate on the device under test because I know that the eval-board is doing it's job. ;)

I also want to do a design a wordclock in/out. I see a certain need for it. Perhaps that will come first because standard interface boards like ADAT and AES are available from other DIY'lers. :) But not sure, depends on my free time the next weeks...

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on February 13, 2010, 09:38:52 AM
I also want to do a design a wordclock in/out. I see a certain need for it. Perhaps that will come first because standard interface boards like ADAT and AES are available from other DIY'lers. :) But not sure, depends on my free time the next weeks...
Raphael

Yes!

External WC is critical for integrating multiple converters.

ADAT SMUX @ 96kHz is all I use here, I haven't seen any interface boards that will allow that.

Some info here

http://www.wavefrontsemi.com/index.php?id=11,10,0,0,1,0#productdocsoft

http://www.wavefrontsemi.com/UserFiles/File/AL_Info/ADATOptical96KAddendum1.0.pdf

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 14, 2010, 06:27:10 AM
Mark,

see reply #202. Mikkel states that his boards do work with SMUX.
Because my boards offer I2S input and output you can connect any digital audio interface you want ADAT, AES, whatever...

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 14, 2010, 06:43:54 AM
Mikkel states that his boards do work with SMUX.

They do, sort of.

As far as I can tell, Mikkel's OptoRec is a direct implementation of the Wavefront ADAT receiver chip. This means that while it will accept S/MUX streams (and set a flag to show the stream is S/MUX), you still need an external converter to multiplex the two 48k channels into one 96k channel. This could be implemented in a CPLD/FPGA, a fast enough microcontroller/DSP or a lot of discrete logic.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jackies on February 14, 2010, 06:53:07 AM
 ::)
Stupid question or not...
Doesn't any soundcard use I2S? Would it be possible to just hack any soundcard and hook these converters to it?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 14, 2010, 06:58:28 AM
Doesn't any soundcard use I2S?

Some do, some don't. Cheaper ones have all-in-one chips with the ADC/DAC integrated in the PCI bus interface chip. While I2S is more prevalent, some cards use other digital formats to talk to their converter chips (mostly left-justified, rarely right-justified). I do believe that the PCM4x04 chips support these modes as well.

Would it be possible to just hack any soundcard and hook these converters to it?

Possible? Sure, if you can find the right traces and manage to solder teeny patch wires and possibly buffers to them. I know I don't have the fine motor skills for such brain surgery, but others might.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 14, 2010, 12:05:01 PM
It is not so difficult to hack a soundcard. Only one condition: The soundcard must use chips where you can find enough info's about on the web. Let's assume your sound card uses a DAC that is fully hardware controlled (no SPI control or whatever) then you can easily figure out which signal type (I2S, left-justified etc) is sent to it and you can add your own device instead of the original chip. There are informations about many standard 'bridge' chips like the envy24 on the web, too. I did susch a hacking once for a card. You only need a little bit courage and the luck to find enough info about the hardware. More difficult is the game if there is some OEM stuff or programmable logic on that card but still doable.
But the main problem is: Normally you don't know enough about the soundcard hardware until it lies on your desk and you can inspect it. So you either need to buy one your you need to risk to destroy your currently used soundcard...  ::)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Laran on February 16, 2010, 01:40:51 AM
Hello,

my first post on the forum - though I've been a lurker for some time, reading, learning and being inspired by all the creative projects being developped here.

I am very interested in th ad/da project, and would actually like to build quite a few channels of it if I can manage it - it is a happy coincidence that this project is reaching critical mass just now when I was looking for exactly this!   ;) :D

I don't have much experience yet with building DIY audio units, but have been wanting to jump in and learn for years.  Now seems like the right time.

I do have some concerns (being new to it all) - while I'm not too worried about the soldering,  I'm not clear on how most of the interfacing is going to work - power supply?  connecting the various boards together?  getting it connected to the computer?  I'd like to get 96k from these converters - how is smux implemented?

Are these things going to be coming down the pipeline?  My main concern is to be left with a stack of beautifully assembled pcbs and no idea how to make use of them.   :D

Is the first batch that is getting ordered up exclusively for the AD right now, with DA to follow later?  and hopefully the other components to get it all running?


Apart from these concerns - congrats and thanks for all the tremendous work that has gone into this project already - I look forward to participating.   :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on February 16, 2010, 03:53:39 AM
Oh for the love of god please build at least a single tubescreamer before attempting anything as sophisticated as a full blown 96khz multichannel AD/DA with SMD sizes!  :o
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on February 16, 2010, 03:58:12 AM
Oh for the love of god please build at least a single tubescreamer before attempting anything as sophisticated as a full blown 96khz multichannel AD/DA with SMD sizes!  :o
Agreed. I've done a few DIY builds but am still going to offload the SMD-ing to someone else who does it for a living. Not that it can't be done, but I don't trust my abilities with something as complex as this one :)

Laran, do you know any electronics guys who repair modern equipment with SMD elements for a living? Maybe get in touch with someone from a local electronics forum or something..
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on February 16, 2010, 06:48:34 AM
Laran

Welcome to the board. Dont be put off with posts that might be a bit blunt and direct. Some members here can actually be very encouraging and nice. I do agree it may be worth your while with a few tiny projects first though-  smd is another ball game.  
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Laran on February 16, 2010, 02:02:59 PM
Hi, thanks for the welcome   ;)

I acknowledge the points raised by all.  I'm no engineer, but I have done a bit of modding and maintenance work and am looking to expand my DIYing activities.  I learn best by doing, and was planning to order one or two extra kits for learning purposes in case I were to somehow completely botch up the first one.  I actually do have a friend who is an excellent tech that does a great deal of work for studios in the area that I could call upon should I find myself overwhelmed.

I'm pretty handy at precision work though and feel I can slog my way through the manual assembly - I just wanted clarification on the chain of components required to go from assembled individual kits to a completed functioning unit. 

Assembling existing designs with some instructions I can do - designing my own solutions is definetly beyond my range of experience right now.   :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 16, 2010, 03:34:37 PM
I do not know why people are always scared by SMDs. The is state of the art, Throug-Hole devices are almost dead.  :(  ::)
By the way my first DIY kit that I did many years ago was already a kit with SMDs. It was an USB soundcard with the main IC in TSSOP case. Suceeded the challange. It is not so difficult it only seems to be. :)

Regarding the interface: Yes there are intefaces to the outside in the pipeline. First of all there are Mikkel's ADAT boards and many S/PDIF boards can be found on the internet. I have an AES interface board ready to make and currently I'm designing a wordclock board which will come before the AES board because I got several messages, that people have an ADAT interface but no good wordclock in/out and no good main clock generation. So the wordclock board will hopefully fill this gap providing wordclock, masterclock (= Superclock in ProTools) and sync to externally applied wordclock.

And yes, all the boards I've successfully built and tested will be offered for a group buy. The only reason for restricting to a certain board is to minimize the risk of confusion. You can be sure that after ADC board a DAC group buy will be started, then wordclock, then AES interface and whatever comes then. There are so much possibilities. Even other people can jump into it and design boards for this box.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 18, 2010, 09:09:38 AM
Ok. I would like to discuss the wordclock module now.
I'm currently busy with designing the circuit. Here is what I specified:
- generate master clock for the box from a crystal on wordclock board
- generate I2S clocks from the master clock
- fan out the clock signals on 6 pins for each clock, each pin buffered so that you can connect many ADCs and DACs to the clocks
- send internal WCLK (wordclock) to the outside via BNC
- send internal MCLK (superclock) to the outside via BNC
The following features are switchable:
- replace/sync internal MCLK by externally applied superclock
- sync to externally applied wordclock
(in both cases the internal I2S clocks are generated from the sync'ed master clock)
- sync to externally applied AES signal

- the design shall use parts which can be easily ordered by a private person. I know that there are some high-precison clock generation and distribution chips but very often it is not so easy to get them in small quantities.
- the design should not use devices which need to be programmed (like MCs or FPGAs)

- the board shall be usable stand-alone: Makes it possible to build a master clock unit without the ADC/DAC stuff.

Anything missing or additional ideas?

Of course a more advanced board can be done later utilising programmable devices but for now I want to keep the board doable also for those who do not have the tools for programming devices.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on February 18, 2010, 11:10:04 AM
I am very interested in the upcoming clock circuit and appreciate the idea of keeping it free from programmable devices first.

I like to link to a small basic clock module that I stumbled upon when looking up suitable crystals (see some posts back). It could be an example how some of the specs could be fulfilled, e.g. easily available parts esp. the crystal. This basic clock core uses a low noise LT regulator to bring down the 5V rail to 3.3V: http://www.awdiy.com/index.php?page=miniclock-v2 (http://www.awdiy.com/index.php?page=miniclock-v2)

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 18, 2010, 03:36:26 PM
- generate master clock for the box from a crystal on wordclock board
- generate I2S clocks from the master clock
- fan out the clock signals on 6 pins for each clock, each pin buffered so that you can connect many ADCs and DACs to the clocks
- send internal WCLK (wordclock) to the outside via BNC
- send internal MCLK (superclock) to the outside via BNC

That's the easy part. Do consider source termination on the BNC drivers, possibly with a jumper(/switch) to short them out.

- sync to externally applied wordclock
(in both cases the internal I2S clocks are generated from the sync'ed master clock)
- sync to externally applied AES signal

That's the hard part, especially if you want to allow syncing to 44.1k, 48k and everything in between while still having good jitter performance. Bonus points for supporting Varispeed (yuck).

- the design shall use parts which can be easily ordered by a private person. I know that there are some high-precison clock generation and distribution chips but very often it is not so easy to get them in small quantities.

That's an admirable goal. Should be doable for parts like line drivers and distribution amplifiers, but I suspect the clock oscillator itself is safer to implement in a pre-canned version than as a discrete design due to the sensitivity of component variations and construction.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 18, 2010, 04:11:22 PM
That's an admirable goal. Should be doable for parts like line drivers and distribution amplifiers, but I suspect the clock oscillator itself is safer to implement in a pre-canned version than as a discrete design due to the sensitivity of component variations and construction.

I do not exactly understand what you mean eith a pre-canned version. For the design I'm doing (like most of my diy projects) the decision for components is made by the question. "Can I get the part from one of the bigger distributors liek digi-key or Farnell or do I have to order it in quantities of 1000pcs." If the last is the case I do not use the part... ;)
That is the rule for the wordclock module too. Therefore I decided to use an good oscillator and to derrive the needed clocks from it via a clock divider circuit. I don't want to use a PLL170x from TI or the clock generators from Cypress. I think a good crystal oscillator will outperform a PLL chip.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 18, 2010, 04:31:58 PM
I do not exactly understand what you mean eith a pre-canned version.

This (http://www.tentlabs.com/Components/VCXO/index.html) is a pre-canned crystal oscillator, this (http://www.qsl.net/dl4yhf/dcf77_osc/index.html#homebrew_ocxo) is a discrete one. I suggest you go with the former.

That is the rule for the wordclock module too. Therefore I decided to use an good oscillator and to derrive the needed clocks from it via a clock divider circuit. I don't want to use a PLL170x from TI or the clock generators from Cypress. I think a good crystal oscillator will outperform a PLL chip.

No question about that.

But you said that you also wanted to allow locking to external word clock. I would urge you to specify the intended capture range, as that will not only have a major impact on the rest of your design but it'll also help people determine if your clock module (and with it the entire converter) will be usable in their intended applications. That's especially good to know given that we're at the board-ordering stage of one of the subsystems.

JDB.
[have a bit of a fever, so I might not be expressing myself too clearly]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 19, 2010, 03:20:42 AM
Ah, ok. That what you call a pre-canned crystal oscillator I wanted to use, too, because that are those devices which I call easy to get. :)

Regarding locking on wordclock. I was thinking of capturing the range between 32kHz and 96kHz. About 192kHz I'm a bit unsure wether it is useful or not. I know that ADAT supports that vie SMUX IV but is it used by any soundcard? Same thoughts about AES. Is 192kHz multichannel output really in use? Or shsould we think of a more sophsticated board with a fpga or microcontroller on it if you really wnat to have this high-quality 192kHz signals.
But for this board it is important to find a good balance between features, price and effort to build it.

Get well soon, JDB!

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on February 19, 2010, 06:26:59 AM
All of this sounds very good Raphael. I have added my responses IN CAPITAL LETTERS for what I need in my studio. This is just what I need. Other people have other needs. Just trying to contribute. DW.

Here is what I specified:
GOOD - generate master clock for the box from a crystal on wordclock board
GOOD - generate I2S clocks from the master clock
VERY GOOD. ABSOLUTELY NECESSARY - fan out the clock signals on 6 pins for each clock, each pin buffered so that you can connect many ADCs and DACs to the clocks
DON'T NEED - send internal WCLK (wordclock) to the outside via BNC
DON'T NEED - send internal MCLK (superclock) to the outside via BNC
The following features are switchable:
GOOD BUT DON'T NEED - replace/sync internal MCLK by externally applied superclock
DON'T NEED - sync to externally applied wordclock
GOOD (in both cases the internal I2S clocks are generated from the sync'ed master clock)
ABSOLUTELY POSITIVELY NECESSARY - sync to externally applied AES signal

Sync/lock to externally applied signal up to 192kHz is good but not 100% necessary. We run at 96kHz these days but our RME and Lynx cards and some of our external converters will operate at 192kHz. And like JDB said, pre-canned oscillator is the way to go.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on February 19, 2010, 10:37:09 AM
If you're going to sync to external clocks, you should include a WC In option.

In studios with more than one converter or a WC generator it's a necessity to get
them running in sync.

Beyond 96kHz is not a concern here.

In my list, WC IN is in capitols.  8)

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: seavote on February 19, 2010, 11:11:31 AM
up till now i have only used $200-$300, 2-4 I/O sound cards. home studio to record myself and friends. from researching the internet i understand (correctly or incorrectly) that their is not much difference in audio fidelity in cards in this price range, but the A/D converters on higher end $$$  (apogee.lynx) are a vast improvement over the cheaper cards. if i build this project how much of an improvement can i expect to hear? is this on par with the stuff used in major studios,somewhere in between or i wont hear much of a difference from my m-audio card unless i listen really hard?  sorry for the divergence from all the tech talk (that i dont understand.....Yet!) but i forsee a great effort i my part to understand this circuit and im weighing whether it will be worth the effort in audible terms. i know learning is always a good thing but i have a staggering amount to learn about analog circuits allready. that said: rkn80 thanks for sharing a great project with others.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on February 19, 2010, 11:16:17 AM
on the actual converters, yes, there is a signficant performance different. PCM4204 and PCM4104 are not used in toys.  ;)

What will make the biggest difference is the power supply and the clocking structure.

Insisting that the ADC itself is driven from it's own clock, and not PLLing to another master will make a huge difference.

Raphael - don't think I'm not watching this thread!  ;) Good Luck!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: nielsk on February 19, 2010, 11:18:27 AM
EXT WC in is an absolute must in all but the most analog dominated dominated situations. Any piece of digital gear is incomplete without it.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 19, 2010, 11:35:31 AM
ABSOLUTELY POSITIVELY NECESSARY - sync to externally applied AES signal

In my list, WC IN is in capitols.  8)

EXT WC in is an absolute must in all but the most analog dominated dominated situations. Any piece of digital gear is incomplete without it.

OK, so it would appear that people want to be able to sync with external clocks, be it AES or WC.

If I were designing this clock board, I would find it very useful to know how much lock range you folks require. Do you need full-range any-rate locking to any odd sample rate between 32k-192k, including oddballs like say 46.37ksps, or would it be sufficient to be able to lock to fixed incoming rates at 44.1/48/88.2/96/176.4/192ksps +/- 100ppm?

(Sure, in kid-in-a-candystore mode all of us would love full any-rate support, but it would make clocking much more complex and/or jittery)

JDB.
[I for one do mostly live location recording, running off my own clock, and the few times I have to deal with external digital streams and/or timecode I use Mr. ASRC, so for me personally external sync is Not An Issue]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 19, 2010, 11:38:51 AM
Raphael - don't think I'm not watching this thread!  ;)

Uha, what a threat! :D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 19, 2010, 12:13:03 PM
JDB,

is it really that important to know which rates will occur? Let's assume we have a circuit that always multiplies the incoming wordclock by 256. Then you always have a masterclock dependent on the incoming clocking. From this master clock you then derrive the bit and the frame sync clock of the i2s and with these three signals you drive the DAC or the ADC or what ever. Due to this master, bit and frame sync clock have now a fixed relationship: MCK = 256fs, BCLK = 128fs, LRCLK = fs. If fs is 48kHz then the clocks are exactly that what is needed for a PCM4204 in single rate mode. For fs = 44.1kHz it is exactly the same scheme. So it seems to me that the ratio between the clocks is important (and this scheme is changed for double and quad rate mode).  The data sheet states that the PCM4204 supports master clocks between 6.144 and 38.4MHz for single rate configuration. So now let's assume we do not have exactly 48kHz but 47kHz. Then the master clock will be 12.032MHz instead of 12.288MHz but the PCM4204 will still lock on it. So it doesn't matter which frequency is coming in for the generation of the i2s clocks.
From a project some years ago I know that you can vary your master clock in a certain range and as long as the relations between the i2s clocks are ok your system will work because everything is "in tune" (of course there are limits and surely at a certain point the clock detection in the chips will be confused...).
So in fact everything is derrived from your incoming clock signal any change in the wordclock rate also occurs on all clocks keeping them still in the correct relation. Then you don't have to care about the rates so much. But you have to find a way to deal with the jitter on the incoming signal and get it free from jitter as much as possible because the jitter will then also affect the master clock and from there all other clocks and finally the whole system.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 19, 2010, 12:28:50 PM
is it really that important to know which rates will occur?

Yes.

The area where it matters a lot is jitter. Very simply put, the higher the Q of the frequency-dependent element of an oscillator the lower the phase noise and thus the lower the jitter. However, the wider the required tuning range the lower the Q, and thus the higher the jitter.

If you limit yourself to 44.1/48k and multiples +/- 100ppm, you can simply have two pre-canned VCXOs (one at 22.5792MHz and one at 24.576MHz) to cover all needed frequencies. This plus a (reasonably) simple PLL leads to a DIYable design where the clock jitter does not limit the converter's performance.

If you need to cover the whole range in one go you have to sacrifice either performance or simplicity. On one end of the scale is a simple 4046-based PLL using its internal VCO, with jitter performance as bad as a few ns. On the other end of the scale you can get down below 10ps jitter with a careful digital synthesizer (DDS) with clever spur cancellation, but that's hard to build and calibrate even for those of us who do have an electronics lab at our disposal. And even then the VCXO has better performance.

JDB.
[we've gone over it in other threads before -- for best performance with this class of converter chip you do want to keep jitter below 10ps]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on February 19, 2010, 01:25:08 PM

[I for one do mostly live location recording, running off my own clock, and the few times I have to deal with external digital streams and/or timecode I use Mr. ASRC, so for me personally external sync is Not An Issue]

i second this.. i'd prefer to ASRC and leave an ADC run from it's own oscillator, instead of slaving it to a jitter WC+PLL.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on February 19, 2010, 01:34:58 PM
ABSOLUTELY POSITIVELY NECESSARY - sync to externally applied AES signal

In my list, WC IN is in capitols.  8)

EXT WC in is an absolute must in all but the most analog dominated dominated situations. Any piece of digital gear is incomplete without it.

OK, so it would appear that people want to be able to sync with external clocks, be it AES or WC.

If I were designing this clock board, I would find it very useful to know how much lock range you folks require. Do you need full-range any-rate locking to any odd sample rate between 32k-192k, including oddballs like say 46.37ksps,

Without getting into religious issues regarding external clocking I would say yes.

In addition to the standard rates (I go as high as 96kHz in my productions). I make use of the option in my WC generator to do vari-speed. Anyone coming from a world of analog knows how useful and valuable VSO can be in a production. Rarely, if ever would I go below say +/-1.5kHz.

Other folks may have different requirements.

And while I'm aware that we're not designing a commercial product, the bottom line is:

External clocking is used everyday in thousands of studios.  8)

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 19, 2010, 01:50:57 PM
Without getting into religious issues such regarding external clocking I would say yes.

What do religious issues have to do with anything? As far as I'm concerned the arguments here are purely technical.

In addition to the standard rates (I go as high as 96kHz in my productions). I make use of the option in my WC generator to do vari-speed. Anyone coming from a world of analog knows how useful and valuable VSO can be in a production. Rarely, if ever would I go below say +/-1.5kHz.

Then for your application there's a problem. That's not meant as a judgement on value or validity, just a technical observation.

As far as I can see, there are three DIYable clock sync paths:

1) VCXOs with a simple PLL. Cheap, best performance, but limited to +/-100ppm tunability.
2) Wideband PLL (like in the Behringer ADA8000). Cheap, crap performance.
3) Wideband PLL coupled with ASRCs. Good performance (slightly less than option 1), more complex implementation, more expensive (Rochey's masters have nice ASRCs, but they cost more than the converters, and can be hard to get). A microcontroller is required to program the ASRCs.

Anyone see a fourth option?

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Biasrocks on February 19, 2010, 02:20:47 PM
What do religious issues have to do with anything? As far as I'm concerned the arguments here are purely technical.

Quote from: http://catb.org/jargon/html/R/religious-issues.html
religious issues: n.

"Questions which seemingly cannot be raised without touching off holy wars, such as “What is the best operating system (or editor, language, architecture, shell, mail reader, news reader)?”

Perhaps the expression is a bit old school.  ;D

I use my ears for a living; ears are certainly technical marvels but sometimes they like something that sounds less than perfect from a technical point of view.

It's great that you've avoided the lengthy discussion/wars on ext WC's.  8)

Mark
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 19, 2010, 02:43:02 PM
Perhaps the expression is a bit old school.  ;D

I'm well aware of the meaning (and of the Clocking Wars), but I wasn't interested in going there. All I'm trying to say is that for a cheap/simple (DIYable) implementation one would most likely have to decide between accurate and flexible. At that stage it might make sense to get an idea of how many people are interested in either before going ahead (or to see if there's a Plan B).

JD "can't get what you want 'till you know what you want" B.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Svart on February 19, 2010, 02:55:08 PM
JDB, how would you feel about putting together a tiny MCU(or small FPGA)/DDS setup for clock generation?  You could simply have the MCU/FPGA run a state machine looking for key presses and then shift out registers to the DDS that set it up for certain frequencies.  that way you can have a default clock, then with a single button can change clock speeds.

The DDS that I've used is the AD9911 and can do DC-200Mhz in sub-Hz increments with extremely good close-in phase noise.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Svart on February 19, 2010, 03:03:24 PM
Also,  I haven't really even read this whole thread..  Why not simplify and just use a codec for each channel?  AKM codecs, like the ones used in the Alphalink lineup, are cheap and easy to use with both ADC and DAC on die.

Anyway, this is a cool project.  I wish I had kept up with it and been more a part of it.

Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 19, 2010, 06:56:40 PM
JDB, how would you feel about putting together a tiny MCU(or small FPGA)/DDS setup for clock generation?

Well...

I've thought about it on and off for some time. I would probably use one of those newer 1GHz SAW oscillators driving an AD9912 driving a bandpass filter with an AD951x clock distributor. Add a microcontroller, a cheap TCXO for an absolute frequency reference (the SAW has good phase noise when compared to the ref multiplier in the DDS, but not-so-great long term drift) and options for digital readout/control. Possibly add a few LVPECL->CMOS translator dongles so you can run a balanced clock to the converter(s) over twisted pair and only go single-ended at the chip's own ground reference. This offers milliHertz-level frequency tunability over a wide range indeed, will VariSpeed all you like, with jitter performance to rival the best canned fixed-frequency oscillators.

However, I don't need one myself, and this kind of tech complexity gets close to 'day job'-levels. Add the fact that you'd need two maybe three complex components in CSP/QFN and home-soldering is out, so someone (ie: me) would have to build and test them. Even at friends-and-family rates the module cost would be at or over $200 (and add up the cost of the major parts I've mentioned earlier and see how close you get...), and at that price I wouldn't blame anyone who pointed out that you can get an entire ADA8k-class converter for the same money.

Or am I being overly pessimistic?

JDB.
[yes, I know the boo-tique CD clock upgrades cost as much and offer way less performance]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on February 19, 2010, 08:26:53 PM
1) VCXOs with a simple PLL. Cheap, best performance, but limited to +/-100ppm tunability.

Not to ruin anyone's party but keeping in mind the general level of this forum, I would choose this option. Easy to get the parts, and least things to go wrong. Because for many, they will.

There are commercial solutions for those who wish for more exotic clocking.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on February 19, 2010, 08:32:42 PM
Noob question:

What is the reason for having other sampling rates other than the usual 44.1k, 48k, 96k etc....?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on February 19, 2010, 10:04:04 PM
Well, I had a varispeed capable soundcard and didn't use the feature at all, not even testing....
In live recordiing, things may be different though...?
Personally I could easily live with 44.1/88.2kHz. I guess lots of people need 48kHz/96khz for compatibility to other gear or delivery formats, too.
I would not need varispeed and be totally happy with option no 1.

(Nevertheless I find the varispeed approach of JD extremely interesting from the technical point of view, maybe because it is far over my head to even imagine what it takes to properly implement such a solution...while he obviously does...)

I also had a head-up when the AKM codecs were mentioned. Quite tempting....I did not realize the Alphalink uses codecs and clocking is some kind of 'half as complicated' from the DIY point-of-view.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Svart on February 20, 2010, 02:15:54 AM
JDB, how would you feel about putting together a tiny MCU(or small FPGA)/DDS setup for clock generation?

Well...

I've thought about it on and off for some time. I would probably use one of those newer 1GHz SAW oscillators driving an AD9912 driving a bandpass filter with an AD951x clock distributor. Add a microcontroller, a cheap TCXO for an absolute frequency reference (the SAW has good phase noise when compared to the ref multiplier in the DDS, but not-so-great long term drift) and options for digital readout/control. Possibly add a few LVPECL->CMOS translator dongles so you can run a balanced clock to the converter(s) over twisted pair and only go single-ended at the chip's own ground reference. This offers milliHertz-level frequency tunability over a wide range indeed, will VariSpeed all you like, with jitter performance to rival the best canned fixed-frequency oscillators.

However, I don't need one myself, and this kind of tech complexity gets close to 'day job'-levels. Add the fact that you'd need two maybe three complex components in CSP/QFN and home-soldering is out, so someone (ie: me) would have to build and test them. Even at friends-and-family rates the module cost would be at or over $200 (and add up the cost of the major parts I've mentioned earlier and see how close you get...), and at that price I wouldn't blame anyone who pointed out that you can get an entire ADA8k-class converter for the same money.

Or am I being overly pessimistic?

JDB.
[yes, I know the boo-tique CD clock upgrades cost as much and offer way less performance]

 ;D

Not overly pessimistic.  BUT I used an 8051 to control a 9911 which used a 500mhz LVPECL clock source.  Remember me telling you about the SIlabs SI530 clock?  Thing of cheap beauty she is.  You can get them in 1ghz now too.  They only went up to 500mhz when I was designing one into my tuner.

8051(or Actel Igloo): <5$
AD9911: 20$
SI530: 15$

You could probably go for a DDS with less functionality to save some cash too.  These AD parts are EXTREMELY sensitive to their reference clocks, much more so than their datasheets would suggest.  Tweaking their loopfilters didn't help much either.  This was before finding the Silabs parts.

That setup has phase noise lower than my EXA can measure.


Yeah the alphalink uses a bunch of stereo codecs.  They spec the same as their high-end chips but are easier to use.  Sounds like a win-win to me.  SSL/Sydec didn't fool around with this design, it's damn fine in it's simplicity and elegance.  They use an FPGA to control it all.  Looks like the clocking and division are done by the FPGA too.  They have some XOs that trace right to the FPGA and the clock lines from the codecs trace to the FPGA too.  Strange, cause I always thought this was a HUGE NO-NO.  I suppose you could do it if you can ensure a clean output.  There is no telling what they stuck in that FPGA.

Oh they also use a nice fat open frame switcher in the box too, an off the shelf part.  Didn't recognize the brand though.  probably some OEM company.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 20, 2010, 07:52:25 AM
Just a note: The AD9911 costs in Germany already 46Eur.
There is no doubt that you can make a design that outperforms many commercial designs but you have to put a lot of effort and money in it. If anyone wants to do that, feel free to do so.
Anyway I like the discusssion about the optimal wordclock implementation. I gives ideas for projects in the future. For now and a more easier to do design I think the CS2xxx family is a good choice, because you can use them without controlling it by a MC.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 20, 2010, 08:11:58 AM
I think the CS2xxx family is a good choice

I would strongly recommend against using those. Their practical jitter performance is on the order of a few hundred ps, which might be barely enough for consumer DVD players (their target market), but it will greatly compromise the performance of the converters you use.

JDB.
[rule of thumb: if it's an IC and it has an internal (VC) oscillator, it has too much jitter. There are some exceptions, but they are few and far between]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 20, 2010, 08:15:49 AM
Hu,

datasheet states: CS2300 period jiter 35ps rms, 50ps rms base jitter, 150ps rms wideband jitter. That's better then many PLLs have.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 20, 2010, 08:41:18 AM
datasheet states: CS2300 period jiter 35ps rms, 50ps rms base jitter, 150ps rms wideband jitter.

Yes. And what you're looking for is <10ps jitter.

(Plus those are ideal-case figures; last time I measured I got rather higher numbers -- but Cirrus isn't unique in that regard)

That's better then many PLLs have.

Yes. And that's why you can't use a generic PLL here.

(A first-order estimate of jitter impact can be found here (http://www.groupdiy.com/index.php?topic=20261.msg238038#msg238038); Bruno Putzeys has published an AES paper that goes into (much) more detail).

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 20, 2010, 09:32:53 AM
After carefully reading the last few replies I've a little bit the feeling that we're talking about different things. So I'ld like to clarify.
I'm still looking for a nice solution for the external wordclock sync. The solutions with the AD991x devices are fine for a VariSpeed design and I think I would definitly go for something like that for a VariSpeed design. There you can't avoid a microcontroller solution because you need to control the DDS somehow. But I don't see how to use these implementations to get a clock signal that is synchronous to an incoming wordclock signal because the AD991x devices expect a much higher clkin than a wordclock. And that's where I was thinking of let a CS2300 come in.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 20, 2010, 11:08:27 AM
I'm still looking for a nice solution for the external wordclock sync.

Yes, I get that.

The solutions with the AD991x devices are fine for a VariSpeed design and I think I would definitly go for something like that for a VariSpeed design. There you can't avoid a microcontroller solution because you need to control the DDS somehow. But I don't see how to use these implementations to get a clock signal that is synchronous to an incoming wordclock signal because the AD991x devices expect a much higher clkin than a wordclock.

You use a PLL.

As you probably know, a PLL (http://en.wikipedia.org/wiki/Phase-locked_loop) essentially is a control loop around an oscillator, using a Phase Detector or Phase/Frequency Detector (PFD) and a Loop Filter to lock the oscillator's phase and frequency to (a multiple of) the reference input.

For us, the reference input is WC in (AES is possible too, but let's not muddy the picture), and the oscillator drives the converter's MCLK.

In the DDS scenario you feed both the DDS output and the WC input to the microcontroller. The microcontroller then implements a PFD, either in software or helped by one or two external D-flipflops. The microcontroller also runs a digital loop filter, and adjusts the phase and frequency of the DDS to match the incoming word clock.

In the VCXO scenario the VCXO gives you the converter's MCLK and (after a divider) an internal WC. If you want to lock to an external WC, you feed both the internal WC and the external WC to a PFD, the output of the PFD goes into a (possibly analog) loop filter which then drives the voltage-driven tuning input of the VCXO. If you have all the polarities and time constants right, this will lock the VCXO to the incoming word clock.

Or were you talking about something else?

(One big advantage of a PLL-in-software is that it is much simpler to implement a dynamically changing loop filter, so that you can have a wide bandwidth for fast capture changing into a narrow bandwidth for best phase noise. But maybe that's a bridge too far for a DIYable implementation).

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 20, 2010, 11:18:18 AM
8051(or Actel Igloo): <5$
AD9911: 20$
SI530: 15$

...and about 20..30dB higher phase noise than the $50 SAW + $50 AD9912. (Did you test whether the Si530+AD9911 had better phase noise than a good 100MHz XO + the 9911's ref multiplier? Looking at the data sheets I expect it would be equal or worse).

Call me a perfectionist, but that 1GHz SAW oscillator gets awfully close to the performance of the Wenzel ref kit they used to spec the 9912, and that sounds mighty appealing. If we must solder LFCSPs I'd rather shell out some more bucks and do it just once with no nagging need to go upgrading later.

JDB.

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 20, 2010, 05:23:58 PM
JDB,

ok I see, we're talking about the same. Sorry. My fault. I had the impressions that the discussion tends more into a VariSpeed clocking then wordclock sync.
I'm still a little bit scared by a software PLL. While I would not have a problem with it because I've some programming devices for different controllers I suspect that this is to far beyond the means of many DIYers. I think the limit is something easy like a ATtiny because these devices can be easily programmed via PonyProg and a serial interface by almost everyone with a PC. So it might be ok to use such a device to control something via I2S. But for an accurate software PLL you might need a more sophisticated MC and very often you need special programming tools to  program them via a JTAG interface. Or do you think that the PFD can be implemnted on a ATmega?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 20, 2010, 06:06:46 PM
Or do you think that the PFD can be implemnted on a ATmega?

That's actually what I would use.

I'm unsure how to judge the programmability-barrier. I work with these devices on a daily basis, so I even have a USB-ISP programmer in my home lab. Cost me all of 30$ off eBay. If that's too much money, there's PonyProg (and a few like it), but does that require a 'real' serial port or are USB dongles supported as well?

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 20, 2010, 06:20:06 PM
I agree with you that using a microcontroller makes it much easier to design because then you can do something like Apogge's Big Ben: Drive a DDS (like already suggested) and implement the PFD in the digital domain.
I'm quite unsure about the programming barrier, too. Like you I have to program devices like DSPs and microcontrollers for my job and I have the programming tools for the AVRs at home. So for me it would not be a problem doing so.
Another idea would be to offer pre-programmed chips for those who cannot flash a microcontroller themselve.
Anyway: I think you cannot feed the MCLK from the DDS directly into a ATmega but you could pick it up directly behind the divider network and compare the wordclocks.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 21, 2010, 12:14:07 PM
I spent this Sunday afternoon with reading about DDS chips. It's all nice as long as you don't think about how to build such a board yourself. I'm not really scared by SMD but a LFCSP package is definitly nothing to be soldered by everyone. While the pads could be done the inner big pad is more difficult because it has to be connected to the ground plane. The only idea I'ld have is to make a hole under the pad and put some tin-solder in it hoping not to produce shortening between the pads. (Of course there is the alternative of giving it to a company, but that makes only sense for bigger quantities, otherwise the price will become so high that you can already go and buy a commercial clocking device for your rack I think). So I think the risk is simply to high because the AD9911 and AD9912 cost a lot of money.
JDB did you already solder a LFCSP and if so ,how?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 21, 2010, 01:41:53 PM
It's all nice as long as you don't think about how to build such a board yourself.

I would agree.

I have soldered boards with LFCSPs (and QFN and the like), but I use a stainless steel stencil to apply solder paste and then reflow on a hot plate. Even then it's not hard to screw up.

For low jitter you want high DDS voltage/current output and high DDS output frequency (to get the highest slew rate), and a high DDS clock to have some distance to the spurs (see AN-823 (http://www.analog.com/static/imported-files/application_notes/475354741144165304775709740692131461831AN823_0.pdf) for details). The DDSes that you'd want to use for this clocking application all come in LFCSPs, with the possible exception of the AD9910 (100-TQFP). Even so there are some reports that the greater lead inductance of that package negatively impacts its performance. And the clock divider/distribution chip (AD951x) is another LFCSP part.

I'd say that the most viable DIY solution would involve not a DDS but a (pair of) VCXO(s), with either a discrete or microcontroller-implemented PFD.

JDB.
[and I don't know of any cheap evaluation boards that could help here, either]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on February 21, 2010, 05:15:08 PM
Quote
I'd say that the most viable DIY solution would involve not a DDS but a (pair of) VCXO(s), with either a discrete or microcontroller-implemented PFD.]I'd say that the most viable DIY solution would involve not a DDS but a (pair of) VCXO(s), with either a discrete or microcontroller-implemented PFD.
I second that. I guess there are not many if any people on this board willing to try mounting LFCSPs at home and reflow them on a hotplate, even if they tried that experimentally before. Especially if more than one of them have to be stuffed on the pcb.
I tried reflowing once and it worked with a household plate, but it was just one cheap component on the pcb and I needed a few trials until i was satisfied with the result.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Svart on February 21, 2010, 10:40:51 PM
JDB, while I don't remember the phase noise numbers from the DDS I do remember the phase noise numbers out of our PLL which is driven by the DDS.  The PLL arrangement didn't equal the phase noise of my Agilent sig-gen although, it was lower than most low phase noise oscillators available.  Looking at a Triquint SAW osc, the 100hz phase noise of the SAW is higher than our design by 15db while it's 1k and 10k numbers trump our design by 5db and 10db respectively and that's compared to the output of our PLL.  For our DDS, I'd say that the 100hz number is probably about 5dB lower than our PLL output while our 1k and 10k are probably at least 15-20db lower out of the DDS compared to the PLL output.  I know that our PLL dominates the phase noise at those points.

Of course you'll have to take this with a grain of salt because it's not apples/apples.  We did a LOT of work getting those numbers from our PLL(ADF4113).  Currently(no pun intended) we get -93,-93,-115 at 100, 1k, 10k respectively.  We are essentially at the limit of the 4113.

Also keep in mind we weren't looking at jitter per se either.

If I get a chance I'll throw the setup on the EXA and take a measurement.


Silabs makes a programmable part that is on par with the 530.  It takes I2C and it's essentially a canned PLL/VCO(like all of their parts).  I think it's the SI570 but I'm not sure.  Don't know what frequencies you need either but you'd likely not get anything lower than 10M from silabs.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 22, 2010, 07:36:41 AM
Hm, I don't want to give up here. What about the following design: DDS: AD9954 puts out a master clock (depending on performance either 24.576MHz or a multiple of it). Clock signal feed into a clock divider getting the internal wordclock. The internal wordclock is sent together with the external wordclock into a phase detector made of two D-flipflops. The outputs of the D-Flipflops are connected to an ATmega88 which also controls the clear pins of the D-FFs. The ATmega talks to the DDS via SPI and regulates the output clock with respect to the values got from them phase detector. With this setup we have a system that is doable because the ATmega88 can be flashed without having high-priced programming tools.
The AD9954 comes in a TQFP48 package which can be soldered by hand. Looking at the spec'ed SFDR (=>responsible for jitter) the AD9954 should play in a similar league like the AD9910 but it is not so expensive like the other DDS (with features you don't need) in TQFP. I think it gives a good balance between performance, costs and difficulty. My second choice would be the AD9858 but this device costs 54Eur while the AD9954 costs 26Eur. That makes it more attractive for a DIY project I think. Of course if we have a working design we can always think of making a higher performing design using one of the expensive devices.
Where I'm quite unsure is the clock divider especially if we have higher clock rates then 24.576MHz. I'm not sure yet, wether I want to use a 'standard' synchronous counter (cmos logic) or a special divider like AD9515 (which comes again in a LFCSP).  I know that some counters can be really noisy...

Raphael
 
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 22, 2010, 08:17:00 AM
Looking at the spec'ed SFDR (=>responsible for jitter) the AD9954 should play in a similar league like the AD9910 but it is not so expensive like the other DDS (with features you don't need) in TQFP.

While it will function, the performance with the AD9954 is much worse than with the AD9912 or even the AD9910. This is partly because of the lower max clock frequency and partly because the 9954 is two generations older, and in the meantime much has been improved wrt spur performance. This is easier to see in the raw spur plots than in the SFDR numbers.

The ham radio community has done a lot of work in characterising DDSes lately, and while not all is directly applicable to audio clocking much of it offers interesting background. This (http://www.xs4all.nl/~martein/pa3ake/hmode/dds_intro.html) is a good starting point.

Dividers are important, but a good squarer/limiter is at least as critical. The AD951x range offers both.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 22, 2010, 08:43:58 AM
How much worse would it be with respect to the jitter?
Btw. I think iClocks have a DDS with a main clock <200Mhz in it. I think I've seen that note somewhere on their homepage.

Raphael  
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 22, 2010, 09:44:52 AM
How much worse would it be with respect to the jitter?

Enough.

The main issue are the spurs. The ham radio folks using the older DDSes in Software Defined Radio have algorithms to re-tune the DDS a few kHz to minimize in-band spurs (and then undo that shift in software with DSP). This is not an option for us as we'd need continuously variable frequency output for Varispeed operation.

This is much less of a deal with the AD9912, as (for the same DDS output frequency) even without SpurKiller and cleaner DDS processes the interval between spurs is 2.5x larger, and spur magnitude 8-9dB down just because of the higher DAC update rate.

Btw. I think iClocks have a DDS with a main clock <200Mhz in it. I think I've seen that note somewhere on their homepage.

170MHz, I believe, but that's a completely different animal. First nobody in their right mind uses an iClock to directly drive a converter chip, and besides the only jitter spec I can find for them (1ps RMS, 6ps pp) is for the TCXO driving the DDS, not for the DDS output.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 22, 2010, 10:10:25 AM
170MHz, I believe, but that's a completely different animal. First nobody in their right mind uses an iClock to directly drive a converter chip, and besides the only jitter spec I can find for them (1ps RMS, 6ps pp) is for the TCXO driving the DDS, not for the DDS output.

Yes. Different animal. The reason why I was talking about it is, I'm wondering if we really need a 1GHz-device to generate a 24.57MHz clock synchronous to a word clock.

JDB, would you say that the already mentioned AD9910 is the best device if we want to go for a TQFP package (=> best compromise)?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Svart on February 22, 2010, 10:21:42 AM
http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf

Seriously, check it out.  I2C programmable, 3x better stability than SAWs(according to the datasheet).  Programmable to any frequency from 10Mhz to 945Mhz.  You can get them in LVpecl, CMOS, LVDS and CML outputs too.

Don't know how much they cost but based on their other parts, probably a lot cheaper than the other ideas we've been discussing.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 22, 2010, 10:54:54 AM
The reason why I was talking about it is, I'm wondering if we really need a 1GHz-device to generate a 24.57MHz clock synchronous to a word clock.

If all we wanted was a 24.576MHz refclock we could even do it with a 10MHz DDS and sufficient bandpass filtering (or injection locking).

JDB, would you say that the already mentioned AD9910 is the best device if we want to go for a TQFP package (=> best compromise)?

It looks like it. Other TQFP DDSes have higher current output at 1GSps, but the 9910 would appear to have best spur performance.

http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf

Seriously, check it out.  I2C programmable, 3x better stability than SAWs(according to the datasheet).  Programmable to any frequency from 10Mhz to 945Mhz.  You can get them in LVpecl, CMOS, LVDS and CML outputs too.

I know. I mentioned it here some time ago, and some of the radio amateurs are using it. However, stability isn't very important here (can always lock to an aux TCXO), and it can't do continuous variable slewing over more than +/-0.35% which is insufficient for Varispeed.

I've said it before and I'll say it again: it might be better at this stage to either (a) support Varispeed only through a traditional tunable LC oscillator + PLL (still better jitter than mid-market equipment) or (b) not support Varispeed at all. Even with a TQFP DDS you're probably looking at a 4-layer PCB and hairy routing to get the best performance.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Twenty Log on February 22, 2010, 12:04:51 PM
I was looking at SONET / OC-3 type chips from SiLabs (DSPLL) and NSC LMK04000 series to slave to WC or internal (free run from DSPLL sample clock), but the data is not characterised for our audio purposes.. So it is frustrating to figure out response without spending the dosh on eval boards (and maybe renting some high end test gear to complement the lab here)...  Have to use your imagination (or fantasize?) about the spurs for audio sample frequency multiples when bending the output frequencies to our purposes...  Remember the A/D is a modulator that also modulates the power supply and jitter into the signal of interest...

And I remember of course the differences using the simulator for the NSC part does not support the low WC frequencies directly despite the datasheet saying it does (the simulator assumes a different mode of operation)

I haven't looked at it about a year, but the good news may be that on the DSPLL chips from SiLabs, jitter feedthrough for the DSPLL pins, XA and XB, (a.k.a the "DSP sample clock") input to the output is reduced below 12kHz...  Might not be enough though; can't remember... Everything else is near 0dB perfect feedthrough.... Maybe the clock osc/xtal I was using only had some alleged spurs below 12k, so the combination of the response of the clock and the DSPLL chip worked out on paper....

I think Multigig had something that I was planning on maybe using to pre-clean or provide reduced DSPLL clock jitter...  But it seems that they have assimilated into Micrel and I can't readily find the datasheet; most of Micrels native clock stuff is junk for our purposes...

In theory, with the simulator for NSC and the like I think I was getting near 0.8ps ~ 0.6ps of jitter... But I'm not sure I believe it....  In theory true 24-bit needs jitter somewhere near 0.4ps...

Of course, slew rate of differential clock swing can help in the additive jitter department.. but then distribution will have sharp edges and more RFI possibility and signal integrity analysis with termination would be critical...  Keeping in mind that the IBIS models for signal integrity simulation are sometimes not accurate direct from the manufacturer...

I wonder what would happen if an uber sharp PECL (converted to single ended with appropriate loading on both of the diff lines) would do to performance of the TI ADC parts mentioned in this thread when impinged upon the CMOS clock input to said chips (after proper level conversion if needed)?  

Rochey?  thoughts?  (over temperature too... would the clock section of some of the TI chips work better cold to reduce the Johnson noise perturbing the switching cross point?)

<dreaming mode>
It would be awesome if the ADC chips used true differential ECL (or better PECL) style of clock inputs and that their circuits were truly differentially clocked internally to the IC (but also able to be run single ended for consumer apps)...  (hint...) ;)

Only down side might be the need for more power supply and accoutrement near/into the chip (thicker bond wires? bond ribbon on the ol' wedge bonder?) to handle the fast and sharp current switching :(  but for consumer apps, running the proposed chip at a reduced clock swing spec might still be fine :)...

</dreaming mode>
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 22, 2010, 12:49:46 PM
I wonder what would happen if an uber sharp PECL (converted to single ended with appropriate loading on both of the diff lines) would do to performance of the TI ADC parts mentioned in this thread when impinged upon the CMOS clock input to said chips (after proper level conversion if needed)?

Meh. Given the residual jitter of even the best ~25MHz XOs (at room temperature!) ultrafast slewing doesn't help enough to be worth the effort. AC-coupling to the local switching threshold does help, or...

It would be awesome if the ADC chips used true differential ECL (or better PECL) style of clock inputs and that their circuits were truly differentially clocked internally to the IC (but also able to be run single ended for consumer apps)...  (hint...) ;)

Yeah, that's been suggested (http://www.groupdiy.com/index.php?topic=32119.msg407304#msg407304) but not likely to happen.

JD 'big customers don't care enough' B.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on February 22, 2010, 02:29:19 PM
It would be awesome if the ADC chips used true differential ECL (or better PECL) style of clock inputs and that their circuits were truly differentially clocked internally to the IC (but also able to be run single ended for consumer apps)...  (hint...) ;)

Yeah, that's been suggested (http://www.groupdiy.com/index.php?topic=32119.msg407304#msg407304) but not likely to happen.

JD 'big customers don't care enough' B.

well, one promotion later, and I'm the one that decides what goes into new performance ADC/DAC's at my employers.

I don't see differential clocking coming any time soon I'm afraid. We're already fighting to keep pincounts down (cost of die, cost of bond wire, cost of package). Add to that, the fact that most consumer systems (even the high end AVR's) don't have differential clock sources that I know of, leaves me with little I can work with. In the language of MBA folk I keep meeting (i don't have one...) -- "There isn't enough value proposition".

That's not to say it's a closed book, but the argument "for" isn't as strong as the argument "against".

I'm always open to influence though. PM me with arguments. (and keep that side of the discussion off the forum... no need to fuel the competitions' brain cells...  ;))

EDIT: I'll also add, that I have been wrong/incorrect just as many times as I've been right/correct ;)

Title: Re: Modular multi channel DIY AD/DA Box
Post by: Twenty Log on February 22, 2010, 02:56:07 PM
I hear ya Rochey... Had the same issues in R&D for 2GHz cellular handset power amps for the radio section; we had our own unique challenges for bond out and we used a Kapton lead frame bumped for BGA style.... The market was wrung out of profit margin....

But I must admit... The first transistor was not cost effective and did not have value proposition ;D (well kinda... it certainly was not practical at that time, but it was a glimmer of hope and not having to wait for the valves to warm up...  Better power supply etc...)

(http://upload.wikimedia.org/wikipedia/commons/b/bf/Replica-of-first-transistor.jpg)

Wow! look at those non-inductive bond wires!  ;D  It's not even a matched pair! hehehe

The proposed differentially clocked ADC would have to be in a different market of course and different price point (but at reduced volume yadda yadda)...  And as time goes on it would be like that first transistor changing to what it is today...

Maybe a little weak, but it's all I got until my next coffee break...  Anyone else?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: nielsk on February 22, 2010, 03:55:09 PM
My needs are for 44.1 / 48 / 88.2 / 96
I do mostly live recording, and when you have 128 inputs going over 1000 feet of fiber from the converters, through a digital console to multiple 128 track recorders and generating mixes fed to other multiple trucks for live broadcast, while resolving to the master video, Word Clock in is required.
I have yet to encounter the need to pull up/down in the field
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Twenty Log on February 22, 2010, 05:06:10 PM
Meh. Given the residual jitter of even the best ~25MHz XOs (at room temperature!) ultrafast slewing doesn't help enough to be worth the effort. AC-coupling to the local switching threshold does help, or...
...

I think I was also finding the same after some exhaustive searching this but my A/D project has been on hold for almost a year whilst waiting for some custom silicon (it also had a nice app for the TI TAS3108), so I am drawing from memory at the moment... But I found different frequencies of TCXOs and VCXOs and simulated ~25MHz using some of the SONET clock chips to have slightly better jitter; except when too many clock dividers in the LMK for example were involved to get back down to 25MHz range- so it has to be almost native in the PLL rather than some multiple near the 2nd PLL in the LMK04000 dual PLL chipies....  But again simulation... haven't built it on the bench...  It was no Wenzel in the simulation of course...  I do have a sample of an OCXO but its performance is.. eh so-so... probably the Johnson noise or something close in on the carrier...

Quote
JD 'big customers don't care enough' B.

Group_Buy == big_customers ? diff_clock : single_ended;  // Oh well.. it was a nice thought while it lasted in my brain...

Then there is the old (mildly unrelated) trick of using 2 A/Ds to sample and get an additional 3dB of performance... http://www.cirrus.com/en/pubs/appNote/AN331REV1.pdf

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 23, 2010, 03:46:43 AM
JDB, can you explain what you think what is important for selecting devices? Otherwise it will become a thread where we suggest parts and you will always say "no, because..." ;)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on February 23, 2010, 05:29:08 AM
Excellent discussion. Please continue. You guys have some great ideas here. But in my opinion, yer getting a bit carried away. But please continue anyways. I am following this closely. Once Raphael (or anyone else) starts selling PCB's, I can modify and build to suit my needs. And, as you already know, clocking is a very deep topic (of which I only know the basics). One more comment from me..... Not that many dudes use vari-speed. Yes, I imagine it's cool. In our studio, we generate all the tracks and we mix all the tracks. We don't need to do any vari-speed business. We track at 96kHz. We mix and master at 96kHz. We down-sample and dither to Red Book CD. Boom. That's it. Again, this is just my opinion. Twenty Log... You appear to be a new member here. Where you at in New Hamshire? I'm down here in Massachusetts. Thanks, DANA.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 23, 2010, 08:14:34 AM
JDB, can you explain what you think what is important for selecting devices?

For the DDS:
- low spurs and/or a way to eliminate spurs
- high DAC update rate
- high DAC output current
- easy/fast frequency updates
- clean reference multiplier, if necessary

For the limiter/squarer:
- low noise
- well-defined input impedance to properly terminate the post-DDS filter

For the divider:
- low noise
- low dynamic current (ie: minimal supply glitching when outputs change state)

The best chip for the job on the market right now is the AD9912, although the AD9910 is probably an acceptable candidate. As far as I've heard AD have a few DDSes just over the horizon (release later this year) that would be even more suitable (but again in LFCSP).

The major advantages of the AD951x squarer/dividers is that they're fast and clean, and they have easily programmable non-power-of-two dividers which makes the implementation of a post-DDS filter easier. Plus you can more easily run them at higher speeds (=lower jitter) than discrete logic.

If you were to put a gun to my head, I'd say take a 9910 into a 5 or 7-pole LC filter into either a discrete limiter or an LVPECL->TTL converter chip, into a synchronous divider like the 74LVC163. This should give you jitter performance within, say, 3dB of a VCXO.

Without a gun to my head I would still go for a microcontroller PFD plus two VCXOs, one for 44.1/88.2/176.4 operation and one for 48/96/192 operation; add an LC VFO for Varispeed if you must. Go for frequency autodetection if you want to be fancy or front panel selectors for 44.1/48/varispeed if you want to be foolproof.

JD 'easier to design, easier to build, better performance at fixed rates' B.
[plus people who only ever run 44.1 (or 48) could cheap out and only buy one VCXO]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Twenty Log on February 23, 2010, 11:20:35 AM
Hey mateys... sorry if I got a little deeper into the sea of chips choices... just on the quest for better jitter and frequency agility without spurs (maybe, hard to tell with those chips without testing them physically)..

I haven't looked at the AD clock DDS site in a while as at the time, siLabs 5326 and NSC LMK04000 were looking better with what AD had... at that time.. SpurKillers look interesting on the AD9912!  Will have to play with it...

Thanks,
-chris
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 24, 2010, 04:20:36 AM
Hey, I don't wanted to supress ideas. Ideas are always welcome. I just wanted to give it a more serious direction by having a clear 'must-fulfil'-list. :)
Thanks JDB!
The DDS approache looks interesting and I'll definitly put it on my 'projects-in-the-future'-list. But for now I think an AD9912 is not the way to go. Not only because of the package. On the internet you can find tips how to solder it at home. But I think it is simply to expensive! We are talking about 88Eur only for the chip. In my university time we always made projects with the best performing stuff but then later in my job as an engineer I learned, that you also have to keep in mind: Is there a market for it or rather are there people who want to spent that amount of money for it. And I think that there are not many DIYer who want to spent ~150Eur only for the parts for the clocking (Maybe I'm wrong). Therefore, I think now it is better to do it in the following way: First make a board with a VCXO driven clock on it providing the clocks either in master mode or locked by a PLL which is only catching fixed rates like 44.1,48,88.2,96,... and not to support varispeed (as JDB mentioned) and later to make a board with DDS on it and supporting then varispeed. But this board will be designed a little bit more complex and will be a project for advanced DIYer. But I can imagine that this board is then also able to work as a standalone master clock like iClock or Big Ben (not thinking about video sync at this moment) because then it is worth the effort and the money because you will get more features.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on February 24, 2010, 05:22:51 AM
That's it right there Raphael. A stable, low-jitter master clock which works at the common fixed rates. I believe that is a good fit for this project. We can get all fancy and DDS later (not trying to be disrespectful). Simple, reliable and stable. As we all know, some guys will be able to whack this out and some will have trouble. I can do surface-mount surgery in my sleep. I can solder TSSOP's with a fine-point iron tip. LFCSP's are a pain-in-the-ass. I would skip those. I could solder those too but what's the point. And then there's the cost you mentioned. 88Eur IC's? I'll pass on that. DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 25, 2010, 08:00:30 AM
Here is a drawing of the PLL. Please note that it is only showing the concept. Many parts are not in at this moment, like input/output and control circuits. I've tried to keep the gate count low for the clock signals but also to use widely available parts. Especially for the output select matrix we could use another part instead of the 125's. I'll have to insert a multiplexer between the VCXO and the divider to support other clock rates like 44.1 or an externally applied superclock. Depending on that the output matrix logic will be a little bit different. As soon as I know all the needed states I can probably simplify the control logic via some boolean algebra.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 25, 2010, 09:48:41 AM
Please note that it is only showing the concept.

Even so a few random notes:

- 12 bits is borderline. The usual approach is to implement a software sigma/delta-modulator and feed its output to a single/multibit DAC with a LPF after it. Keeping this differential helps in rejecting noise; you could consider a discrete DAC with a bunch of 4053-type analog switches

- turn off the power from unused VCXOs. Similarly, digital MUXes have non-infinite off-channel rejection; it helps a lot if deselected inputs are grounded (and yes I realize that that effectively implements a double MUX).

- 74AC(T) logic is notorious for producing lots of noise on supply(/ground) lines. Consider using a different family like AHC (if fast enough) or LVC.

- I'm not sure your PFD is race-free. Why not use the standard design with internal (full-speed) clock on D and external WC on CLK, with a second DFF as synchronizer? This gives effectively a phase-detector; frequency detection (and rapid capture) can be done with one of the ATMEGA's internal timers.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 25, 2010, 10:51:47 AM
- 12 bits is borderline. The usual approach is to implement a software sigma/delta-modulator and feed its output to a single/multibit DAC with a LPF after it. Keeping this differential helps in rejecting noise; you could consider a discrete DAC with a bunch of 4053-type analog switches

Well, I wanted to keep is simple. Therefore, I decided to use this parallel DAC because it is simple and cheap.

Turning off unused VCXOs is on my TODO list. You see that the enable pin is unconnected...
Yes the ACT is not the correct choice. Therefore, you see the note in the schematic regarding the HCT family. I simply used what I had in my component lib.

- I'm not sure your PFD is race-free. Why not use the standard design with internal (full-speed) clock on D and external WC on CLK, with a second DFF as synchronizer? This gives effectively a phase-detector; frequency detection (and rapid capture) can be done with one of the ATMEGA's internal timers.
I'm not sure if I understood what you mean. Perhaps you have a drawing of it? The design I used is the standard design for a PFD for both situations where f1 > f2 and f1<f2 (sign memory). The capture range is only limited by the adjust range of the VCXO and only phase offset between 0..2pi can be adjusted.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on February 25, 2010, 01:07:57 PM
- 12 bits is borderline. The usual approach is to implement a software sigma/delta-modulator and feed its output to a single/multibit DAC with a LPF after it. Keeping this differential helps in rejecting noise; you could consider a discrete DAC with a bunch of 4053-type analog switches

Well, I wanted to keep is simple. Therefore, I decided to use this parallel DAC because it is simple and cheap.

Pity it eats so many I/O pins, that makes it hard to connect multiple DACs for, say, two VCXOs and a LC VFO. I'd consider something like the MCP4922. (For extra fun, hang a low-grade audio DAC on the AVR's SPI port)

If you must use this DAC, at least include a filter at its output (referred to AGND).

Turning off unused VCXOs is on my TODO list. You see that the enable pin is unconnected...

For best noise performance the power needs to be removed from the oscillator, as the enable pin only switches the internal output buffer.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 07, 2010, 02:12:40 PM
Because I got some emails regarding the next steps of the project here is a general roadmap after the ADC group buy is done:

- GroupBuy of the DAC
- Release of the AES in/out board with/without ASRC on board
- Release of the the clocking module (currently designing)

Ideas for further modules:
- stand-alone ASRC module
- ADAT interface with ASRC on board
- helpful stuff like bar graphs etc.
- other interfaces like firewire

Any additional ideas are welcome!

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: kibadachi on March 11, 2010, 01:13:41 AM
Is there a frontpanel or case design available?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: blue_luke on March 13, 2010, 09:16:57 AM
This page is 17 pages now!!
Interesting discussion but I will have to start at page 1 and read everything I guess!!   ;D

But a short search on digikey site for the AD9912 dds shows not available and no price for it, which generaly is bad news.... then there is also an ''end of life alert''  which means there is a replacement comming soon, or a plain abandon of the product by AD  :-[

There should be a replacement solution.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 14, 2010, 12:38:17 PM
Is there a frontpanel or case design available?


Not yet. I think it would be helpful to have something like bargraphs etc. on it. The ADC/DAC board don't have a bargraph driver or something like that. Only the ADC has a clip signaling pin that can be used.
Feel free to make a frontpanel or case design. :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 14, 2010, 12:40:20 PM
I want to inform you that I've just ordered a prototype PCB for the AES output board that can be used standalone with the ADC board (no need of programming a microcontroller or something like that...).

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on March 14, 2010, 05:37:28 PM
[...] then there is also an ''end of life alert''  which means there is a replacement comming soon, or a plain abandon of the product by AD  :-[

Check again. It's the AD9912 (first revision silicon) that's on Lifetime Buy; the AD9912A is still In Production.

JDB.
[looks like ADI is transitioning from the old to the new rev right now, leading to a parts shortage. Not that it's very likely that a DIY DDS clock board will appear very soon]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: blue_luke on March 14, 2010, 07:55:38 PM
I stand corrected sir!   :D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: seavote on March 15, 2010, 11:03:46 PM
sorry for my ignorance but if im going to put the money and effort into this project i'll have to ask some newbie questions. i understand i will need some type of interface to connect this to my pc sound card. but what do in need on the input end to connect an xlr out from my preamps to the a/d converter? im sure its been discussed but can some one tell me the bitrate this a/d will give me? sample rate?  if its variable what is the range of this parameters?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on March 16, 2010, 06:16:47 AM
Good questions seavote. Try to go back and read the thread. Raphael is designing modular circuit boards. One for ADC, one for DAC, another for spdif/AES input and output and so on. The first board he is making is the ADC board. It is based on the Texas Instruments / Burr-Brown PCM4204 IC. Go to the TI website and download the datasheet. That device will do all the common audio sampling rates. 44.1, 48, 88.2, 96 and so on. The ADC board does not have a digital output section on it. That will come on one of the next boards. So you would have to home-brew the digital output circuit right now. That's what I plan to do. The PCM4204 works up to 24-bit but can most likely be put into 16-bit mode too. I would have to re-check the datasheet. And on the analog input side, Raphael's board has circuitry to take the balanced analog signals and send them directly into the ADC's. He has two opamps per channel to do this. So all you would really need to add is XLR or 1/4" connectors for that portion. I've written all of this from memory so if I have made any mistakes here, other guys will correct me. But this is pretty close to accurate. This is not a really simple project. I commend you for being interested and asking questions at the beginning. But this is a fairly complex project. One last thing.... the PCM4204 is four ADC channels in one package. So 4 analog signals can be converted. And each digital output stream consists of 2 encoded analog channels. So the board will ultimately have two digital outputs going spdif or AES or TOSLINK. But again, this ADC board only has I2S digital outputs which need to be converted to spdif or AES or TOSLINK.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on March 16, 2010, 05:34:32 PM
On way to connect this A/D to PC for an example would be to use something like TI C5515 eZdsp USB dongle kit ($79 or something, ordered mine from Digikey for 65€ inc. postage which was zero):

http://focus.ti.com/docs/toolsw/folders/print/tmdx5515ezdsp.html

This is manufactured and supported by Spectrum Digital:

http://support.spectrumdigital.com/boards/usbstk5515/reva/
http://support.spectrumdigital.com/boards/usbstk5515/reva/files/usbstk5515_TechRef_RevA.pdf

Quite a bit features for so low a price. However, Windows does not support USB Class Audio 2.0 but Apple does, guess Linux as well.  Let's hope that Microsoft soon adds support for USB Audio 2.0 to it's Windows products.

There is also the XMOS USB Audio 2 Reference Design:

https://www.xmos.com/products/development-kits/usbaudio2

You interface these boards using I2S (slave mode only with the TI kit, don't know about the XMOS). So ADAT is not the only way though I guess that's what most are waiting for.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: seavote on March 16, 2010, 06:40:56 PM
mhelein  not sure if your reply was to my post. im in a bit over my head with this project but its my understanding that the devices you referenced are used to connect the digital signal from the A/D board to a PC. cool they are great options. though i would need one for each channel of audio,no?
my post was asking how i get my audio out of a mic pre with an xlr connector into the A/D. i see no xlr audio input on the A/D converter.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on March 17, 2010, 01:59:42 AM
I am super keen to learn from this project and thank Raphael a lot for it.

Like Seavote however, I am a bit of a featherweight when it comes to this stuff and admit that I don't understand too much either.

Personally if someone was prepared to create an "RKN AD/DA for Dummies" little post or page explanation in its most basic form I would be chuffed. Even if it was something like:

1) "xlr inputs will go here",
2) "you need another card to talk the computer and the AD and DA boards and that card needs to go between here and here" etc.

Perhaps even a little diagram for extra stupid people like me.

It does beg the question that if I am this stupid perhaps I should not be embarking on such a project. In reality - and I suspect there are a few people on this board in the same boat, -  I am a little bored with my own knowledge of preamps and comps which I feel I have mastered to the level that I am happy with. Now I would love to learn something new and learning is why I am a member of this board.  This project seems like a really interesting new journey for me to embark upon and into new territory - digital electronics.  I am super keen to learn.

So with this being said, if anyone wanted to create a little post explaining this I would be so appreciative.

Kindest
Deuce
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 17, 2010, 03:15:12 AM
Perhaps I can do a basic building instruction the next days. But some remarks already here:

The XLRs can go into X102: Hot on IN+, Cold on IN-, Ground to Ground. Note: The inputs are DC coupled. Depending on your studio stuff and on your preferences it might be advisable to put either two 10u electrolytic caps or a transformer between XLR and X102.

Connectivity to a PC: That will become much easier with the AESOUT boards I've designed and I'm currently waiting for. This board has exactly the same pin layout for the I2S interface like the ADC (X103) so that you can connect them with a simple flatband ribbon cable. The AESOUT gives you 2 AES signals (=> 2 Stereo/4 Mono channels) on either  BNC connectors or on a pin header that you can connect it to any connector type you want.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on March 17, 2010, 06:03:11 AM
On page 2 of this thread is the PCM4104_module.jpg image. That is the schematic for the DAC board.

On page 10 of this thread is the DIX4192 board image and schematic. The DIX is the digital interface transceiver. A transceiver transmits and receives. That board will transmit and receive AES or spdif signals to and from a sound card. This is one way to get the digital audio into your PC and out of your PC.

Also on page 10 of this thread is the ADCmodule.pdf. That is the schematic for the ADC board. Look way over on the left hand side of that schematic. See the nodes labelled IN+:1, IN-:1, IN+:2, IN-:2......? Those are the balanced inputs. You would connect your mic pre output signal to those nodes. Balanced out from one mic pre goes to IN+:1 and IN-:1. That's one channel right there. Same for 2, 3 and 4. The PCM4204 is a four-channel device. It has four completely separate converters inside that one chip.

Go grab those three documents and save them to your PC and look at them closely. RAPHAEL reserves the right to change his designs at any time. Those drawings and schematics are preliminary and have probably changed already. But once we have etch from Raphael, I'm sure he'll provide us with updated schematics. DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 17, 2010, 08:32:09 AM
Every order of a PCB or kit will come with a schematic and a bom of the current revision.
For the ADC module we hav enow revision B with minor changes like an additional socket for master clock in.
The schematic of revision B will be published, too. I think it is good to make a website for it so that all important information are concentrated into one place. Then you don't have to read all 17 pages of this thread to get all the infos you need just to build an ADC. Unfortunately, the next few days I'll be very busy and do not have the time for doing that. So please be a little bit patient. In two weeks I'll have the time to support the DIY-building of ADCs more helpful. But maybe someone else can manage a wiki?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on March 17, 2010, 09:31:00 AM
There was some brief talk about wikis last summer. I think Kato put one up here
http://wiki.nimbleswitch.com/Main_Page

there seems to be couple entries already, not hugely popular yet :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 22, 2010, 08:17:44 AM
Good news for some of you:
The 4channel AESout PCB and the parts for the prototype have just arrived. I'm going to stuff and test this board this week so you can expect that it will be available for the DIY community with in two weeks if there are no big mistakes in the design.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on March 23, 2010, 03:38:59 PM
Mikkel states that his boards do work with SMUX.

They do, sort of.

As far as I can tell, Mikkel's OptoRec is a direct implementation of the Wavefront ADAT receiver chip. This means that while it will accept S/MUX streams (and set a flag to show the stream is S/MUX), you still need an external converter to multiplex the two 48k channels into one 96k channel. This could be implemented in a CPLD/FPGA, a fast enough microcontroller/DSP or a lot of discrete logic.

JDB.

Regarding SMUX implementation I think the easiest way would be to use Wavefront DSP-1k because they also have the software and application note for the implementation.

For the OptoRec (ADAT receiver for the DAC's) look for the AN3101-10:
 http://www.wavefrontsemi.com/UserFiles/File/AL_Info/AL31/AppNotes/WavefrontAN3101-10%20S-Mux%20Receiver%20for%20ADAT%20Optical%20Protocol.pdf (http://www.wavefrontsemi.com/UserFiles/File/AL_Info/AL31/AppNotes/WavefrontAN3101-10%20S-Mux%20Receiver%20for%20ADAT%20Optical%20Protocol.pdf)

For the OptoGen (ADAT transmitter for the ADC's) look for the appnote AN3101-09:
http://www.wavefrontsemi.com/UserFiles/File/AL_Info/AL31/AppNotes/WavefrontAN3101-09%20s-Mux%20Transmitter%20for%20ADAT%20Optical%20Protocol.pdf (http://www.wavefrontsemi.com/UserFiles/File/AL_Info/AL31/AppNotes/WavefrontAN3101-09%20s-Mux%20Transmitter%20for%20ADAT%20Optical%20Protocol.pdf)

Link to other DSP-1K appnotes:
http://www.wavefrontsemi.com/index.php?id=11,13,0,0,1,0 (http://www.wavefrontsemi.com/index.php?id=11,13,0,0,1,0)

Mikkel also happens to have a design for the OptoGen pcb (I know because I've got one such pcb from him).

Btw. Using similar approach you could combine output from 4 stereo ADC's @48k (8 mono channels) or from 2 stereo ADC's (4 channels) into single stereo channel so that you could output the data using regular S/PDIF or AES/EBU interface @192 kHz. To be able to frame the channels in ASIO (or WDM or WaveRT or ALSA or whatever) driver you had to sacrifice the audio data LSB as there is no other way to mark the beginning of the frame (in HW implementation you could use the User Data bit of course). The loss of one bit would limit the dynamics to about 6 dB*23 bits which is about 138 dB or so.

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 26, 2010, 12:34:35 PM
Update:

The AESout prototype has arrived and is stuffed now. Tommorrow I'm going to test this PCB.
This design uses the CS8406 because it can be fully hardware controlled and does not need a microcontroller like the DIX4192 used in the bigger design above.

Raphael

P.S. I mounted a the pin header because in my box I want to place the PCB a little bit away from the rear panel (I need to place several connectors on the rear panel...). But you can also mount two BNCs directly on that PCB or XLRs via the pin header.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on March 29, 2010, 03:00:52 AM
It has not been discussed in detail, but I would like to make a start:

PSU requirements for all voltages needed in this AD/DA with AES-EBU project. Even for 16 channel I/O there won't be a ridiculous amount of current draw so this certainly eases up the choices. Let's assume it'll stay well below about 1.5A for all voltages combined, which is already overkill.

If we want to make this really easy a standard selection of 78XX regulators with "application note" implementations should suffice. Moving further in complexity, a selection of LM317/LM337 with all the standard bells and whistles is a slight improvement. Still cheap and easy.

But as far as I have understood from discussions elsewhere on the web, it is exactly these stock standard PSU implementations that are holding back the performance of more serious AD/DA solutions.

Let's say we want to move into over engineering territory, and use Jung regulators or similar opamp based linear regulators. For the audio 15V rails that would certainly make an improvement. What exactly are the 5V and 3.3V rails driving? What kind of performance is expected of these supplies? Jung regulators a good idea here as well?

Oh and, what is the VBIAS voltage input for each ADC input buffer opamp?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jackies on March 29, 2010, 05:27:07 AM
In my understanding the dac chip has separate digital and audio Vcc, and I think using Jung regulator for audio Vcc is in order.
As it happens with many of my projects, I even have Jung regulator pcbs but never got around to building one to see what happens...
 ::)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on March 29, 2010, 05:59:31 AM

Let's say we want to move into over engineering territory, and use Jung regulators or similar opamp based linear regulators. For the audio 15V rails that would certainly make an improvement. What exactly are the 5V and 3.3V rails driving? What kind of performance is expected of these supplies? Jung regulators a good idea here as well?

Oh and, what is the VBIAS voltage input for each ADC input buffer opamp?

All ADC's and DAC's are mixed-signal devices. Digital data either goes in or comes out on one side. And analog signal either go in or come out on the other side. Most all digital IC's running up in the MHz region make noise. Lots of noise. The noise can come shooting out the power supply pins on these IC's (and elsewhere too). If you are contemplating building this AD/DA modular project, I suggest you go download a couple of datasheets. Go download PCM4204 and PCM4104 at TI.com. The digital side of these devices needs regulated +3.3vdc. The analog side needs +5vdc. I am sure that various people will debate the requirements for the digital supplies. Low-impedance, low-noise supplies with proper decoupling caps right at the converters. And the analog side is either creating your analog output signal. Or feeding it into the ADC's for conversion. Jung regulators here are not going to hurt at all. In fact, I'm sure they will help........... And then to address the last question........... VBIAS is a reference voltage usually created by the ADC IC itself. VBIAS is set at one-half of the total input voltage range. Even though analog audio can sometimes go to pretty high voltage levels, the ADC's can only accept an input signal between 0 and 5 volts. So VBIAS is +2.5v and the signal fed into the ADC inputs are centered at +2.5 and can swing from 0 to 5v without causing any digital over's. DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on March 29, 2010, 06:41:08 AM
Even though analog audio can sometimes go to pretty high voltage levels, the ADC's can only accept an input signal between 0 and 5 volts. So VBIAS is +2.5v and the signal fed into the ADC inputs are centered at +2.5 and can swing from 0 to 5v without causing any digital over's. DW.

Full scale input voltage for PCM4202 is 6.0 VPP.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on March 29, 2010, 07:03:42 AM
Even though analog audio can sometimes go to pretty high voltage levels, the ADC's can only accept an input signal between 0 and 5 volts. So VBIAS is +2.5v and the signal fed into the ADC inputs are centered at +2.5 and can swing from 0 to 5v without causing any digital over's. DW.

Full scale input voltage for PCM4202 is 6.0 VPP.

6Vpp differential.

For a differential signal with a common-mode voltage of 2.5V, each of the input pins must stay between 1V and 4V to avoid clipping, and between -0.3V and 5.3V to avoid damage to the chip.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on March 29, 2010, 07:56:50 AM

But as far as I have understood from discussions elsewhere on the web, it is exactly these stock standard PSU implementations that are holding back the performance of more serious AD/DA solutions.



This is exactly what I have read many a time as well. It's poor power supply designs in prosumer commercial units that hampers the converter box and affects things like its headroom.  
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on March 29, 2010, 08:07:33 AM
This is exactly what I have read many a time as well. It's poor power supply designs in prosumer commercial units that hampers the converter box and affects things like its headroom.  

Not headroom. That is probably never the case. AD/DA units are always "low current" and regulators simply won't sag. If they did, your digital chips would simply refuse to work.

Rail noise is the real issue here. From noisy regulator outputs, or noise coupled between IC's that should never "see" each other through rails.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 29, 2010, 08:13:57 AM

Full scale input voltage for PCM4202 is 6.0 VPP.

6Vpp differential.

For a differential signal with a common-mode voltage of 2.5V, each of the input pins must stay between 1V and 4V to avoid clipping, and between -0.3V and 5.3V to avoid damage to the chip.

JDB.
[/quote]

And that's why you have a input divider option on the ADC board. :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on April 03, 2010, 11:57:07 AM
Hi,

I'm happy to tell you that the AESout board passed the test in the prototype. So we can now add AES out to the feature list!

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on April 03, 2010, 12:41:11 PM
Here I started the group buy of the AES out boards:

http://www.groupdiy.com/index.php?topic=38556.0

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Johndcx on April 03, 2010, 07:40:20 PM
This a great build idea , but is there a way to use DOa s on IN's and outs?
It seems that is where all the conveters fall short,I know that is what Burl audio is doing..
Keep up the good work.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on April 03, 2010, 09:26:04 PM
Ok I am going to ask a very dumb question(s) now so apologies in advance.

These AES boards:

1) They have four channels just like the A/D boards do. So if you have ordered two A/D boards, you accordingly need two AES boards as well to make 8 channels?

2) These boards represent the input side of this project? So XLRS etc connected to these boards are your audio signal inputs?

3) I want to eventually connect this AD and DA project via lightpipe so I can use an M Audio lProfire lightbridge as a pro tools dongle. My idea is to use a good quality converter like this project, but the inputs and outputs of this project will be lightpipe connected to the ins and outs of the M Audio lightbridge.   Do these AES boards connect via lighpipe rather than XLR etc?

Once again apologies if this stuff is pretty obvious
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on April 06, 2010, 04:24:01 AM
Ok I am going to ask a very dumb question(s) now so apologies in advance.

These AES boards:

1) They have four channels just like the A/D boards do. So if you have ordered two A/D boards, you accordingly need two AES boards as well to make 8 channels?

2) These boards represent the input side of this project? So XLRS etc connected to these boards are your audio signal inputs?

3) I want to eventually connect this AD and DA project via lightpipe so I can use an M Audio Profire lightbridge as a pro tools dongle. My idea is to use a good quality converter like this project, but the inputs and outputs of this project will be lightpipe connected to the ins and outs of the M Audio lightbridge.   Do these AES boards connect via lighpipe rather than XLR etc?

Once again apologies if this stuff is pretty obvious
1. Not quite. "It can be directly connected to the AD board and accepts two I2S input streams and puts out two AES output streams. That gives in total 4 mono channels." Each AES digital signal is two encoded analog audio channels. Raphael's ADC board has two PCM4204 devices on it. Each PCM4204 is 4 ADC input channels. So two of those is 8 analog audio channels. Eight analog channels going into 2 PCM4204's will produce 4 I2S digital output signals from those 2 PCM4204's. So if you have ordered two A/D boards, you need 4 AES boards.

2. Incorrect. The signals coming off the AES boards are your digital outputs. You can use XLR's there to transmit the digital signal if you decide to do balanced AES instead of unbalanced SPDIF. I do AES. But those XLR's are transmitting a digital signal and not receiving an analog signal. Your analog signal inputs will be elsewhere.

3. Yes and no. Mostly no. You can take any one of the AES output signals and transmit it via TOSLINK optical. But that will be one AES signal transmitting 2 encoded analog audio channels. That's optical SPDIF and not ADAT. ADAT is basically multiplexed optical SPDIF. Eight analog signals are digitized and all jammed into one ADAT stream (with sample rate up to 48kHz). I do not know the Lightbridge that well but I'm guessing it wants to receive ADAT signals and not multiple optical SPDIF signals. Most boxes don't support more than one optical SPDIF input. They could do that but the manufacturers are lazy and cheap and rarely implement that. In order to receive the I2S output signals from the ADC board and convert it to ADAT, you need another board which Raphael is not going to produce (not yet anyways). Someone else makes one of those. I think his name is Mikkel and he's mentioned much earlier in this thread.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on April 06, 2010, 04:37:04 AM
ad 1)
Tubemooley, you are not right, deuce42 is right. Have a look on the schematic:
On every AD board is only 1 ADC taking four analog inputs and putting out 2 I2S channels.
The number of ADC boards and AES boards must be identical.
Some example configurations are:
1 ADC boards => 1 AES board
2 ADC boards => 2 AES boards
3 ADC boards => 3 AES boards
...

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on April 06, 2010, 09:21:11 AM
Ah.... Very good. Sorry for the mix-up. Not sure where I got that two ADC per board thing. DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ognam2 on April 22, 2010, 03:48:52 AM
Very interesting Project!
Are there already finishes units? Maybe some Pictures?
Which boards to I need to do A 8x ADAT AD/DA Box, and where can I get them?

Thanx Jonas

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on April 22, 2010, 04:10:42 AM
Very interesting Project!
Are there already finishes units? Maybe some Pictures?
Which boards to I need to do A 8x ADAT AD/DA Box, and where can I get them?

Thanx Jonas

I suggest you read the thread from top to bottom.  All your questions are answered and you would do well to get totally up to speed on what's going on here. 

I don't want to be dismissive but it's a complicated project with a lot of potential variables.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on April 28, 2010, 06:09:34 AM
I am slowly working on a way to interface these to the computer via a cheap and simple ethernet cable

Hey baadc0de,

Just wondering if you had made any further progress on this interface?  You seemed to really be going full steam ahead for a while.

Any news?!

Cheers,

Rob  :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on April 30, 2010, 05:11:46 AM
Well, Rob, the devil is in the details. Developing such an interfacing is easily a commercial grade project. As far as I know he worked on the ASIO part of a driver and managed to transport raw audio over LAN interface between computers...
Me myself started a KS/WDM pc driver and managed to get a 24bit/96khz configurable dummy driver working up to the interface of a network device driver where i got stuck and hold on to make myself clear about the converters side of things....
Title: Re: Modular multi channel DIY AD/DA Box
Post by: joe333 on May 05, 2010, 02:22:15 AM
Hi

This thread looks ended!!
Somebody has build the AD/DA with success?
Opinions about how it sounds compared with commercial ones?

thanks
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 05, 2010, 02:40:16 AM
No it is not ended. :D

Currently we are waiting for the AD chips and then many members of this forum will start to build ADCs I think. The group order of AES output for the ADC is done andthe PCBs are in production. The group buy of the DACs will come next. And I know there are other developments running in the background.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on May 05, 2010, 04:14:13 AM
Well, Rob, the devil is in the details. Developing such an interfacing is easily a commercial grade project. As far as I know he worked on the ASIO part of a driver and managed to transport raw audio over LAN interface between computers...
Me myself started a KS/WDM pc driver and managed to get a 24bit/96khz configurable dummy driver working up to the interface of a network device driver where i got stuck and hold on to make myself clear about the converters side of things....

Ah excellent - glad to see this thread getting some updates.

Thanks for your input too s-b-f - I forgot to reply to your reply the other week ;)

Cheers,

Rob
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on May 05, 2010, 05:55:44 AM
I hate to be a snot...... But I already have my PCM4204's. I had them before I had the etch from Raphael. Come on guys.... Let's get with it. As soon as my lithium kicks in, I'll sit down and solder those TQFP-64 bad boys. Oh mama........... DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: SIXTYNINER on May 05, 2010, 01:14:43 PM
bump

Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on May 05, 2010, 02:55:18 PM
bump

...why?

The last post to this thread was less than eight hours before yours; the last post by the thread-starter/designer less than eleven.

As far as I can tell this was your first post to this thread. Do you have a specific question which was not yet answered?

JD 'IDGI' B.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on May 06, 2010, 02:54:43 AM
Is it OK to use CAT-5e cable for connecting the AD/DA modules using I2S directly to a PCI soundcard (using some transmitter/receiver chips and transformers)? Some folks use the ESI [email protected] soundcard (http://www.thomann.de/gb/esi_juliat.htm ) for connecting DIY DAC's via I2S (which is only meant to be used "inter IC", not directly as interconnect between devices). This soundcard has two boards, the other has the PCI controller (Envy24HT), and the other the converters and is detachable, so you only had to design a digital board (I2S or AES could also be possible) which replaces the analog board. The soundcard is quite an inexpensive one though it also supports chaining of multiple cards, but I'm not sure about it's jitter performance in such case.  Well, another thing is that CAT-5 cable only has twisted pairs so we would have to use two cables for 8 channels in and 2 out. [email protected]'s analog board is only a 2 in 2 out though, not sure if all of the Envy24 HT inputs and outputs are exposed on header (guess not, and the driver doesn't support them either, but VIA general driver might be able to do that).

Easy I2S from [email protected]: http://www.head-fi.org/forum/thread/242285/easy-i2s-from-juli-pci-sound-card

Seems the folks there doesn't much know what they are doing. The signals on scope (some pics posted in the thread) look just awful (lots of ringing and everything else).

Title: Re: Modular multi channel DIY AD/DA Box
Post by: Tubemooley on May 06, 2010, 04:28:10 AM
This is a difficult question. Some people say yes it will work. Others say no it will not work. Looking at SPDIF/AES signals on a scope is borderline nightmare. They're pretty messy. You have to be able to see the good stuff among all the noise and ringing. It's not that easy. AES/EBU is a modified form of RS-422. It is a very specific protocol specified by the AES society. When implemented the way it's spec'd, it works. When implemented another way...... well.... ya' never know. I have read about guys who transmit AES over Cat-5 and it worked for them. Now concerning I2S...... I think you're even further out on a limb doing that. I2S is not designed to go long distances. Maybe inches. Not feet or meters. Sketchy at best. DW.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on May 06, 2010, 05:11:56 AM
Is it OK to use CAT-5e cable for connecting the AD/DA modules using I2S directly to a PCI soundcard

Not enough information.

As Tubemooley indicates, length is an issue. A few inches will probably work fine, an entire 100m-reel probably won't. Adding series termination resistors (as mentioned in the thread you linked to) will help. Signal rise-time is a factor, probably not documented for the [email protected] Grounding/ground loops can get in the way. This approach will likely not be too great from a jitter POV.

On the other hand, CAT-5 is cheap, and you can just try it and see if you like the results. Do add a series resistor in each signal line at the driving ([email protected]) end. Only drive one wire of each twisted pair, connect the other to ground at the [email protected] interface connector. Use the shortest run you can get away with. See if you like it.

(Those scope shots do look ringey, but that may have as much to do with probing technique as with anything else. Properly scoping fast signals is non-trivial).

(using some transmitter/receiver chips and transformers)?

Well, yes, maybe. I was going to write suggestions about using LVDS transmitters/receivers on all of the signals and driving CAT-5 or ribbon cable with them, but at that level of complexity you may as well add a few S/PDIF transmitters on the [email protected] end.

JDB.
[one obvious way to improve jitter performance would be to move the audio clock to the converter end of the cable, as is popular in the CD/DAC-modding crowd. This can get impractical if the clock is synthesized inside the [email protected]'s digital chipset]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: joe333 on May 06, 2010, 07:37:19 AM
Dynaudio, Tannoy and tc electronics are not using dig audio over cat5 cable in their surround systems?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on May 06, 2010, 08:45:19 AM
Dynaudio, Tannoy and tc electronics are not using dig audio over cat5 cable in their surround systems?

Apples and oranges.

The question "is there a way to run digital audio over cat5" doesn't necessarily have the same answer as "Is it OK to use CAT-5e cable for connecting the AD/DA modules using I2S directly to a PCI soundcard".

JD 'horses for courses' B.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on May 06, 2010, 11:38:26 AM
Hey Guys,

Quick NOOB question, as i've never worked with ADC before.

I want to buy some I2S to ADAT boards. So when wiring these boards, do we tie two of the outputs of the ADC boards in parallel? That is, is there just one main I2S bus that we use? Or will an I2S to ADAT board have multiple inputs for I2S?

Does that make sense? I am asking because i want to know how many I2S to adat boards i need for 4 of these boards (16 channels).

Thanks.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on May 06, 2010, 01:32:47 PM
I want to buy some I2S to ADAT boards. So when wiring these boards, do we tie two of the outputs of the ADC boards in parallel? That is, is there just one main I2S bus that we use? Or will an I2S to ADAT board have multiple inputs for I2S?

Could be implemented either way, but simple boards with the Wavefront chip will likely have multiple I2S inputs.

I am asking because i want to know how many I2S to adat boards i need for 4 of these boards (16 channels).

Depends on the board, and if you want/need support for double/quad speed (96k/192k).

JDB.
[note that the only ADAT boards I've seen so far are Mikkel's OptoRec/OptoGen (http://electronics.dantimax.dk/Kits/Digital_audio/index.html), and at first glance they dont' support anything other than 44k1/48k without external multiplexing]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on May 06, 2010, 01:34:51 PM
I am slowly working on a way to interface these to the computer via a cheap and simple ethernet cable

Hey baadc0de,

Just wondering if you had made any further progress on this interface?  You seemed to really be going full steam ahead for a while.

Any news?!

Cheers,

Rob  :)

Hi Rob (and everyone else!)

Yes, I've been working on an ASIO driver using libpcap and FPGA sw/hw that would integrate with rkn80's A/Ds and D/As. I've hesitated about maybe opening another thread for this, but since there's not much to write about, I hope it's appropriate to update you all on the current status here:

sw/driver:
-- can transmit/receive audio using raw audio over ethernet between computers. It has its bugs, but as a proof of concept it works well enough (reliably)
-- This isn't using i2s, it's a simple custom protocol, though I might end up buying specs for AES51, AES47 and AES3 and implement those
-- it works only with ASIO hosts for now, and I have a hard time deciding if I want to go WDM/KS/WaveRT or keep it ASIO only. Don't ask about Mac/Linux yet, please, I'd like to make it work on a WinPC

hw/fpga:
-- i haven't decided on a FPGA to use for this project yet and am unsure how exactly to design an interface "card" that would host it. Help would be duly appreciated.
-- I'm looking at http://www.farnell.com/datasheets/33325.pdf currently, the FPGA itself is cheap enough as is this board
-- I'm looking for a gigabit PHY/MAC to go with this FPGA, integrating it might be painful. There's an opencore that I could use for aid, however: http://opencores.org/project,ethernet_tri_mode
-- something like a 300Mhz core might be able to pull off 64 channels at 96k/24-bit

The general theory is for the FPGA interface card to reside in a box together with the D/A, A/D cards and whatever clocking arrangement you would have and provide you with a gigabit ethernet port that you can connect to a switch or directly to a PC. You would configure the driver with a configuration tool (number of channels, sample rates, ethernet port you connected to, MAC address) and then "It Should Work" with your favourite multitrack recording software :)

If I decide to go the WDM/KS route, it would work with regular applications and games, too.

EDIT: about the (short/long)hand future tasks:

-- make sure the FPGA development board is a good enough one to develop and test on, then buy it
-- select a MAC/PHY chip and design/buy eval circuitry that will get FPGA data to the PC
-- verify that the FPGA<->PC roundtrip works via ethernet MAC/PHY
-- work on the FPGA sw to support a fixed, 2ch input board
-- build and test the A/D input board with FPGA hw
-- connect these and verify that 2ch of audio can be extracted from the A/D [milestone]
-- work on the FPGA sw to support output cards (D/A) and multiple inputs/outputs
-- design the real interface card with the FPGA and MAC/PHY on it
-- ... other nice features
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on May 06, 2010, 01:48:33 PM
-- i haven't decided on a FPGA to use for this project yet and am unsure how exactly to design an interface "card" that would host it. Help would be duly appreciated.

Have any specific questions? I generally use the Xilinx stuff at work, and several of the Digilent eval boards are cheap and powerful enough.

-- I'm looking for a gigabit PHY/MAC to go with this FPGA, integrating it might be painful. There's an opencore that I could use for aid, however: http://opencores.org/project,ethernet_tri_mode

The folks at Ettus Research (http://www.ettus.com/) tried to use that one for their USRP2 software defined radio platform and found it was broken in so many ways that they were forced to abandon it and write their own.

I'd suggest sticking to 100TX, as that is nearly universally compatible and 'light' enough to consider implementation on a fast (ARM) microcontroller instead of (/in addition to) an FPGA. Three dozen channels at 24/96 should be enough for a start, no?

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on May 06, 2010, 03:18:21 PM

Hi Rob (and everyone else!)

Yes, I've been working on an ASIO driver using libpcap and FPGA sw/hw that would integrate with rkn80's A/Ds and D/As. I've hesitated about maybe opening another thread for this, but since there's not much to write about, I hope it's appropriate to update you all on the current status here:

sw/driver:
-- can transmit/receive audio using raw audio over ethernet between computers. It has its bugs, but as a proof of concept it works well enough (reliably)
-- This isn't using i2s, it's a simple custom protocol, though I might end up buying specs for AES51, AES47 and AES3 and implement those
-- it works only with ASIO hosts for now, and I have a hard time deciding if I want to go WDM/KS/WaveRT or keep it ASIO only. Don't ask about Mac/Linux yet, please, I'd like to make it work on a WinPC

hw/fpga:
-- i haven't decided on a FPGA to use for this project yet and am unsure how exactly to design an interface "card" that would host it. Help would be duly appreciated.
-- I'm looking at http://www.farnell.com/datasheets/33325.pdf currently, the FPGA itself is cheap enough as is this board
-- I'm looking for a gigabit PHY/MAC to go with this FPGA, integrating it might be painful. There's an opencore that I could use for aid, however: http://opencores.org/project,ethernet_tri_mode
-- something like a 300Mhz core might be able to pull off 64 channels at 96k/24-bit

The general theory is for the FPGA interface card to reside in a box together with the D/A, A/D cards and whatever clocking arrangement you would have and provide you with a gigabit ethernet port that you can connect to a switch or directly to a PC. You would configure the driver with a configuration tool (number of channels, sample rates, ethernet port you connected to, MAC address) and then "It Should Work" with your favourite multitrack recording software :)

If I decide to go the WDM/KS route, it would work with regular applications and games, too.

EDIT: about the (short/long)hand future tasks:

-- make sure the FPGA development board is a good enough one to develop and test on, then buy it
-- select a MAC/PHY chip and design/buy eval circuitry that will get FPGA data to the PC
-- verify that the FPGA<->PC roundtrip works via ethernet MAC/PHY
-- work on the FPGA sw to support a fixed, 2ch input board
-- build and test the A/D input board with FPGA hw
-- connect these and verify that 2ch of audio can be extracted from the A/D [milestone]
-- work on the FPGA sw to support output cards (D/A) and multiple inputs/outputs
-- design the real interface card with the FPGA and MAC/PHY on it
-- ... other nice features

Wow

Wow

Wow!

What incredible work. 

I am so excited about this.  What a perfect partner to the boards that Raphael is supplying - true DIY spirit.

I am sorry that I can't offer any technical help - this is so beyond my level
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on May 06, 2010, 05:03:14 PM
Have any specific questions? I generally use the Xilinx stuff at work, and several of the Digilent eval boards are cheap and powerful enough.

-- snip --

I'd suggest sticking to 100TX, as that is nearly universally compatible and 'light' enough to consider implementation on a fast (ARM) microcontroller instead of (/in addition to) an FPGA. Three dozen channels at 24/96 should be enough for a start, no?

JDB.

I'm looking for a FPGA core that is cheap, easy to obtain in the US and EU, is DIY solder-able (no funky BGA packaging), available as an eval/devel board with 100Mbit Ethernet in an arrangement that would be easy to copy to our interface board and has a high enough clock to push 32 bidirectional 96k/24-bit channels to Ethernet (though the reality of 100tx being able to handle this data transfer rate uncompressed is questionable). EDIT: and the eval board should have enough pins available to actually test bi-directional 24-ch i2s operation.

Possibly this one? (http://uk.farnell.com/xilinx/hw-spar3e-sk-uk-g/kit-starter-spartan-3e/dp/1605826?Ntt=digilent+Spartan+3E+Starter+Board)


We had a discussion with rkn80 about how many channels it would be cool to push.. there was an idea of supporting up to almost 200.. that's hard even for gigabit to handle reliably as a developer from a next-door firm tells me they have a hard time getting 500mbits out of a gigabit chip. I'm happy to keep it 100tx, though that might limit people to 24ch in/out until the driver would get multihead.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: volker on May 07, 2010, 05:33:14 AM
Spartan3 looks like a reasonable choice for price and availability (can't say too much about it's capabilities yet :D), and it's available in QFP packages.
Just recently I was also looking into getting a development board, maybe you want to take a look here (http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,400&Cat=10) as well.
There are also several with on board ethernet, though the ones with gigabit are a bit more pricey. Good discounts for students ;).
Still an ARM or something similar is probably simpler to implement for an actual working unit, as JDB pointed out. They also come with hardware integrated ethernet.


For me something like 32-48 channels out would be totally enough, in maybe something like 24 max. ASIO only would be fine for me as well.


I'm really excited about your progress! Be sure to keep us posted.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on May 07, 2010, 08:24:52 AM
I'm looking for a FPGA core that is cheap, easy to obtain in the US and EU, is DIY solder-able (no funky BGA packaging), available as an eval/devel board with 100Mbit Ethernet in an arrangement that would be easy to copy to our interface board and has a high enough clock to push 32 bidirectional 96k/24-bit channels to Ethernet (though the reality of 100tx being able to handle this data transfer rate uncompressed is questionable).

While several smaller FPGAs are available in QFP, I wouldn't consider those DIY solderable, at least not for the average DIYer. There's also the question how cost/time-effective it is to spin a multi-layer PCB just for this project. I would suggest looking at an existing FPGA board, preferably with Ethernet connectivity, and using that as the core for the digital transmitter.

Possibly this one? (http://uk.farnell.com/xilinx/hw-spar3e-sk-uk-g/kit-starter-spartan-3e/dp/1605826?Ntt=digilent+Spartan+3E+Starter+Board)

Looks workable, but it might be cheaper to order them directly from Digilent.

As for channel count: it's a bit hackish, but you could always have each FPGA board handle up to 32 channels to/from 100B-TX and connecting these to ports on a 100/1000-switch (or multiple PCIe boards) if you need more channels.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 07, 2010, 08:37:47 AM
Just an idea:

What about using a Blackfin DSP for it? Some of the evaluation boards are cheap and come with a 10/100 Ethernet. Most of the basic software like TCP/IP stack etc. is available, I2S is already there, you can program it in C and you get some DSP power.
I've seen DIY boards with Blackfins on it already in the OpenHardware group.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on May 07, 2010, 08:46:03 AM
What about using a Blackfin DSP for it?

Not a bad idea at all. I've done some work with those, and the software tools are fairly mature these days.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 13, 2010, 08:01:27 AM
An update: I've just finished the design of an simpler AES input board that can be used together with the DAC modules and does not need a microcontroller to be programmed.
This module offers 2 stereo / 4 mono AES inputs and the same I2S connector layout like on the other boards. Next week I'll order a prototype of it and as soon as the module is working I'll start the group buy for the DAcs and this module.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on May 14, 2010, 01:51:23 AM
Spartan3 looks like a reasonable choice for price and availability (can't say too much about it's capabilities yet :D), and it's available in QFP packages.

i'd avoid the original Spartan 3 series. Actually, I'd avoid all but the Spartan 3AN parts and here's why:
a) onboard config EEPROM (which looks like an SPI part and is big enough to be used for more than just config data),
b) requires only two supplies, +1.2V for core and +3.3V for the I/O (unless you need a +2.5V or other rail).

Having said that, S3E has more package options. S3AN50 is the only flavor in a non-BGA package.

The S3A/AN starter kit has an Ethernet PHY and connector. Do the MAC in the FPGA, which is the 700 part.

Oh, do you need 5V I/O capability? That limits options to the older families.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Minotaurus on May 18, 2010, 08:08:02 PM
Hi there,

I am new to the board and new to DIY Audio Stuff. I really think this Project rocks, but i guess i will wait a little until i will give it a try. i think i will start with the SSL Compressor clone or something. Is there a SVN (Sourceforge or whatever) and maybe a WIKI for the drivers yet? Or is baadc0de doing all the work by himself?  If help is needed, I would be happy to help. If a svn server or a wiki is needed, i could set them up easily on a free webspace somewhere. If there is work with the actual programming of the drivers, i think i could help as well. i know C. C++, C# and Assembler but i dont have much experience with ic programming yet, but i am looking into it.

Best Regards,

Klaus
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on May 19, 2010, 05:45:21 AM
Hi there,

I am new to the board and new to DIY Audio Stuff. I really think this Project rocks, but i guess i will wait a little until i will give it a try. i think i will start with the SSL Compressor clone or something. Is there a SVN (Sourceforge or whatever) and maybe a WIKI for the drivers yet? Or is baadc0de doing all the work by himself?  If help is needed, I would be happy to help. If a svn server or a wiki is needed, i could set them up easily on a free webspace somewhere. If there is work with the actual programming of the drivers, i think i could help as well. i know C. C++, C# and Assembler but i dont have much experience with ic programming yet, but i am looking into it.

Best Regards,

Klaus


Hi. The drivers are being written in C(++), by me alone, currently targeting windows only. I am currently wrestling with WDF to get best of both worlds (faster access to ethernet and still remain a userspace driver). I'm not ready to release source code or commit to a multi-developer setup yet, however, once the hardware to support has been selected/built and tested [AD boards, DA boards, IF board], I will open the drivers and have other people, if not anything else, check the driver for errors and spot possible improvements.

Spartan3 looks like a reasonable choice for price and availability (can't say too much about it's capabilities yet :D), and it's available in QFP packages.

i'd avoid the original Spartan 3 series. Actually, I'd avoid all but the Spartan 3AN parts and here's why:
a) onboard config EEPROM (which looks like an SPI part and is big enough to be used for more than just config data),
b) requires only two supplies, +1.2V for core and +3.3V for the I/O (unless you need a +2.5V or other rail).

Having said that, S3E has more package options. S3AN50 is the only flavor in a non-BGA package.

The S3A/AN starter kit has an Ethernet PHY and connector. Do the MAC in the FPGA, which is the 700 part.

Oh, do you need 5V I/O capability? That limits options to the older families.

-a

I/O is required to be a multitude of TTL pins. And ofcourse, some kind of ethernet, the faster the better :) So you would suggest the S3AN50?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on May 20, 2010, 12:12:33 AM
I/O is required to be a multitude of TTL pins. And ofcourse, some kind of ethernet, the faster the better :) So you would suggest the S3AN50?

As long as the inputs don't have to deal with 5V TTL (3.3V LVTTL works well) then all's well with the S3AN parts.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 31, 2010, 09:57:31 AM
I opened a new thread focussing on building the ADC of this project. You can find it here:
http://www.groupdiy.com/index.php?topic=39392.0 (http://www.groupdiy.com/index.php?topic=39392.0)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: smallbutfine on June 01, 2010, 12:50:41 PM
@baadc0de:
It's  been a long while since I wrote about my experiments to develop a WDM driver to send audio to ethernet.
I looked into the code again and re-built the driver i had from the DDK.
As of to my knowledge, the best template for a driver we would need are the msvad samples.
I managed to get the WINDDK 7600.16385.0 sample driver vadpcmex.sys working without crashing at all now and after a few tweaks it shows up it's interface correctly to Sonar with Kernel Streaming WDM, to DirectX, whatever... with up to 8 channels (for now) up to 96khz/24bit. It is only capable to stream the audio to a wave file on disk as long as i reduce to 2 channels (harddriver performance reasons...), so I am not sure about the realtime capability for ethernet device, but pretty optimistic.
As far as I know there are no 'known working' examples of such a kind of driver for Win7 right now, but to my knowledge msvad is working up to Vista at least, and there you will have to deal with WDM anyway....Why wouldn't be a kernel mode driver be preferable?  ???

Kind regards,
Martin
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rolo95 on June 02, 2010, 03:24:16 PM
Audio over ethernet is something like what this guys do ?

http://www.networksound.com/Digsnake.html
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on June 13, 2010, 10:00:38 AM

My first SMD!

(http://www.robgould.plus.com/SMD.JPG)

It sure ain't neat, but it works!

To all the people who aren't sure if they're capable of this (I included myself in this category until I tried), just dive in and give it a go.  It'll take some practise to get it looking as neat as my through hole work, but I've checked out the work in the photo with a multimeter, and it measures as it should.

The brown marks you can see on the photo are where I have added flux before soldering.  This does seem to make the components 'take' to the board more easily, but it doesn't look very nice.  Is there any problem except cosmetics with leaving it there?

Title: Re: Modular multi channel DIY AD/DA Box
Post by: Igor on June 14, 2010, 08:09:33 PM
You can always clean the flux residue with isopropilene alcohol or special solvent.
Good flux, don't afraid to put more, that's all. 0204 smd's are also solderable:)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on July 05, 2010, 06:36:34 AM
It has been a bit quiet on this front lately. What has everybody been doing? I'm currently one AES-EBU cable (to RME HDSP) short of starting testing the input cards I have. I built a PSU based on some super regulators, even for the 3.3V line.

rkn80, What's happening with the output part of this project? Are there going to be PCB available?

And how should clocking be set up with the between input and output using your AES-EBU PCB's?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on July 08, 2010, 10:25:25 AM
Perhaps everybody is soldering?  ::)

Seriously I've been away for some days and currently I'm processing and shipping the last orders for AES outputs. I'm planning to start the DAC PCBs order phase next week but I'm not sure if that is a good idea due to holiday time.  ???

Regarding clocking I'll write something in the build help thread.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: JoelC on July 11, 2010, 06:35:14 PM
Curious - how much would the total cost be?

Say if it's a unit similar to the SSL Alpha Link with 24ins / 24outs.

Been following this post for awhile now...  excited/impatient/skeptical/curious/optimistic ... :D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: truzz on August 02, 2010, 11:43:26 AM
Curious to know if there is further development ......
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on August 02, 2010, 02:59:29 PM
Well,... i kept putting it off in favor of other things, until now job & family & studio mainly dominate my time. I don't feel like I can pursue this much further, so I'm selling my A/D kits (at a discount, ofcourse)..

There is much potential in this project (especially with AES in/out boards and similar) and I hope somebody picks up the idea of an ethernet controller.. When pressed for inputs for larger sessions, i simply had to buy an alphalink system :-[ and the incentive is pretty much gone..
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on August 09, 2010, 04:51:16 AM
I'm sorry. Currently there is no further development because managing the group buy eats a lot of free time and some members seem not to care about their order and that I already paid for them.  >:(
Title: Re: Modular multi channel DIY AD/DA Box
Post by: zayance on August 09, 2010, 05:55:36 AM
Sad to hear about that  :(, of course this project doesn't seem to be one of the easiest for most people, so maybe that's why they all back up, personnaly, i'll be making your project, and will have a lot of fun i'm sure, maybe even grab a second PCB for having 8 channels, too bad their will be no more development on this, some nice features like USB or Firewire would have been great, but i'm sure there is a way around that, still not into it right now to found out the way to do it...

PS: BTW how many PCB are left in you hands?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on August 09, 2010, 06:15:04 AM
I'm sorry. Currently there is no further development because managing the group buy eats a lot of free time and some members seem not to care about their order and that I already paid for them.  >:(

Oh crap! I was already looking into configuring this project further with arduino. My first 4 channel input module, AES board and its PSU's are working fine.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on August 09, 2010, 06:24:23 AM
Oh sorry, I think there is a misunderstanding. Definitely I'll continue with new modules etc. because I need/want them. I just want to say that the progress will be slower due to a lake of time.

Raphael

P.S. I have ~20 PCBs left.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: zayance on August 09, 2010, 06:45:10 AM
Cool, wow 20 PCB's,i understand why you're pissed off, but i think the more this project continues the more people will be interested, of course it's performance will play a game also, but anyway, thanks for pursuing...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on August 09, 2010, 06:36:55 PM
hoping to get back to this project soon myself.  sorting out power, clocking and maybe limiting in front of 32 channels is a bit over my head at the moment!  suggestions welcome  ;)

Oh crap! I was already looking into configuring this project further with arduino. My first 4 channel input module, AES board and its PSU's are working fine.
how would you compare them to converters you've used previously?  i'll be using them either way, but i'm curious to hear preliminary opinions.

I'm sorry. Currently there is no further development because managing the group buy eats a lot of free time and some members seem not to care about their order and that I already paid for them.  >:(
unfortunate to hear raphael.  hopefully once a few more of us get ours up and running there will be more incentive for others to scoop up the rest of them.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on August 09, 2010, 07:28:02 PM
how would you compare them to converters you've used previously?  i'll be using them either way, but i'm curious to hear preliminary opinions.

I'm not that far yet. Sound is passing through, measurements come out ok and nothing is terribly out of spec.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on August 19, 2010, 08:19:07 AM
Hi,

I've opened ordering threads for the DAC boards and the AESin boards. You can find these threads here:
http://www.groupdiy.com/index.php?topic=40527.0 (http://www.groupdiy.com/index.php?topic=40527.0)
http://www.groupdiy.com/index.php?topic=40528.0 (http://www.groupdiy.com/index.php?topic=40528.0)

Raphael

Title: Re: Modular multi channel DIY AD/DA Box
Post by: jackies on August 19, 2010, 08:30:22 AM
Hi Raphael, great to see you making progress with this!
So you won't be offering DAC/AES in as a kit?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on August 19, 2010, 08:33:17 AM
I'm thinking about it. Last time I lost money with offering kits :'(. So I'm currently unsure how to do it wihtout being unfair to those who have paid their kits.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on August 19, 2010, 08:34:11 AM
@kingston: Please, can you email me your measurment results? I want to compare them with my results.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on August 19, 2010, 09:32:24 AM
I didn't save any measurements... This was a quick connection test because I have a non-standard PSU (using super regulators) and I was not sure it would work at all. I still have a ground loop issue because of this and will have to redo the PSU wiring before I can show any real results. It's pretty difficult with all the voltage sense grounds of the regulators. I think I will just disable those.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: horvitz on August 19, 2010, 09:38:47 AM
Raphael,

I know it's probably not going to be as popular as the AES option, but any thoughts about ADAT in/out?  I've been kind of sitting on the ADC boards I bought from you for a little while because of other projects and the fact that AES isn't useful to me right now.  Thanks!

  Brian
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on August 19, 2010, 10:01:31 AM
Raphael,

I know it's probably not going to be as popular as the AES option, but any thoughts about ADAT in/out?  I've been kind of sitting on the ADC boards I bought from you for a little while because of other projects and the fact that AES isn't useful to me right now.  Thanks!

  Brian

Brian, Mikkels ADAT boards: http://electronics.dantimax.dk/Kits/Digital_audio/index.html -> OptoRec and OptoGen
Title: Re: Modular multi channel DIY AD/DA Box
Post by: horvitz on August 19, 2010, 07:11:07 PM
Very cool!  Looks like that may just do the trick.  And not too expensive, either.  Thanks.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on August 26, 2010, 03:13:55 PM
Ok, anybody else having build a ADC unit?  ???

Anyway, I noticed that clocking becomes quite difficult when you try to make a really big unit. My unit has now 12 inputs and 24 outputs. It was really hard to do that with wires. It is really sensitive. As soon as you touch a wire of the clocks or it is a little bit moved because you have moved the total unit you have distorted sound. Then you have to rearrange your cables by moving them a little bit. :( This problem becomes bigger with more modules you use. Eg. with only using 4 ADC and 4 DAC modules no problem but with more modules the problem rises. Later I changed the problem with redoing the wiring. But it has eaten a lot of time to find the best wiring scheme via try-and-error.
Therefore, I decided to change my plans, and do first the design of a backplane/carrier pcb for the small modules. On this carrier board the modules can be plugged in exactly the combination you need. It will also provide a clean supply voltage for the analog parts. On one side there will be a standard connector for extentsion (eg. if you need more channels) with a second board while on the other side you'll have options for connections to the outside world (Sub-D, XLR, BNC with analog audio, AES etc on it).
What do you think of this? Interested? Useful?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on August 26, 2010, 03:25:23 PM
I have only tested a single ADC unit this far. I have two but haven't tried clocking them together because there has been advices against it (should be done with a master clock unit etc).

which brings me to the question

I noticed that clocking becomes quite difficult when you try to make a really big unit.

How did you set up the clocking? Do you have some kind of bench master clock unit, or is one of the boards a master?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on August 26, 2010, 04:27:55 PM
I tried two setup:
a) Let a SHARC evalution board generate all the clocks (MCK, BCK, LRCK) and configure all modules as slaves
b) Provide one ADC with a MCK and configure only this ADC as I2S master and forwarding the three clocks then to all other boards.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Brolik on August 26, 2010, 05:14:29 PM
I think the whole backplane for a modular unit idea is awesome. Less wiring = always better to me. Count me in for one as long as I can fit in one of Mikkels ADAT boards to get them to talk to my Digi 002.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on August 27, 2010, 12:36:03 AM
I definitely favor some sort of power/clock backplane. I'm all for a cleaner build, plus if it solves critical issues it seems more a necessity than a luxury!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on August 27, 2010, 03:46:11 AM
Would this backplane board include an actual masterclock, or just the routing? If the clock is included, I might be interested. I don't know how you would plan to set up the power rails on this board, but I hope it doesn't involve regulators. I already have my rails completely set up.

This kind of board would also be an ideal place to buffer the clipping flags to actual leds.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on August 27, 2010, 04:01:13 AM
Not sure yet.
For some people it it convenient to have the master clock on it but for other people it is not a good idea because the have their own high quality clock or want to use a wordclock input whatever.
The same thoughts about the power rails.
So whatever you do it is right and wrong at the same time. ;)
Clipping and error LEDs are already on the ToDo list.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on August 30, 2010, 07:31:20 AM
humble observations:
-it may be wise to have each backplane board able to accept at least 4 modules (since that's when it seems a board is critical).
-if clocking is included, then maybe include a clock jumper to select between master/clock through, which could feed from the extension connector you were discussing?  the clocking pinout at this connector could then be used as a word in from either the diy master or an external source to feed the other backplane boards.

this would cut down on wiring between individual backplane boards, which is the task at hand, and provide everyone the option for a master clock.  it would also net 16 channels for each backplane board, which would make for a nice molex out to DB25  ;D
as far as power distribution goes, i'd love to see local regs... but that debate is for braver, smarter men than i!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on August 31, 2010, 05:52:48 PM
got around to getting these done..
(http://farm5.static.flickr.com/4126/4946006901_404cf07136_m.jpg) (http://farm5.static.flickr.com/4126/4946006901_404cf07136_b.jpg)
(http://farm5.static.flickr.com/4086/4946007299_e6737acae7_m.jpg) (http://farm5.static.flickr.com/4086/4946007299_e6737acae7_b.jpg)

oh well.. i guess that means i'll go through with this anyway..
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on August 31, 2010, 07:06:29 PM
Gah! Baadcode, we need higher res links! :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: baadc0de on September 01, 2010, 02:28:26 AM
click on the pictures in my previous post to see larger versions.

EDIT:
humble observations:
-it may be wise to have each backplane board able to accept at least 4 modules (since that's when it seems a board is critical).
-if clocking is included, then maybe include a clock jumper to select between master/clock through, which could feed from the extension connector you were discussing?  the clocking pinout at this connector could then be used as a word in from either the diy master or an external source to feed the other backplane boards.

this would cut down on wiring between individual backplane boards, which is the task at hand, and provide everyone the option for a master clock.  it would also net 16 channels for each backplane board, which would make for a nice molex out to DB25  ;D
as far as power distribution goes, i'd love to see local regs... but that debate is for braver, smarter men than i!
Also, I agree with everything Grant said.


Cheers,
B.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on September 01, 2010, 04:12:59 AM

Looking good baadcode!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: zayance on September 01, 2010, 05:41:01 AM
Very nice work thumbs up! Got some patience.... But on the picture of the board alone i could see some solder bridges on the PCM4104, maybe because of picture on my iphone small screen, don't mean to offend maybe just the ground tabs and so it's tottaly normal  ???, just an observation,i don't think you would miss that tough   ::)  
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on September 01, 2010, 08:17:58 AM
There are bridges in several places on the PCM4104 pins. completely normal. see the datasheet.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on September 01, 2010, 08:23:42 AM
Indeed. The bridges occur due to a connection of these pins on the PCB when you handsolder them. But you have to make sure that they are only there where they should be and not somewhere else. Better you look twice... ;)
Well done, Kingston. Are they already working?

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: zayance on September 01, 2010, 09:25:52 AM
I'm out of town to be able to see the boards in front of me,  and that's what i've tought yes, stupid observation, anyway very nice work...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on September 16, 2010, 01:25:37 PM
educated myself a bit more on power regulation this morning... promoted myself from a know-nothing to a brash, fumbling novice  ;).  now for more undereducated thoughts on the backplane... i'm sure it'll be mostly trivial, but i've got a real itch for discussion on this project!
if regulation is linear, either on or off the backplane, an iteration of the jung circuit would be superb.  performance would obviously be great, so it would be more a question of cost/size/efficiency.
as far as switching options go, the ADP2114 or TI's TPS54286 offerings might be viable as well.  obviously an on-board only solution in these packages.  the power handling characteristics sit nicely for 4 converter modules, corresponding AES, and fudge factor for clock.  switching frequencies are well outside the audio band, so rather conventional filtering should take care of that.  still trying to learn up on how crucial synchronization would be for daisy chained boards, as that would steer selection toward the analog devices chip.  they happen to be cheaper and can sync to higher switch freqs, but Vin is pretty limited and they only come in 32lfcsp   :'(

EDIT: that analog devices chip wouldn't provide an elegant solution at all.  didn't take the 15V into account.  who wants to deal with solder bridges on that thing anyway...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 23, 2010, 06:33:23 PM
The project is not dead it just smells like it... ;)

During the last few weeks I designed the carrier board. Today I finished the design. Here you can see a preview of it. Tomorrow I'm going to etch that board myself.
Some features:
- takes 6 modules
- connection to the outside via SUB-D25
- connectors for daughter boards if XLRs or BNS or whatever is needed instead of SUB-D.
- all voltages for the boards are generated from the +/-15V supply via standard linear regulators (but they can be left out and replaced by a Jung-regulator or something like that)
- the board offers expansion ports to connect it to a second board, maybe you want 24 channel DAC with AES input then two of these carrier boards are connected together
- it offeres a galvanic isolation: noise in the ground system of the digital interface part cannot enter into the ground system of the DAC or the ADC.

I'll keep you informed about the progress. Perhaps some of you are interested in that carrier board.

Raphael

PS: You cannot see the slots for the modules with the size like the ADC module. These slots are on the other side of the board.



Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 26, 2010, 11:24:13 AM
Here is now my DIY-etched board. Let's see wether I can get it running or not...

Raphael

P.S.: I forgot to tell, the board will get LEDs for the Clip/Error signals.

 
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Sredna on October 26, 2010, 11:31:22 AM
Any plans on ADAT out?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on October 26, 2010, 11:43:55 AM
P.S.: I forgot to tell, the board will get LEDs for the Clip/Error signals.

Spotted those in the layout, well done all around! Don't have my schematics handy to follow traces from pinouts, did you doing anything with the clock i/o routing?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 05, 2010, 03:59:50 PM
Hi,

for long time now there have been no replies on this topic.
First the bad news: The mainboard and the group buy of the DAC modules is still delayed due to TI.
Therefore, I swiched back to the clock board in the meantime. I reworked the generation of the clocks in stand alone mode as you can see in the attached schematic and picture of the layout.
Currently I'm adding a word clock in option. In the previous version we discussed a solution built around a microcontroller. I decided to discarded that for two reasons:
1) I guess for many members it will be a big contra if you need to flash a microcontroller first.
2) I found a device that enables me to do it wihtout a microcontroller but still with good results.
I'lll keep you informed about that as soon as I've drawn the schematic.
Anyway here is the board only with the parts that are needed to generate and distribute the needed I2S clocks.
Comments are welcome.

Raphael

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 05, 2010, 04:01:27 PM
The current layout as starting point.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on December 05, 2010, 04:33:29 PM
Looks interesting. Nice to see you using a sync divider chain.

I'd recommend against using shared buffers for MCLK/BCLK/LRCLK. Ground bounce in the common supply lines will induce periodic jitter (albeit at Fs and multiples, so it depends on the modulator what the impact is). Consider single gate logic (in SOT-23-5) with sufficient decoupling, not much harder to solder than the parts you're already using. Similarly, your selectors will have some edge feedthrough, albeit much less than the aforementioned ground bounce issue.

MCLK is the most sensitive line jitter-wise.

What are the 100R input resistors expected to achieve? As placed they don't offer any characteristic impedance termination; as far as I can tell all they do now is increasing jitter somewhat (both through Johnson noise and by slowing down the edge).

Do you have any parts in mind for the clock oscillator?

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 05, 2010, 05:36:48 PM
For the clock oscillator I used FXO-HC73 from FOX. But that is not the only solution as long as it fits onto the HC73 footprint.

Which 100R do you mean? Some of them are only there to have a 0805 footprint at the place to have the option to solder a resistor there during debugging/testing the PCB. I think I'll replace most of them with 0R and kick them out in the final design.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 12, 2010, 11:40:34 AM
The schematic of the clocking board is done.
Please note that this is a version with the intionention of having it running after soldering meaning that you don't have to program a device.
We discussed DDS and Microcontroller based solutions prior maybe such a solution will come in the future. It would be nice but I've currently no concrete plans to go there.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on December 12, 2010, 06:11:37 PM
Nice.

IC17 won't be too happy with pins 1 and 4 shorted. It's not entirely clear to me why you use a comparator here, either.

Same comments I made previously on sharing buffers applies here.

Instead of IC18 you might as well use a VCXO for OSC1 (DigiKey has the ASVTX-11-A-24.576MHZ, RS have a few but the Fox ones have suboptimal phase noise). In that case you may need to square up the 0.8Vpp clipped sine output; several circuits can be found at http://www.wenzel.com/documents/waveform.html .

JDB.
[that CDCE913 does the job, but its jitter performance isn't exactly stellar]

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 22, 2010, 05:00:09 PM
Here is now the first layout for the clocking board.

JDB, do you have part numbers of the single logic parts for the output buffers?
Well I know that the CDCE913 does not perform like a DDS but I think the arrangement in a PLL like this will outperform many other designs/integrated solutions.

Raphael

P.S. The length matches the length of the mainboard. Therefore you see some unused space on the PCB but it make easier to mount and connect the PCB to several mainboards because you can do that via a rack style arrangment.

Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on December 23, 2010, 09:05:56 AM
JDB, do you have part numbers of the single logic parts for the output buffers?

74ACH1G125 (negative OE)
74ACH1G126 (positive OE)

or use simple gates, like the 74ACH1G08, so that when the driver is disabled the output isn't floating.

JDB.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on December 24, 2010, 02:22:28 AM
At the risk of dragging this thread down to a level of only slightly above that of a moron, can I just confirm where this project is up to so I can get my head around it and understand (and apologies in advance to you guys if I sound like such a fool for having to ask this)

So can I confirm the following assumptions:.

1) A/D converters kits and PCB's have been distributed.
2) D/A will be distributed when they become in stock.  
3) Both need a power supply created for them at 15v.
4) Both boards could be interfaced with a PC by using something like Mikkel's opto rec or opto gen lightpipe boards.
5) If you dont use optical adat in/ out like Mikkel's boards, the alternative is the clock board you guys are discussing here which would interface with the PC
6) Some sort of software will need to be written to get these boards to talk to the PC.


Is this all correct and am I missing anything else?

Thanks for your patience and thanks Raphael for making this project available:)

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 24, 2010, 03:46:33 AM
No Problem.

ad 1)-4) you are right.
ad 5)-6) you are wrong. The clocking board we are discussing is an option to improve the clocking (jitter) Performance and to add features like wordclock sync.
If you don't want to go via ADAT you can use the AES interface boards which are already designed and partly distributed.

JDB, thanks for the numbers, that makes it easier to find them in distrbutors inventory.
The TL331 forms a 1.8V clamp.

I wish you all Merry Christmas!

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on December 25, 2010, 03:27:41 AM
Am I right in saying that for this project, you would still need another audio interface to connect between this project and the pc- ie either connect between the audio interface with lightpipe adat or with AES?

Without an existing audio interface, is it correct that there is no other way of connecting this to the computer? Ie not like firewire etc?  

I guess my question is becuase I want an AD/DA converter that I can connect to a laptop but if the laptop only has firewire or usb connections, I may still need another audio interface that has something like firewire and lightpipe or AES connects.

Is this correct?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 27, 2010, 01:04:04 PM
Yes you are right. To use this project you still need an interface with AES or ADAT. But maybe someone Else will come with an USB solution or something like that in the future.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 02, 2011, 07:08:43 PM
Hi,

I just want to inform that I'm going to etch the first prototype of the clocking board tomorrow.
JDB please forgive me, I did change the output drivers to single gate devices because I want to test the design first before I do the fine tuning. I'm pretty shure that there will be changes... Therefore, the single gates will come in rev B. ;)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: JBVries on January 18, 2011, 12:28:56 PM
Hi Raphael,

I have been interested in this project ever since I saw the thread a while
back.

I know it's likely difficult to compare the quality/sound to anything tht exists in te consumer realm, but could you venture a guess?

Are the converters more along the lines of a Mytek or a Motu? I know those are very differed but any info you could give on the accuracy and relative quality compared to whats out there would be greatly appreciated.


Cheers,
JB
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 23, 2011, 08:42:36 AM
JB, you're read it is hard to say anything about the sound compared to Mytek or Motu. In fact I never owned one of their devices.
Anyway, from that what is used for this project (DACs, ADCs etc.) we're playing in the league of Digidesign Protools or SSL Alpha-Link looking at their spec's and what I've used.

Btw. these commercial devices are not expensive because they used really expensive converters. No. They are expensive because they use many converter chips to get many channels... ;)

Raphael

Btw. We need a name for this project. Any ideas?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on January 25, 2011, 07:17:26 AM
Yellow!

How is everybody?:) I thought to post since ethernet based connectivity seems to be a step closer. I don't know if you all are already aware of Audinate Dante, an audio over ethernet solution? I just noticed Focusrite has launched new product line that uses Audinate Dante (REDNET) and user BR seems to have some DIY friendly product coming along the line http://www.groupdiy.com/index.php?topic=42004.0  

It seems that Audinate doesn't require expensive license since they sell virtual soundcard driver and various ready made hardware solutions to transfer audio over ethernet. For example, they have card called Brooklyn that accepts I2s and has 64 x 64 IO with 48kHz sampling. One can find some sort of datasheet from support > documentation but it needs registering. http://www.audinate.com/ They also have evaluation board available.

Is anybody familiar with this? Is Dante something that DIY people can get hold to without significant monetary investment or am I just dreaming?:)

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on January 25, 2011, 09:38:07 AM

Thanks Raphael my parcel turned up today :)

I'll get thinking on the name of the project!

tmuikku : Yes - I saw the REDNET and it made me think of this project.  Could be an interesting development...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on January 25, 2011, 02:17:43 PM
Btw. We need a name for this project. Any ideas?

i vote for 'die lange reise'  ;).
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on January 25, 2011, 04:35:11 PM
Btw. We need a name for this project. Any ideas?

i vote for 'die lange reise'  ;).

Cheeky  :D
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on January 25, 2011, 04:37:56 PM
Cheeky  :D

texas instruments has been a cold, cruel mistress.  :'(
I actually meant it more as a testament to raphael's continued effort.

What about AD/DAble? Sums up (pun intended) the modular/expandable nature of the project rather well.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on January 26, 2011, 12:40:40 AM

[/quote]

i vote for 'die lange reise'  ;).
[/quote]

I like that:)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on January 26, 2011, 01:27:19 AM
I've just called it the rkn80 converter this far, when I've gathered all the documentation and needed a name for the folder.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Infernal_Death on January 26, 2011, 01:38:23 AM
Maybe A/DIY/A.

Flo
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mushy on February 06, 2011, 12:32:04 PM
Got my package. Thanks, Raphael.

I guess I should have payed attention and got an SMD station instead of the wd2 I just scored off of eBay. My bad. That certainly makes this project more daunting, but hey...  Half the reason I do DIY is to learn.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on February 07, 2011, 10:50:44 AM
Hi Raphael,

how did the initial clocking board test go? Did you get it working on the first try?

What about the plans for the "motherboards", do you first want to finish the clocking, and then move to that?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 07, 2011, 12:37:08 PM
Hi,

the clocking boards are working so far.
Regarding the mainboards I expect some prototype PCBs on Wednesday. These prototypes are smaller versions of the big mainboard with the new and final bus layout. The old one turned out to have some disadvantages. To avoid confusion: The change in the bus layout does not affect the modules there is no change needed.

Raphael


Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 17, 2011, 12:04:00 PM
Here is a pic of the mainboard prototype boards I'm currently populating.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on February 17, 2011, 12:42:31 PM
changed to 1 module per mainboard i see.  might be reading too much between the pixels, but looks like you may have made it possible to daisy chain them in a stack with headers instead of having to wire everything?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 17, 2011, 01:00:46 PM
No, two modules per mainboard because that reflects most of the orders I got.
But you can daisy chain them with headers, yes you're right.
I'll post more pictures later. That will explain it faster then writing thousand words.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on February 17, 2011, 01:09:35 PM
No, two modules per mainboard because that reflects most of the orders I got.
there's that "reading between the pixels" getting me in trouble,
But you can daisy chain them with headers, yes you're right.
and there it is making my day.  pin linkage is just about as good as continuous trace in my book, and way more convenient to rack.  well played.
I'll post more pictures later. That will explain it faster then writing thousand words.
indeed it will.  thanks for the pre-update!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 17, 2011, 01:22:40 PM
There are so many options to configure a unit based the small modules...  ::)
I think, when the final box is finished I'll use one afternoon to write down all options...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 18, 2011, 03:38:51 AM
These two boards I'll use for 4 DAC modules giving a 16channel DAC-Unit. Later I'll stuff a third one to go for 24channels...
But first let me prepare the AES input.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 21, 2011, 06:49:20 AM
Here you can see the mounted DAC modules.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 25, 2011, 05:04:17 PM
A box full with i/o modules....  ::)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on February 26, 2011, 03:11:01 PM
hand-soldered, or did you get out your apron and oven mitts  ;)?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 27, 2011, 02:16:57 AM
hand-soldered of course! :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on February 27, 2011, 03:11:08 AM
Hey Raphael

Out of interest, what circuit is on the motherboard? Power supply as well or will this be external?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 01, 2011, 04:34:00 AM
Hi,

you need to supply the mainboard with +/- 15V for the analog section (if DAC or ADC modules are used) and +3V3 for the digital section.
From the 15V the board generates the +5V and the +3V3 for the analog section via regulator circuits on the mainboard.
The other features are:
- voltage monitor for reset circuit during power-up
- several pin headers for auxiliary circuits (like XLRs, level meter etc.)
- bus interface if you want to connect several mainboards together in order to build a bigger setup
- D25 connectors for i/o
- several LEDs for status display
- galvanic isolation of analog and digital section, e.g. you use two mainboards to build an 8 channel DAC with AES input and galvanic isolation between the AES input circuit and the DAC stage (recommend). But you can also stack the DAC and the AES input modules on one mainboard to get an 8 channel DAC without galvanic isolation
- the businterface can be configured for both directions for the data lines
- galvanic isolated I2C interface (if you want to control the ADCs/DACs via a microcontroller or for new modules in the future)
- the mainboard does support either I2S or TDM format for the internal digital audio stream

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Matthew Jacobs on March 01, 2011, 04:47:35 PM
Hi Raphael

I was following this thread in the beginning but dropped out a little.

Are there boards available for this project?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 02, 2011, 07:48:40 AM
Matthew,

yes I still have PCBs for all four modules for sale. Please contact me via PM for the details, like how many you want etc.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: erikb1971 on March 03, 2011, 09:01:41 AM
jdbakker and rkn80, I send a pm to you guys, this post just in case your pm box is full...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on March 03, 2011, 03:24:42 PM
- the mainboard does support either I2S or TDM format for the internal digital audio stream

will this all end up mux'ed to single wire?

EDIT: to clarify- will the data of all the chips get multiplexed into a single stream down the line, or remain specific to the separate adc's?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on March 10, 2011, 05:40:43 AM
Shameless crosslinking to introduce this new topic about DIY Dante stuff to ADDA board audience  8)
http://www.groupdiy.com/index.php?topic=43478.0

Any name yet for this modular multichannel ADDA project? As I'm on a coffee break and sun is shining I propose a name: Modular Audio from Germany, Digital analog converter = MAGDAC :D

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 14, 2011, 04:33:13 AM
@grantlack: Well some of the TI chips do support a TDM mode that means 8 channels are multiplexed to one data stream. I wanted to open that door with the mainboard but I do not use it yet.

Anyway I attached a pic with the mainboards for the AES input mounted. Please not the different component population.

To be continued...

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on March 14, 2011, 08:28:43 AM
Do you use the same mainboard for DAC and AES in? That's handy.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 14, 2011, 08:44:18 AM
Yes.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: sr1200 on March 16, 2011, 11:45:30 AM
Im tryin to catch up on this thread and figured id ask. 
Has anyone tried using a circuit containing an AL1402 (ADAT light pipe decoder) to feed into this?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 21, 2011, 08:05:35 AM
Here is the next picture for you:
The AES inputs with some additional cabeling for testing.

Raphael

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 25, 2011, 07:47:05 AM
The AESins are now all working! :)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on March 25, 2011, 12:56:47 PM
The AESins are now all working! :)

it grows... it lives!!!
 ;D ;D ;D

have you tried using a channel from each board simultaneously then?  also curious what the final assembled height is, or more directly whether two of the assembled mainboards can stack in a 1u.  seeing this thread on page 1 always makes my day.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 28, 2011, 05:25:41 AM
Next deck. ;)

grantlank, depending on your enclosure, it may not be possible to stack to boards in a 1u-enclosure. The distance between the boards is 2cm. The distance is needed by the transformers on the AESin modules. It may work if you change the order. Not sure. I'll use a 3u but only because I want to reuse an old one.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on March 28, 2011, 05:31:25 AM
You're making one serious deck on the first try. I really like seeing this thread move, as I have populated and tested my preliminary set up of 8in 8out with AES interfaces. Of course they don't really do anything since there is no clocking yet. I did a quick hack attempt at clocking with my RME HDSP, but I'm ashamed to even mention it now. And of course it didn't work, and at least I didn't break my soundcard!

One question, these mainboards seem to be for DAC and AESin boards only (perhaps AES out, too), but how are the ADC longer/thinner boards accommodated?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ptron on March 30, 2011, 06:27:40 AM
Would this project be simple for a noob? :)

Great work btw!!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on April 29, 2011, 08:44:17 AM
Any news and experiences on the motherboard tests?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on May 03, 2011, 06:48:33 AM
I'm also keen to hear:)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on May 16, 2011, 11:16:18 AM
Hi Raphael

Just wondering if this project is still going or whether it is being buried. Everythings gone a bit silent lately.

Cheers
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on May 16, 2011, 10:06:39 PM
I'm still workin on mine! Just bought some chips the other day. Slowly collecting parts... long process! I don't have any SMD stuff before this.

Thinkin of rolling my own ADAT tx on an FPGA/CPLD.... add it to the list of to-do's haha!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on May 18, 2011, 11:51:33 PM
mmmm, so besides Guitarguy, anyone else still pursuing this project. I am concerned I may be experiencing loneliness issues...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on May 19, 2011, 05:23:08 AM
I'm waiting the motherboard. And kind of wait for a year or so if there is some news on the Dante interface ;)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Kingston on May 19, 2011, 03:10:53 PM
I'm still building this, eagerly waiting for the motherboards and clocking. But currently funds are also low so I have one variant of this project on sale in black market. If no one bites, I will end up finishing that one as well.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 27, 2011, 10:59:51 AM
Hi,

first of all, sorry for the long delay. It has been really busy here the last few weeks and therefore, I didn't make progress on the mainboards. They do work so far. Only there is a small bug in one enable line: it was floating instead of pulled down either to ground or to VCC. But anyway I'm not happy with the design of the mainboard. It is not that flexible like I want.
Besides that I did some work on an Ethernet Audio-Connection to connect the box to a PC. I think I should first finish that because it may happen that this need a change of the mainboard again. I hope that I'll find time to finish that the next weeks.
Anyway what do you think? Is it better to have a mainboard that holds many modules (like 8 modules or so) or would you prefer a small mainboard for only two modules? And who many interest are there for a mainboard?

Raphael

P.S. Regarding clocking: When you have AESin modules you can configure one of them to generate all the clocks you need.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on May 27, 2011, 11:30:16 AM

Hi Raphael,

For me personally, a mainboard will be nice nice to have, but mounting two modules is enough - I've invested in 8 channels so far and the way things are going will consider another eight maximum, so a huge motherboard would really be surplus to my personal needs. 

One critical thing for me however is the audio over Ethernet - I'm delighted to hear you've made some progress with this :)

That said, I'm out of the country and away from diy for the next three months, so my vote doesn't count in terms of what gets prioritised...

Thanks for all your continued work on this project.  It's really hotting up now!

Cheers

Rob
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on May 27, 2011, 10:51:46 PM
Hey Raph

As for me, I am fine with a small board that holds only 2 modules of either side.

Good to see this project hotting up as well. Its the most exciting thing since I accidently touched the heater windings on a fender princeton amp:)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: zayance on May 28, 2011, 05:29:30 AM
Quote
As for me, I am fine with a small board that holds only 2 modules of either side.

+1
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on June 01, 2011, 02:03:01 AM


One critical thing for me however is the audio over Ethernet - I'm delighted to hear you've made some progress with this :)




Yes this could be so much simpler an arrangement for recording remotely - ie just a macbook pro connected via ethernet cable to this AD/DA project. I am really excited to hear how this tangiblises.

Would I be right in saying that if the audio over ethernet concept was used, there would be no need for the aes/ebu or adat interfacing boards at all and the only components of this project would be:

1) Mainboards with world clock on the boards
2) AD and DA modules
3) 15v and 3.3v power supply
4) Whatever audio over ethernet circuit was required
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Yannovitch on June 26, 2011, 06:18:23 PM
Hey Raph,

First of all, just huuuuge congrats for your progress on this project !! That's what I've been waiting for years.

What I would dream of is to produce a remote controllable API 500 module with a converter and a MIDI in/out directly on the module. So I could do something like 24 preamp or more, remote controlled, directly "traduced" to ADAT.

Do you think it would be feasible to add a MIDI option to your project ? So we could control from anywhere what is doing the converter ?

If what you're saying on the first page is still valid, you would just have to translate SPI or I2C from/to MIDI messages.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on July 27, 2011, 12:04:52 PM
took a couple months off to actually get some projects accomplished  :P, the ethernet pursuit sounds awesome!  i'm clearly in the minority, but i'd give a toe or two for a couple 8-module überboards.  just out of curiosity, what sample rate are you pursuing?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on August 03, 2011, 01:20:45 AM
I am a bit lost and overwhelmed in TI chip converter data sheets at the moment. Anyone want to shed some light to me on whether the current AD and DA chips for these modules could be substituted for the newer generation ones 4220 or 4222 for AD and 1798's for DA? I am thinking about voltage and current requirements as well. My thoughts are to go ahead and substitute them but am wondering if I a missing something really obvious that would deserve me a slap.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on August 03, 2011, 01:35:19 AM
Deuce,

I'm the systems engineer for those parts. (all PCM parts). What do you need to know?

For immediate clarification, they will not be pin to pin compatible.

Cheers

/R
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on August 03, 2011, 01:39:56 AM
Ah yes thanks for that Rochey.  Yes I figured the pin outs were different and would find a way of perhaps modding this via an external small etched PCB for the new chip,  but was trying to determine whether the PCM 4220 and 1798 would otherwise electronically be compatible to fit into Raphael's circuit.  I had this sneaking suspicion that their power requirements were different and may need other circuit surgery that would make substituting them unviable.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on August 03, 2011, 01:45:17 AM
well, the max vin/vout may be different, i.e. full scale input or output voltage may be different between converters, forcing you to redo the gain resistors and filter caps in the opamps around the converters.

The PCM422x also requires a 4V analog rail, rather than a standard 5V rail. Clocks and things should be okay, but it's worth checking the ratio between LRCK and MCK... Providing RKN has used 24.576MHz clocks rather than the usual 12.288MHz, you should be okay.

My suggestion is to stick to the current design before jumping ahead. I think you'll find 118dB is an amazing starting point for diy converters.

Cheers

/R
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on August 03, 2011, 01:54:24 AM
Yes the supply rail issue was as I suspect.

Perhaps your post was the slap around the head I need to stop me going further! Thanks!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Rochey on August 03, 2011, 01:56:31 AM
glad to be of service
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on September 12, 2011, 08:49:08 AM

Quick question for Rafael or anyone who thinks they can answer it :)

I'm currently populating the DAC.  It's 0902 REV B.

Are C165 and R165 swapped on the prinout you provided for component placement?  It seems strange that all of the other components around each of the four opamps are identically placed, but C165 and R165 don't follow the same pattern.

Also, when adding the components to the rear of the board,  does the prinout show the component placements as though you're looking at the rear of the board, or from the front, 'through' the board? Hope this makes sense...

Cheers

Rob
Title: Re: Modular multi channel DIY AD/DA Box
Post by: volker on September 12, 2011, 12:24:00 PM
Hi Rob,

I don't have the boards in front of me right now, but that should be easy to determine. C165 and R165 are connected on one side, the other side of C165 goes to ground, R165 not. Should be easy to see which is which, or measure with the multimeter.

Concerning the bottom side, it doesn't matter. None of the capacitors are polarized, just solder in any way. But I would say you're looking at the rear side, not through...


Volker
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on September 12, 2011, 04:01:44 PM

Hi Volker,

Thanks for that.  Seems like what you say backs up what's printed on the silkscreen.  Just strange that the component placement changes there.

Point 2 took care of itself.  I wasn't confused over the orientation of the components, I just wasn't sure which components went in which position.  All becomes clear when you finish stuffing the boards and have 4 of one type and 8 of another left over though.

Cheers

Rob
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 09, 2011, 11:53:10 AM
Hello everybody!

It has become quiet around this project the last few weeks. It was my fault. It was a very turbulent summer this year and unfortunately I had no free time left for this project. Sorry for that. But now at the end of the year I've more free time left and I feel that this is the right time to reactivate the project!
First of all, did anybody build a converter? There have been several members who ordered converters together with an AES front end, so they should be able to get something working (even without a mainboard, just by using some flatband ribbon cables).
Anyway, since I got some messages where people asked for an ADAT interface I decided to postpone the mainboard. I have some prototypes here but there are some issues to be solved before they are really helpful. And besides that I'm now owning a new MacBook Pro and I got one of the last Presonus Firestudio LightPipes. I think it is not the badest idea to have an ADAT interface.
I'm not sure anymore wether Mikkel's boards will work because I recognized that the clocking of the wavefront devices is inverted compared to the rest of the AD/DA chip world. Therefore, I now designed my own boards. The first one is an ADAT interface with 4 lightpipe inputs (=32channels @ 48kHz) mirroring the Firestudio configuration. That board is already lying here on my desk while I'm writing this. I'm going to stuff and test it the next few days and will keep you informed. After that ADAT output will follow. As soon as I've finished the ADAT interface I'll return to the delayed parts. That is the roadmap for now. ;)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on November 09, 2011, 11:57:27 AM
Jeah! cool  8)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on November 09, 2011, 12:12:21 PM
Yay! adat would make this project perfect for me.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: letterbeacon on November 09, 2011, 01:42:08 PM
Very exciting - looking forward to reading more!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: JW on November 09, 2011, 07:35:17 PM
I gather the line amp is going to be IC opamp based? (I didn't read through all the pages, but I will) It would be awesome to have the option to use a discrete opamp, even transformers ala the burl stuff. Maybe a way to combine one of the API style boards available here if desired? I would go all out for some thing like that.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 12, 2011, 09:32:05 AM
JW, I'm not planning to do something with DOAs. All my designs are IC-based. If you want to go for that, you're welcome, but you are on your own then.
anyway here is a pic of the ADATin board I'm going to populate today.

Raphael

Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on November 12, 2011, 01:25:34 PM
Are there boards (ADC and DAC) still available for this somewhere?

This whole time I've been waiting and watching this thread, hoping for ADAT...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 13, 2011, 10:51:13 AM
yes I still have ADC and DAC boards left. I think I'll put them on the black market section next few days.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ppa on November 13, 2011, 06:26:52 PM
The schematic of the clocking board is done.
Please note that this is a version with the intionention of having it running after soldering meaning that you don't have to program a device.
We discussed DDS and Microcontroller based solutions prior maybe such a solution will come in the future. It would be nice but I've currently no concrete plans to go there.

Raphael

IC16 isn't a 4040 but a 4046
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on November 13, 2011, 07:38:19 PM
Last I heard, it was quite difficult to get adat chips from wavefont semi. Is that not true? Which chip are you using?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 14, 2011, 07:55:30 AM
Well I had no problems to get them. I just ordered them and three days later I had them on my desk.

Yesterday I finished the ADAT input board. I did a quick test on it and it seems to work: The error pin was going low as soon as I connected an ADAT stream to the board. With a scope I was able to see all the clocks and data streams that looked pretty much like digital audio. Therefore, the decoder seems to recognize an ADAT stream and decodes it. As soon as possible I'll connected it to an DAC and listen to it... ;)

Raphael

Title: Re: Modular multi channel DIY AD/DA Box
Post by: sr1200 on November 14, 2011, 09:25:26 AM
Is the card taking the clock source from the adat stream or does it have an internal clock (or options for BNC word clock)?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 14, 2011, 09:42:08 AM
This card supports three clocking options:
- Recovering the clocks from ADAT stream (one ADAT-decoder is master)
- use internal clocking of the box by setting the ADAT-decoders as slaves
- apply an external word clock and build in a word clock PCB. I once made one but I had never the time to populate that board. Maybe I will in my Christmas holiday.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: saxtim on November 17, 2011, 10:47:24 PM
Raphael,

I've been following this thread on and off since the first post.  I'm personally interested in the ADC with ADAT out, which, if I understand correctly, is about where you're up to with the project.  I'm not sure I'm ready to take on this project just yet, so I'm wondering if it is likely that you will do more board runs in the future, or if the group buys that have already happened are it?

Thanks

Tim
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tardishead on January 14, 2012, 06:36:18 PM
How is this thread coming along? Any updates on the new pcbs - clock? ADAT? and mainboards??
Has anyone got a batch up and running yet?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 15, 2012, 04:41:03 PM
Hi,

an update of the current status of the project:
I'm currently busy with building a new box with 4 ADAT inputs and 4 ADAT outputs and 32 DAC and 32 ADCs on the other side, so 64 channels in total. The first prototype of the DAC part with ADAT input (for Lightpipes) is now built on a piece of wood and working. I'm now looking for a nice case for this new box. As soon as I've it I'll show it here. Next step to go is no the conversion from analog signal to ADAT stream.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Majestic12 on January 16, 2012, 02:32:31 AM
Wow...I'm quite curious about this....I've been looking for a good AD conversion with ADAT out for quite a time now.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ptron on February 14, 2012, 06:59:02 PM
how much would it cost to do 8 channel DAC ? i can get this adat card (looks great!!)

do you sell kits? do you also do the word clock card(kit) and power supply (kit) if possible? is there info about the build? im really interested.. i just dont have any experience on SMD.

with this could i just put it all in a lil rack with its 8 trs outputs?
would this work with my rme hammerfall?
thanks a lot
Title: Re: Modular multi channel DIY AD/DA Box
Post by: r2d2 on February 15, 2012, 04:46:42 AM
any sound comparisatio with  actual "professional" ad-da  converters ?

peace
r2d2
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 07, 2012, 09:39:49 AM
Hi,

so did anybody besides me build a unit yet? Many people ordered PCBs and kits, so I assume that there should be a few members who built a unit.
Anyway I'm glad to announce that I've finished the design of the ADAT output board and I'm now waiting for components etc. pp. and some free time to build it.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ptron on March 07, 2012, 12:59:09 PM
is there still available 8 channel DA boards and an adat board?

what should i need if i want this configuration ? do i need another board to work as clock??

cheers!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on March 09, 2012, 12:02:23 PM
Hi,

so did anybody besides me build a unit yet? Many people ordered PCBs and kits, so I assume that there should be a few members who built a unit.
Anyway I'm glad to announce that I've finished the design of the ADAT output board and I'm now waiting for components etc. pp. and some free time to build it.

Raphael

Hi Raphael,

My DAC and ADC boards are pretty much done but I need the mainboard and preferably the ethernet interface before I can use the project.  That's always how I planned to use my version of the project.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: grantlack on March 09, 2012, 12:13:34 PM
Hi Raphael,

My DAC and ADC boards are pretty much done but I need the mainboard and preferably the ethernet interface before I can use the project.  That's always how I planned to use my version of the project.

this is where i'm at too, AES gets impractical for me at high channel counts and i haven't had the itch to pursue further contact with audinate.  no sense in doubling up on anything you've already got a head start on.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: michal_k on March 10, 2012, 04:37:13 AM
I am thinking about giving an xmos based usb interface a go. Would that be useful for people out there? How many channels in/out do you need?

m.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on March 10, 2012, 10:48:00 PM
I am thinking about giving an xmos based usb interface a go. Would that be useful for people out there? How many channels in/out do you need?

Funny, I've been looking at doing the same. I have their multichannel eval kit and one of their simple processor kits, and the tools installed well enough on my iMac.

The real trick is actually understanding the processor and the XC code.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 14, 2012, 07:07:36 AM
is there still available 8 channel DA boards and an adat board?

ptron, I only have one 4 channel DAC pcb left. For the ADAT there was no group buy yet. I'll offer that as soon as the ADAT out is ready and working.

what should i need if i want this configuration ? do i need another board to work as clock??

The basic configuration for you is: ADATin + DAC. You need only a power supply with +/-15V and +5V extra. You can configure the ADATin to be the master of clocking, then the internal clocks are recovered from the ADAT stream. The basic configuration can also be built with AESin + DAC. Then the AESin recovers the internal clocks from one of the AES-streams.

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 14, 2012, 07:10:22 AM
I am thinking about giving an xmos based usb interface a go. Would that be useful for people out there? How many channels in/out do you need?

m.

Well a nice idea. I do not really understand everything of the amos products. I could snot find any information about the maximum channel count they support.
Anyway, since the ADAT boards support 32 ins and 32 outs it might be a good idea to design an USB interface with the same channel i/o configuration and the same pinout of the connectors.

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on March 14, 2012, 06:12:08 PM
I am thinking about giving an xmos based usb interface a go. Would that be useful for people out there? How many channels in/out do you need?

m.

Well a nice idea. I do not really understand everything of the amos products. I could snot find any information about the maximum channel count they support.

XMOS is a processor family, and the channel count supported is more a function of USB bandwidth, and not the processor itself.

Quote
Anyway, since the ADAT boards support 32 ins and 32 outs it might be a good idea to design an USB interface with the same channel i/o configuration and the same pinout of the connectors.

I need to do some math, but I don't think High-Speed USB will support 64 simultaneous channels, even at 48 kHz.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: usekgb on March 14, 2012, 08:25:46 PM
Wow, am I late to this party!  I was searching for AD converters and stumbled upon this wonderful project.  I've pretty much taken the last several years off from DIY as life has gotten in the way.  I sure wish I would have found this when the ADC boards were still available!

Anyway, I have one question.  Without a clocking module, how do you plan on clocking the ADAT interfaces with the Presonus Lightpipe unit?  Are you going to use ADAT sync, or word clock?  I'm just asking because ADAT sync is notoriously jittery, and this would defeat the purpose of a really good converter.  I know that word clock is not perfect either, but it would be better than ADAT sync, no?

As for how long I've been away.....  I'm just now finishing up my mnats dual 1176 Rev D (ver 1) that I populated years ago.  (back when we were still on the old forum)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on March 14, 2012, 08:37:10 PM
Whether the clock be in the computer interface, or the ad/da, you have to slave something to the other, no?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: usekgb on March 14, 2012, 09:38:14 PM
Thanks for the clarification Gemini.  That's really what I meant.  The two units have to "talk" to each other somehow.

Cheers,
Zach
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ptron on March 15, 2012, 12:46:31 AM
is there still available 8 channel DA boards and an adat board?

ptron, I only have one 4 channel DAC pcb left. For the ADAT there was no group buy yet. I'll offer that as soon as the ADAT out is ready and working.

what should i need if i want this configuration ? do i need another board to work as clock??

The basic configuration for you is: ADATin + DAC. You need only a power supply with +/-15V and +5V extra. You can configure the ADATin to be the master of clocking, then the internal clocks are recovered from the ADAT stream. The basic configuration can also be built with AESin + DAC. Then the AESin recovers the internal clocks from one of the AES-streams.

R.
Hey thanks a lot! Is this project is easy to diy? I would like 8 ch DAC if poss but could go for 4 to begin with just into too many projects now to tackle a new one i think ill end up stumbling .. But this thread is nice imgoing to keep a close eye!

U planning on another run of DAC Boards?

Thanks a lot ! Great project, again.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 16, 2012, 11:49:05 AM

U planning on another run of DAC Boards?


Not sure yet. If there is enough interest I can do. A group buy makes only sense for at least 25 boards or so.

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 16, 2012, 12:06:44 PM

Anyway, I have one question.  Without a clocking module, how do you plan on clocking the ADAT interfaces with the Presonus Lightpipe unit?  Are you going to use ADAT sync, or word clock?  I'm just asking because ADAT sync is notoriously jittery, and this would defeat the purpose of a really good converter.  I know that word clock is not perfect either, but it would be better than ADAT sync, no?


No question. An extra word clock would be the better solution. But as long as there is no working board for it you need to find other solutions. Or you have to wait months if not a year before you can build your first prototype. It is a free-time project... Waiting so long is not what I want. ;) Therefore, first I'll build a unit clocked by an incoming ADAT stream and later add a word clock module.

R
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on March 16, 2012, 12:13:07 PM
XMOS is a processor family, and the channel count supported is more a function of USB bandwidth, and not the processor itself.

Quote
Anyway, since the ADAT boards support 32 ins and 32 outs it might be a good idea to design an USB interface with the same channel i/o configuration and the same pinout of the connectors.

I need to do some math, but I don't think High-Speed USB will support 64 simultaneous channels, even at 48 kHz.


Well I'm not familiar with USB. But with Firewire you can do 64 channels. But I think newer USB connections have the same or a higher bandwidth then Firewire, haven't they?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on March 16, 2012, 12:35:10 PM
XMOS is a processor family, and the channel count supported is more a function of USB bandwidth, and not the processor itself.

Quote
Anyway, since the ADAT boards support 32 ins and 32 outs it might be a good idea to design an USB interface with the same channel i/o configuration and the same pinout of the connectors.

I need to do some math, but I don't think High-Speed USB will support 64 simultaneous channels, even at 48 kHz.


Well I'm not familiar with USB. But with Firewire you can do 64 channels. But I think newer USB connections have the same or a higher bandwidth then Firewire, haven't they?

Yes, USB 3.0 Super Speed is 5 Gb/s, significantly faster than FW 800 or USB 2.0. But you won't see any Super Speed audio devices until the device controller chips are readily available.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: sr1200 on March 16, 2012, 12:45:30 PM
Then theres the "Thunderbolt" option.... (let the fireworks begin!)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on March 16, 2012, 03:31:43 PM
Then theres the "Thunderbolt" option.... (let the fireworks begin!)

Thunderbolt is essentially an extension to PCIe. So once Thunderbolt-to-PCIe bridge devices are available,  then any chips that use the PCIe bus can simply attach to it. It's actually a good thing.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: michal_k on March 16, 2012, 06:11:31 PM
How about splitting DAC and ADC into two devices. 32 channels are doable in audio class 2.0
Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on March 16, 2012, 06:19:22 PM
With most computers running 6 USB Ports, why not?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on March 16, 2012, 10:51:49 PM
How about splitting DAC and ADC into two devices. 32 channels are doable in audio class 2.0

That makes sense. Seems to me that one would usually need a lot more inputs than outputs for recording.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ptron on March 18, 2012, 04:17:46 AM

U planning on another run of DAC Boards?


Not sure yet. If there is enough interest I can do. A group buy makes only sense for at least 25 boards or so.

R.

well im up for 8 +wordclock + adat in :) i got tons of things on my plate so i can wait for more people if possible to come around

thanks!!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: michal_k on March 20, 2012, 06:15:48 AM
Xmos has just announced a new processor family: xs-1s. It has a built in usb and needs just one power supply. It looks like a perfect candidate for a diy usb audio interface (except it's in bga package).
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Lowfreq on March 30, 2012, 12:08:57 AM
There's been a lot of intelligent conversations by some intelligent people on this thread, but has anyone built the convertor yet?
In any format? AES or ADAT via the Optorec/gen board?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on April 10, 2012, 12:41:27 PM
Hi,

since some members asked about the status of the project I want to let you know that I'm going to order the prototype board for ADAT out this week. Currently I'm doing the last details on the silk screen. That means you can expect to see the first running prototype of ADAT out and ADAT in end of this month, I hope...  ;)

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on April 10, 2012, 02:16:53 PM
Hi,

since some members asked about the status of the project I want to let you know that I'm going to order the prototype board for ADAT out this week. Currently I'm doing the last details on the silk screen. That means you can expect to see the first running prototype of ADAT out and ADAT in end of this month, I hope...  ;)

Raphael

Far out!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ptron on April 11, 2012, 06:29:05 AM
Hi,

since some members asked about the status of the project I want to let you know that I'm going to order the prototype board for ADAT out this week. Currently I'm doing the last details on the silk screen. That means you can expect to see the first running prototype of ADAT out and ADAT in end of this month, I hope...  ;)

Raphael

Far out!

+1
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bremusound on April 16, 2012, 04:35:34 AM
For those who would be interested in a MADI solution:
I found a DIY 8x ADAT <-> MADI project here:

http://madi.webklik.nl/page/madi

all files available for download.

Anybody interested in a PCB group buy?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on April 16, 2012, 12:36:04 PM
I don't see how that helps when it only outputs 8 adat signals. It's seems to just add complexity. Our am I missing something?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: signalflow on April 16, 2012, 02:56:21 PM
It looks like it has 8 adat ins and 8 adat outs giving 64i/o of conversion from adat to madi.  Still, wouldn't mind bypassing the adat portion all together and just having a madi.

-Casey
Title: Re: Modular multi channel DIY AD/DA Box
Post by: volker on April 16, 2012, 03:10:47 PM
I've been looking into this. MADI is the route I want to go, unless somebody comes up with a LAN solution before I'll start working on it (should be enough time even if you start now :D). I wouldn't be using ADAT, but I²S <-> MADI directly of course. There isn't that much to it, MADI is basically I²S packages of each channel packed together into one frame plus the protocol overhead. It's not overly complex and should be perfectly doable.

But, I haven't even started populating one ADC/DAC board and I don't see that happening anytime soon. Unfortunately there's just too much other stuff more pressing. So, for anybody waiting for a working solution this calendar year, don't hold your breath ;).

I'm still a bit reluctant to pull the trigger on a MADI interface for obvious reasons, but just looking at the options: is there anything else besides the SSL MadiXtreme and the RME HDSPe MADI?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on April 16, 2012, 04:05:00 PM
What would really set this project off is a diy pcie madi interface . We need more software guys in here. people spend months developing hardware stuff, but with pirating being what it is, nobody wants to spend much time on software that's just going to be stolen unless is made proprietary to a piece of hardware/firmware.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: volker on April 16, 2012, 06:33:14 PM
I don't think this is bound to happen. Then we're back to programming a driver and might as well go the LAN way, which has the advantage of already available hardware. Also, designing a PCI(e) card isn't the most trivial task in the first place. That's why I was looking at MADI, because it eliminates these two things I can't (and don't want to) do myself.

Theft of software isn't really the problem here. Open source is doing pretty well, and that's what a DIY solution of this format should be in my opinion. There are just not the right people around here, or they don't speak up because they are busy elsewhere. That would be an enormous undertaking, which someone (possibly several people) has to start with both the expertise and the continued enthusiasm for the project. Software is in contrast to hardware a living matter that always needs maintenance and further development.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on April 16, 2012, 11:18:54 PM
Sounds like FPGA solution is the best to meet everyone's needs for this project! I'm hearing PCIe, ethernet, adat, madi, i2s, spdif, usb, firewire... How about a 'modular' FPGA board where people can pick their own configuration. This is probably an insane amount of work to implement everything that everyone wants, but it could be somewhat modular and add stuff as you go. Just spitballing... it is PROGRAMMABLE logic, afterall. With the new ARM/FPGA solutions on the horizon, the opportunities are all the more exciting.

I know a few people on this thread have mentioned about working on FPGA stuff. Just thought I'd offer to help if anyone wants to look at this option. I do IP work for a particular FPGA vendor. I'm also familiar with the mentioned ADAT design and I've simulated it successfully (in the original VHDL and I converted it to verilog too, for those who prefer).
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on April 17, 2012, 12:44:26 AM
I don't think this is bound to happen. Then we're back to programming a driver and might as well go the LAN way, which has the advantage of already available hardware. Also, designing a PCI(e) card isn't the most trivial task in the first place. That's why I was looking at MADI, because it eliminates these two things I can't (and don't want to) do myself.

I think PCIe using a Gennum part or perhaps one of the PLX bridges, and an FPGA for the special sauce, is not that difficult.

But driver development is a huge pain in the ass. Combine that with Microsoft's demand that a driver be blessed by the Mothership for use on Windows 7, and the barrier to entry gets pretty high.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bremusound on April 17, 2012, 12:34:07 PM
One good thing with this DIY MADI<->ADAT converter is that i don't need a MADI card for my notebook since i only need 24ch. I would use two of these converters, one for having a MADI output to drive a long cable from the stage to the DAW, then converting back to ADAT for using my RME Digiface (3x ADAT in). I could even split the ADAT outs for using my Mackie HDR as a backup medium. Nice and cheap.
Bypassing the ADAT portion would be a more elegant solution for having a MADI output, though.
It looks like it has 8 adat ins and 8 adat outs giving 64i/o of conversion from adat to madi.  Still, wouldn't mind bypassing the adat portion all together and just having a madi.

-Casey
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on April 30, 2012, 01:24:50 PM
So is the Ethernet option on this project essentially dead now? That's the part I was most excited about. I was even willing to jump in and try to do the FPGA stuff (I have a Digilent board - not exactly a high-end setup but it works).

I'm interested in a 8 or 12 in and 8 out interface, since my Impact Twin's mains output section and monitor controller blew. I'm now monitoring via the spare outputs via the DAW. Not perfect, it gets the job done, but I've decided I want something more robust and versatile for the future.

I'm not terribly affluent (read: dead broke), so I was hoping to avoid spending $700 on an ADAT or AES card. Especially since I can buy a Delta 1010 for $600 and it would probably be good enough.

Any chance the Ethernet option can be brought back to life?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 01, 2012, 11:45:59 AM
Well I think the Ethernet option is not completely dead but I think currently nobody has enough free time to develop it.
I still like the idea and I'm sure it can be done. Currently I don't have the time for it and I want to finish some stuff on my DIY desk before jumping into something new. I think that is the same situation like for many other members here, isn't it?

Raphael

P.S. Got an estimated delivery date for the prototype PCBs today: Wednesday next week. :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 01, 2012, 01:39:58 PM
I've already been doing a bit of research. One of the obvious problems is that I have yet to find an FPGA that can run faster than 400MHz or so, and that's not even taking propagation delays into account, so directly writing to a 1GBit line is out. I did find some shift registers and muxes that can operate at those speeds, so the obvious solution is for the FPGA to output data in parallel to that kind of device.

I'm still an EE student, so I'm sure I already look like a complete idiot to the other FPGA people around.

I'll try to find the hardware spec and timing information for the 1000BaseT spec and go from there.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 01, 2012, 06:24:57 PM
Okay, I've been thinking about this some more.

Based upon what I remember from my sysadmin days and what I'm gathering from earlier in this thread, the hardware part of Ethernet is little more than a very fast serial port, right? Which means that we'd just be bit-banging the output and then reading it in at the input. The cables also have separate twisted pairs for transmitting and receiving, so I'm guessing it's probably asynchronous as well.

Since the packetizing we're used to with normal networking is not happening at this level, we seem to have two options: 1) use an existing audio protocol, of which I gather there are several, and 2) design our own audio protocol, which I honestly don't think would be as hard as it sounds. Then again, I said that about designing the text display mode for the teleprompter that was my final project in digital design class. It did work eventually, though.

Please hit me with any thoughts and corrections.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on May 01, 2012, 06:33:48 PM
I've already been doing a bit of research. One of the obvious problems is that I have yet to find an FPGA that can run faster than 400MHz or so, and that's not even taking propagation delays into account, so directly writing to a 1GBit line is out. I did find some shift registers and muxes that can operate at those speeds, so the obvious solution is for the FPGA to output data in parallel to that kind of device.

The SERDES in the IOB of some FPGA families are quite capable of serializing at Gbit rates. Look at Xilinx Virtex-4, V-5, V-6, Spartan 6.

The FPGA has a special clock multiplying circuit that can create a serializer clock at the required high frequencies; it's only for the I/O blocks and isn't distributed throughout the FPGA on standard clock-routing resources. It's a multiple of a word-rate clock, so you load the serializer on the slower clock and the hardware serializes the word and shifts it out.

That's the gist of it, anyways; the devil is necessarily in the details.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 01, 2012, 07:22:36 PM
The FPGA has a special clock multiplying circuit that can create a serializer clock at the required high frequencies; it's only for the I/O blocks and isn't distributed throughout the FPGA on standard clock-routing resources. It's a multiple of a word-rate clock, so you load the serializer on the slower clock and the hardware serializes the word and shifts it out.

So I'd still be parallelizing the processing, but could shift to a gigabit serializer without any external hardware. That makes things a little easier.

Sadly, all I have to develop on is my Nexys2 board. I was quite serious when I said I'm dead broke. I'm still trying to find a way to finish my final year of uni.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on May 01, 2012, 08:18:15 PM
There's lots of ethernet IP out there... why would you want to code your own? No sense reinventing the wheel. Especially for the hard stuff!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 01, 2012, 08:35:03 PM
You know, I wonder if the FPGA is the right approach here.

I just found some standalone 10/100/1000BaseT Ethernet controllers on Mouser (http://www.mouser.com/Semiconductors/Communication-Networking-ICs/Ethernet-ICs/_/N-5cfym?P=1yzux2p&Keyword=ethernet+controller&FS=True) for $5-$7 apiece. Someone mentioned earlier the idea of using a microcontroller (ARM is probably the singular choice here) combined with an Ethernet controller, and I can't help but think that that really might be the way to do it. I'd be more confident with embedded than FPGAs for something like this.

To me, FPGAs are best for 1) niche designs that can't justify mask costs and 2) lower-level designs that benefit from being highly customized, and 3) where field programmability is a must. (When I say "lower level", I'm referring to complexity, for lack of a better word.) None of that really fits here.

I'm sure other people have very differing opinions, but those are mine. I'm more than happy to have my mind changed, but I just think ARM (or other suitable choice) plus Ethernet chip would be easier and faster to pull off.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 01, 2012, 09:02:43 PM
There's lots of ethernet IP out there... why would you want to code your own? No sense reinventing the wheel. Especially for the hard stuff!

Well... I found this on OpenCores: http://opencores.org/project,ethernet_tri_mode

It would well fit into the Spartan 3E on my dev board (I paid extra to get the Nexus2 with the 1200 chip), and even has its own support forum. I'd really need to dive in and see what it's doing. I'm also still digesting what Andy said about newer FPGAs and their serializing capabilities.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on May 02, 2012, 01:57:31 AM
Not just programming the ethernet chip in the breakout box, but you'd have to program custom ASIO (or something) drivers for computer OS to understand the audio box? For this reason, I still believe that the Audinate Dante is the best option for DIYer to dream of ethernet audio interface ;) Still, I don't know if even the dante is yet ok for DIY (high cost)... here's the card you'd need, no programming... http://www.audinate.com/index.php?option=com_content&view=article&id=276
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 02, 2012, 02:19:55 AM
Well, one fellow much earlier in this thread had a rudimentary driver already working, but he kinda dropped out of the whole thing, if I read it right. That's largely why I was asking if the Ethernet option was dead. I was kinda hoping I could rekindle that side of the project as well.

The fact of the matter is, I'll probably end up buying a Delta 1010. I am NOT going to spend $700 on a card with no converters which I will then have to DIY.

(But really, M-Audio? You're still charging $600 for a 15-year-old design? Sheesh.)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on May 02, 2012, 02:39:22 AM
Well, one fellow much earlier in this thread had a rudimentary driver already working, but he kinda dropped out of the whole thing, if I read it right. That's largely why I was asking if the Ethernet option was dead. I was kinda hoping I could rekindle that side of the project as well.

The fact of the matter is, I'll probably end up buying a Delta 1010. I am NOT going to spend $700 on a card with no converters which I will then have to DIY.

(But really, M-Audio? You're still charging $600 for a 15-year-old design? Sheesh.)

Sorry, forgot about the driver :) Did you get it working between two computers alright?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 02, 2012, 06:47:47 AM
Darren,

is it a solution for you to buy either a RME RayDAT or a Presonus Lightbridge and DIY the ADAT/Analog converter? Then you have more i/os then you need.

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 02, 2012, 12:54:35 PM
Not at those prices, no. That's why I want the Ethernet option: the hardware is readily available and it's definitely fast enough. Of course, the downsides are needing custom hardware in the converter, and a driver for the computer side.

To be honest, I have little faith in my ability to pull this off. And even if I do, if the driver side doesn't get done, it's all for nothing anyway.

Now, back to the actual discussion at hand: FPGA, or micro with controller chip? I think I'm still leaning toward the latter.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on May 02, 2012, 02:52:50 PM
Now, back to the actual discussion at hand: FPGA, or micro with controller chip? I think I'm still leaning toward the latter.

Doing Ethernet requires a processor to handle the IP stack. Now, if you look at all of the examples of doing Ethernet on an FPGA, they all use a processor. In the Xilinx world, that's either a MicroBlaze soft core or one of the Virtex-4 or -5 parts with a hard PowerPC core.

Having been through the sheer hell of using the Xilinx EDK, and recognizing that the cores they provide are absolute crap, we (day job) no longer embed a processor in an FPGA. (Having said that, I just finished a camera that has an 8051 core in an Actel FPGA; long story ...) Since we need an FPGA to do the magic that we do, obviously it's there. But for processing, we use either a Silicon Labs 8051 or one of the Applied Micro PowerPC processors. And the bonus with those $20 PPC chips is that they have an onboard Tri-mode (including Gigabit) MAC that actually works. Plus you can use the free GNU toolchain to do your development.

None of the ARMs that we've looked at have Gigabit Ethernet, but if 100Base-T suffices, they're an option. Silicon Labs just introduced an ARM Cortex device that looks mighty mighty interesting (and we're going to use them in favor of the 8051s moving forward for most things) and they have a nifty add-on 100 Mbit Ethernet controller that works well.

So now you're faced with a serious question: how do you get your audio data to and from the processor? None of the PPC or ARM devices I've looked at has an I2C port for converters (forget about ADAT) but perhaps they have a general-purpose programmable serial port that can be configured to look like I2S? Otherwise, you're talking about a small FPGA or CPLD to do the I2S interface, which perhaps can be connected to a DMA interface on the microprocessor.

Notice that I have not said one word about firmware that runs on the microprocessor. As it says in the textbook, "That is an exercise left to the reader."

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on May 02, 2012, 03:01:03 PM
(But really, M-Audio? You're still charging $600 for a 15-year-old design? Sheesh.)

The price is based on the bill-of-materials cost, with a multiplier to accommodate the cost of keeping the lights on and the water running in the office and all of the other overhead involved in actually running a business.

I wouldn't expect the price to drop unless the cost of parts dropped.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on May 02, 2012, 03:05:12 PM
Based upon what I remember from my sysadmin days and what I'm gathering from earlier in this thread, the hardware part of Ethernet is little more than a very fast serial port, right? Which means that we'd just be bit-banging the output and then reading it in at the input. The cables also have separate twisted pairs for transmitting and receiving, so I'm guessing it's probably asynchronous as well.

Please hit me with any thoughts and corrections.

The hardware is borderline trivial.

The software required to do whatever it is that Ethernet does is not.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on May 02, 2012, 03:12:59 PM
To me, FPGAs are best for 1) niche designs that can't justify mask costs and 2) lower-level designs that benefit from being highly customized, and 3) where field programmability is a must. (When I say "lower level", I'm referring to complexity, for lack of a better word.) None of that really fits here.

A better way to think of an FPGA design is like this: "I need to fit what used to be a rack full of TTL boards into a board the size of a credit card."

FPGAs are a design implementation mechanism. FPGA design uses the same rules as when we used to do the big VME boards full of MSI and LSI gates. It's still digital design. It's just that we can do more, and do it faster. So if that's "highly customized," so be it, but in the end, aren't most products customized?

And it's not that FPGA designs are "niche." It's just that unless you're making 100,000 of something, there's no way to justify mask costs and such. Everything I've read says that the market for structured ASICs and the "semi-custom" devices has dried up as FPGAs have gotten cheaper. So basically, if you're not a fabless semiconductor house, the pure-play fabs won't even take your phone calls.

Field programmability is actually pretty low on the list of end-user requirements.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 02, 2012, 05:06:40 PM
Do we really need to implement a full TCP/IP stack? Or can we just treat the Ethernet controller as a super-fast serial port?

Those APM chips look pretty good. Are they all BGA packages? A quick glance doesn't really say.

If you don't think this is worth the effort, then I'll stop and go back to my other projects.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on May 02, 2012, 07:04:03 PM
Do we really need to implement a full TCP/IP stack? Or can we just treat the Ethernet controller as a super-fast serial port?

I don't know what the protocol you're trying to implement involves. Things like the Aviom systems use the MAC and PHY but not the protocol, so it works for point-to-point links and in Aviom's case, specialized distribution hubs. But if you want to take advantage of off-the-shelf switches and routing kit, you have to implement a TCP/IP stack.

Quote
Those APM chips look pretty good. Are they all BGA packages? A quick glance doesn't really say.

I haven't looked; we use the BGA and to be honest, whether a part is available only in a leaded package hasn't been an issue in ages. I realize that BGA can be a show-stopper for the hobbyist trying to build a unit at home.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on May 02, 2012, 08:39:22 PM
I'm going to bow out of this for now. I won't be able to accomplish anything until I have some sort of income, anyway. So I'm going to stop talking about until I can actually make something.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 12, 2012, 11:21:41 AM
Juhu, the prototype PCBs have arrived and I'm now going to make something with them.
Therefore, I'll open an extra thread in the Lab section. For those you have been asking to see a real thing it might be interesting to follow the build process.  8)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on May 13, 2012, 08:30:49 AM
The photo story can be found here:
http://www.groupdiy.com/index.php?topic=48661.0 (http://www.groupdiy.com/index.php?topic=48661.0)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jollydowsen on May 26, 2012, 04:36:40 AM
I'm going to bow out of this for now. I won't be able to accomplish anything until I have some sort of income, anyway. So I'm going to stop talking about until I can actually make something.

well said dmlandrum . until and unless you actually implement your project all talks have no significance.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tskguy on May 29, 2012, 07:25:26 PM
You do not need to implement the full tcp/ip stack to use normal network switches. A network switch live's at the second layer of osi model and only care about the MAC address and care nothing at the protocal layer. That being said most modern managed switches can route at layer 3 but you do not have to use that feature. And using Router for this would be darn right silly.

Eric
Title: Re: Modular multi channel DIY AD/DA Box
Post by: gemini86 on June 07, 2012, 12:56:30 AM
I'm going to bow out of this for now. I won't be able to accomplish anything until I have some sort of income, anyway. So I'm going to stop talking about until I can actually make something.

well said dmlandrum . until and unless you actually implement your project all talks have no significance.

I'm not sure I'm understanding your statement correctly. Are we to stop discussing circuits or audio solutions if we have no intent and/or means to pursue them to full realization?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: dmlandrum on June 07, 2012, 06:53:49 PM
well said dmlandrum . until and unless you actually implement your project all talks have no significance.

I'm not sure I'm understanding your statement correctly. Are we to stop discussing circuits or audio solutions if we have no intent and/or means to pursue them to full realization?

Yeah, that's kinda what I was wondering. The only reason I was posting and asking questions was to see if it would be worth the time and money to pursue this project. I never really got my answer, and that's why I decided to bow out. Nevertheless, I finally have a new job that can pay for these projects, so I will be pursuing this sometime in the near future.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Lowfreq on July 15, 2012, 04:54:34 AM
Hey Raphael,

Any progress on the ADAT boards?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ricardo on August 17, 2012, 07:01:19 PM
Has anyone built and tested these PCBs & circuits?

In every case, the performance of ADCs & DACs is dependent NOT on the Golden Pinnae bits or even the chipset.  It is critically down to the PCB layout, connections & housing.  OK, the surrounding circuitry too but the former are AT LEAST as important.

Here's a DAC example by a guru.  http://nwavguy.blogspot.com.au/2012/04/odac-released.html (http://nwavguy.blogspot.com.au/2012/04/odac-released.html)  Even he took 4 PCB iterations to approach the datasheet spec.

IMHO, an ADC is more difficult to get right.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: JohnRoberts on August 17, 2012, 07:33:37 PM
Has anyone built and tested these PCBs & circuits?

In every case, the performance of ADCs & DACs is dependent NOT on the Golden Pinnae bits or even the chipset.  It is critically down to the PCB layout, connections & housing.  OK, the surrounding circuitry too but the former are AT LEAST as important.

Here's a DAC example by a guru.  http://nwavguy.blogspot.com.au/2012/04/odac-released.html (http://nwavguy.blogspot.com.au/2012/04/odac-released.html)  Even he took 4 PCB iterations to approach the datasheet spec.

IMHO, an ADC is more difficult to get right.

While perhaps apples and pears, I remember back in the day when A/Ds were made with a good DAC and a SAR (successive approximations register).  Basically you determined the bits one at a time starting with the MSB and compared the DAC output to the input. Layout of the very analog comparator and PCB very much mattered and I've seen 16 Bit products there weren't really. because of the layout...  :o

JR.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on August 18, 2012, 11:12:34 PM

Here's a DAC example by a guru.  http://nwavguy.blogspot.com.au/2012/04/odac-released.html (http://nwavguy.blogspot.com.au/2012/04/odac-released.html)  Even he took 4 PCB iterations to approach the datasheet spec.

"Extremely tiny 0603 ..."
"fine-pitch 48-pin IC ..."

oooooOhhhhh SCARY!!!!


OK, I've stopped laughing.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: ricardo on August 19, 2012, 04:06:49 AM
http://nwavguy.blogspot.com.au/2012/04/odac-released.html (http://nwavguy.blogspot.com.au/2012/04/odac-released.html) 
"Extremely tiny 0603 ..."
"fine-pitch 48-pin IC ..."

oooooOhhhhh SCARY!!!!

OK, I've stopped laughing.
Wanna post test results for your DAC or ADC?  RMAA will do if you can post a little extra data to determine where is FS.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on August 20, 2012, 02:21:37 AM
http://nwavguy.blogspot.com.au/2012/04/odac-released.html (http://nwavguy.blogspot.com.au/2012/04/odac-released.html) 
"Extremely tiny 0603 ..."
"fine-pitch 48-pin IC ..."

oooooOhhhhh SCARY!!!!

OK, I've stopped laughing.
Wanna post test results for your DAC or ADC?  RMAA will do if you can post a little extra data to determine where is FS.

That's not my point.  ::)

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on January 20, 2013, 03:08:09 AM
Is this project still alive?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 31, 2013, 06:31:56 PM
It smells dead...

But no it is still alive. Due to some circumstances there was not much time to do something on it. That has changed now. In a few weeks I'll get back my ADAT stuff that I borrowed a friend. Then I can test the final ADAT interface of the project.
The ADAT interface will provide these features:
- up to 4 input ADAT streams (lightpipe) => up to 32 input channels
- up to 4 output ADAT streams (lightpipe) => up to 32 output channels
- wordclock input
- wordclock output
- lock either to external wordclock or one of the ADAT input streams

Looking forward...

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: bremusound on January 31, 2013, 06:41:34 PM
GREAT!!!  :)

 
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tardishead on February 02, 2013, 06:30:16 AM
There was talk as well of a dac with pcm1794a
Any news on that? A similar adc would be awesome as well.
This is a really cool project. Keep it alive.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: tardishead on February 02, 2013, 06:32:24 AM
Hats off to raphael. No one has ventured on anything as good as this
Exciting stuff
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on February 02, 2013, 06:53:39 AM
There was talk as well of a dac with pcm1794a
Any news on that? A similar adc would be awesome as well.
This is a really cool project. Keep it alive.

Yes I remember that. I'm not sure yet where to go there. There is another DAC having better spec's then the 1794 but you loose then the option to do a low-cost version with the same PCB design. Anyway, nothing decided yet.
Let me first get the ADAT io working.

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on April 05, 2013, 08:24:23 AM
HI,

last weekend I was talking with a friend about this project and showed him, what I already have. And he asked, why do you not use the ADAT io board as a mainboard. You only need to extend the pcb space and add some connectors and perhaps put a power supply on that board, too. Finally you could add some routing options for the i2s signals through a fpga but that's not mandatory because it makes it complicate again.

What do you think about that? Of course it would make many things easier...

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: fret on April 11, 2013, 09:34:50 PM
How hard would it be to interface 1 each of the ADC and DAC boards from this thread with a Raspberry Pi? The Pi has a bunch of general purpose IO pins with I2C and SPI:
https://www.modmypi.com/blog/raspberry-pi-gpio-cheat-sheet

I want to make a looper with the Pi using the same chassis as my MC1 foot controller. But it needs good quality audio i/o (very low latency obviously), and at least 3 input channels (stereo instrument mix and a "drummer" mic input).
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on April 12, 2013, 04:59:13 PM
How hard would it be to interface 1 each of the ADC and DAC boards from this thread with a Raspberry Pi? The Pi has a bunch of general purpose IO pins with I2C and SPI:
https://www.modmypi.com/blog/raspberry-pi-gpio-cheat-sheet

I want to make a looper with the Pi using the same chassis as my MC1 foot controller. But it needs good quality audio i/o (very low latency obviously), and at least 3 input channels (stereo instrument mix and a "drummer" mic input).

The Raspberry Pi speaks neither I2S nor ADAT, so without jumping through major hoops it's not likely you can do this.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on April 12, 2013, 05:12:19 PM
There actually is an i2s interface. I think some people got it working-ish.

http://www.raspberrypi.org/phpBB3/viewtopic.php?t=8496
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Andy Peters on April 12, 2013, 05:15:33 PM
There actually is an i2s interface. I think some people got it working-ish.

http://www.raspberrypi.org/phpBB3/viewtopic.php?t=8496

Oh, the cheat sheet mentioned nothing about it so that's what I based my answer on.

-a
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on April 12, 2013, 05:17:35 PM
Yeah, some of the pins pull double duty so with some configuration you can get it to work. The raspberry pi wiki isn't terribly robust  :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on June 02, 2013, 09:28:19 AM
Too bad, the mainboard is actually to big. I can not find a PCB pooling service that cna make the prototype for a good price if they can make the size at all...  :'(
Let's see how to solve it.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: fenchelteefee on June 02, 2013, 12:36:00 PM
What about the real-PCB.com (http://www.groupdiy.com/index.php?topic=51628.0) guys? They seem to be quite communicative and had made already some boards for other forum members?

Title: Re: Modular multi channel DIY AD/DA Box
Post by: jdbakker on June 03, 2013, 04:32:41 AM
Too bad, the mainboard is actually to big. I can not find a PCB pooling service that cna make the prototype for a good price if they can make the size at all...  :'(

http://www.goldphoenixpcb.com/singlepage.php?tg=specialprice

JDB.
[worked well enough for me in the past]
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mrclunk on June 25, 2013, 02:39:25 PM
Hi,
a little late to the party on this one but...

With this project would it be possible to build an 8 channel AES/EBU to ADAT converter?

Need to get the AES outputs of a Yamaha AD8hr (http://www.yamahaproaudio.com/global/en/products/interfaces/ad8hr/specifications.jsp)

Into my RME Multiface 1, ADAT inputs.

I don't really need all the features of a Mutec or RME ADI4.

Edit..
Just spotted this.
http://electronics.dantimax.dk/Kits/Digital_audio/index.html
 I2s in - ADAT out.
So i could use 2 of the AES/EBU input boards. (are they still availiable?)
44 or 48kHz only.
Job done?
Be nice to have Smux 96kHz tho..
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on July 05, 2013, 11:07:05 AM
Hi,

well you can do it as you described. But please not the wavefront chips do not support I2S and their BCLK definition is different. You have to introduce an inverter.

Sorry there are currently no AES boards available anymore. Maybe in the future there will be a new run...

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: whiskeynipple0088 on September 11, 2013, 01:44:50 PM
So is this it for a DIY A/D converter
http://electronics.dantimax.dk/Kits/Digital_audio/index.html

nearly every DIY interface thread I read doesn't happen

I am extremely interested in a diy interface as I am tired of spending thousands on equipment that only lasts 4yrs. - at this point Im seriously considering going back to analog

thanks to all who have attempted and helped on this topic - its been on our heads for nearly 10yrs according to threads but seems were not that much closer - - please tell me Im blind and we have accomplished this.

(EDIT) - YES - it is still alive - ...... in the post that was directly under this one: http://www.groupdiy.com/index.php?topic=53080.0
Title: Re: Modular multi channel DIY AD/DA Box
Post by: iampoor1 on December 26, 2013, 10:00:41 PM
Any updates? Id like to build a 24in 32out converter for interfacing with a mixing console soon.  8)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 29, 2013, 07:36:40 AM
Of course yes. See the mainboard-thread. I'm currently working on a software for an UAC2 interface.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on June 18, 2014, 08:30:33 PM
Hey guys,

Finally getting to put some time into this project. Yeah... I bought the boards years ago, so what :P.

Anyway, maybe I missed it in this thread, but I can't for the life of me find the schem/BOM (specifically for the DAC boards). Yes, I see the schematic posted near the front of this thread, but Raphael mentioned that the filter values weren't correct. I know I got a hard copy of them with the boards, but again... that was several years ago now haha!

Can someone kindly point me in the right direction to find the latest docs? Thanks!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on July 21, 2014, 11:02:51 AM
Bump. Does anyone have a schematic/BOM?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on July 21, 2014, 11:06:54 AM

I'm pretty sure that they were not published online. Hard copies were sent with the kits.

Have you got in touch with Rafael to ask for replacement copies?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on July 21, 2014, 11:30:22 AM
Thanks, Rob.

Oh okay, that makes sense. Yeah, I sent Rafael an email before I posted here a month ago, but no luck. I'll follow up with him again.

Thanks again!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on July 21, 2014, 11:44:37 AM
You're in luck! Much to my amazement I've just walked into my workshop and found the DAC paperwork straight away. Can't see the ADC bits though so might not be able to help there.

Pm your email address and I'll send you some scans
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on July 21, 2014, 11:59:57 AM

You've got mail :-)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on July 21, 2014, 12:01:47 PM
Got it! That's perfect. I owe you, Rob!

Thanks again.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on July 22, 2014, 12:29:33 PM
Hi,

please can you send me again an email and write what you still need?
I cannot find your email, don't ask me what happened.

Thanks,

Raphael
Title: Re: Modular multi channel DIY AD/DA Box
Post by: guitarguy12387 on July 22, 2014, 07:19:58 PM
Hi Raphael,

Oh, no problem at all. Just sent email. Just need the ADC stuff now.

Thanks!
Brian
Title: Re: Modular multi channel DIY AD/DA Box
Post by: jaabaa on October 26, 2014, 07:29:29 PM
Hi !

I'm just starting to read this topic, but it is extremely difficult to find the current state of the project inside these ... 32 pages of single-topic!

What are the news in October 2014? Some prototypes running? How many inputs/outputs? Is there a driver needed? Which ADC do you finally use (PCM4204 ?) , what microcontroller chip is used? What kind of latency do you get on Windows computers ?

More generally : is there a website that "sums up" all the informations from these 32 pages?

Thanks a lot in advance
Baa

PS : It might be interesting to edit the very first message and to give the latest news : project still running / project closed / etc.  link to website of the project, etc.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 10, 2014, 05:01:47 AM
Hi,

currently there is no progress.
There are many reasons. At least I have the combination AES => DAC, ADC => AES running. Many GDIY-members ordered this combination, too but I've never seen somebody building this.
Then I started to make a main board. This main board was based on ADAT i/o and offered some routing. This was almost done and then the wavefront ADAT chips reached EOL. Thus, the design of the mainboard became obsolete.   :'(
Then there was question about USB connectivity. I tried to do something with XMOS but it turned out, that it is not so easy. I downloaded all the free software of XMOS but never succeeded to setup the reference design for UAC2.0 for compiling.
But, there is now the USBstreamer of minidsp. At least you can connect 8 i/os with it and they claim that you can use the USBstreamers in parallel to increase the i/o count. Currently I'm giving it a try for a job-related project.
Due to the story of the main board I'm thinking of giving it another try, too. I'm going to open a new thread about it soon.

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on November 10, 2014, 02:28:05 PM
Just a little vote of confidence for you Rafael... I bought the DAC and ADC boards but was hoping for the USB / ethernet integration that was talked about early on because I don't use adat anything. So this new development is just the info I wanted to hear. Looking forward to the new developments

Title: Re: Modular multi channel DIY AD/DA Box
Post by: tmuikku on November 10, 2014, 02:47:13 PM
Yeah, thumbs up :) I've got a kit as well. I haven't had time for diy for a while so no problem waiting for Audinate Dante ethernet solution ;)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: joaquins on November 10, 2014, 03:44:39 PM
I'm in too, I really like to use those with smux, since I have 8 I/O channels unused for it (2 toslink in/ 2 out)

JS
Title: Re: Modular multi channel DIY AD/DA Box
Post by: fenchelteefee on November 11, 2014, 03:13:16 AM
This is by far the most exciting project here on this site, at least for me. Thumbs up Raf, we believe in you! :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: chefducuisine on November 12, 2014, 04:26:50 PM
Raphael,

AES67 (Ravenna, etc.) would be a nice option and would expand the possibilities for your existing design. Live Sound / Stageboxes come to mind...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 14, 2014, 04:42:21 PM
Hahaha,

now everybody is filling the wish list?  ;D

Do you have any idea how to implement that?
Ravenna ist called 'open standard' but I've not seen a document with the full specification yet. And even if it is there, how much work would it be to implement it? And of course the hardware has to be made...
So don't expect a Ravenna-interface next month.  ;)
I don't say that it is not possible in the future.

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: joaquins on November 14, 2014, 05:57:16 PM
Oh, come on, I'm not filling the wish list, I've talked to you about s/mux already, and you were trying to implement it already. About RAVENA could be... I don't know if I can be helpful but count on me if I can do something, the digital world is not really my thing but I can defend myself there, I still think there should be someone here better than me for programing and picking parts, if you need help with the analog end or PCB routing count on me.

JS
Title: Re: Modular multi channel DIY AD/DA Box
Post by: chefducuisine on November 15, 2014, 02:49:30 PM
The AES67 documentation is available - for members - on the AES website. Do we have any AES members here?
http://www.aes.org/publications/standards/search.cfm?docID=96 (http://www.aes.org/publications/standards/search.cfm?docID=96)

The freely available first 20 pages of this doc mention a patent of Audinate (?) :-\

Ravenna is free:
http://ravenna.alcnetworx.com/infos-downloads/white-papers.html (http://ravenna.alcnetworx.com/infos-downloads/white-papers.html)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 15, 2014, 04:39:19 PM
@chefducuisine: I'm an AES member. I'll have a look at the AES67 doc. But as it is stated on the ravenna website: Ravenna is not AES67, it is compatible. So their might be minor differences. I once downloaded the ravenna white paper but it did not have enough info's to implement it. But it might have changed and I should have a look again.

@ joaquins:
Just kidding.  ;)

I'ld like to focus on the USB and ADAT connectivity replacement first, that is difficult enough...
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 09, 2014, 05:18:45 AM
I've some news:
I just ordered a prototype board for the USB connectivity. I hope that the PCB and components will arrive before Christmas so that I can do some soldering and programming during the Christmas holidays.  8)

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on December 26, 2014, 02:23:31 PM
I made an extra thread for the UAC2 interface:
http://groupdiy.com/index.php?topic=58202.msg740733#msg740733 (http://groupdiy.com/index.php?topic=58202.msg740733#msg740733)
You can follow the building process there.
For discussions about it I suggest to do it either in this thread or we open a new thread for it. I'ld like to keep the photostory thread free of general discussions about the interface.


R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: iomegaman on April 25, 2015, 02:58:07 AM
Just wanted to say I spent about 4 hours reading this entire thread, and it is amazing Rafael got as much done as he did, there were a lot of folks asking for the moon, at any rate I am currently building 2 sets (8-ADC/AES) which I will dump into my Lynx AES daughterboard (slaved to the Lynx TWO mainboard) which will give me an extra 8 channels in...

I will let folks know and do a test set up to compare with the Lynx converters as well as do some comparisons with an Apogee converter on a Mac...(I have a converter box that will let me do one channel of AES>Spdif/Optical which I can compare in the MacBook)

Besides that I have a Kurzweil that will allow me to compare it to yet another converter as well as the PCM4222 EVAl board which I can play around with the clocks I2S etc...(which has been collecting dust for many years but it does Spdif/Toslink and I2S as well as AES if I recall...

But first more coffee so I can hand solder the smd...

Wanted to say thanks to Rafael for this project, he has the patience of a god in my humble opinion and has done a great service in answering politely every question and request...

Like the majority of posters here he is quite decent.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: chartanm on June 11, 2015, 10:21:19 AM
Hello everybody,

I'm new on this forum and this post is my first one ... did'nt found a place to introduce myself ...  :-\

I read this long, long thread yesterday, and first, I must greet Raphael, it is an inclredible job !

I have lots of questions about all this stuff. I hope Raphael or anabody else can answer.

1) Developped modules :
If I understood well everything I read, there already are :
   - DAC module, which take 2 I2S stream line and create 4 (differential) analog out
   - ADC module, which take 4 differential analog in and create 2 I2S stream
   - AES module, which is a converter from/to AES to/from I2S. How many channel ?
      (I deal with I2S channel hier and 1 i2S is 2 analog channel)
      Is AES S/PDIF or something else ?
   - ADAT module which is a converter from/to ADAT to/from I2S.
      how many channels ?
   - WordClock module which can select the master clock and give it to each module and the wordClock out
   - One motherboard which is just a physical support for data and clock bus, and which generate power supplies
On this par, am I right ?

2) Under developpement modules
I read a lot about lots of modules ... usb, ethernet ... I'm sure Raphael is working on USB (and there are others questions I'm going to ask in the good thread)
... someone is working on the ethernet or is it dead?

3) Connectivity
Is there anywhere a schematic of all possible configurations ?
For example is it possible to have 1 wordClock module (I think it is an obligation), 4 ADC modules, 2 DAC modules and 1 USB module (whenit will be completed), in order to do a big "sound card" ?

4) About digital audio
I read that the clock is one of the most important thing ... can someone explaine in simple words why ?
As clock is a fast signal ... we can't do "Y" duplication with a clock cable, it needs a buffer I imagine ?
can we do a Y duplication with data signals ... for example ... 1 adc channel out goes to usb for recording and a DAC module to be monitored (it is just an example !)

Again, thousand greetings to you guys for this incredible work !

M.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rob_gould on September 29, 2015, 12:01:11 PM
8 x channels of ADC and DAC available for sale in the Black Market, just in case anyone's interested...

http://groupdiy.com/index.php?topic=60569.0

Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on November 24, 2015, 03:15:59 PM
Some exciting news:
The prototype of a new mainboard is on the way to me. PCB is already shipped, components will be shipped in two days.

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mickdundee63 on January 19, 2016, 08:50:01 AM
Are there any AES boards still available?
Title: Re: Modular multi channel DIY AD/DA Box
Post by: metalb00b00 on April 14, 2016, 09:30:57 AM
The schematic of the clocking board is done.
Please note that this is a version with the intionention of having it running after soldering meaning that you don't have to program a device.
We discussed DDS and Microcontroller based solutions prior maybe such a solution will come in the future. It would be nice but I've currently no concrete plans to go there.

Raphael

Hi Raphael,

In the schematic, you have the CDCE913 Y3 clock output as the input for 4046 phase comparator.

Because no micro-controller unit or programming is involved, hence Y3 divider value = Y2 divider value = Y1 divider value = 1, the CDCE913 factory default setting.  Which also means that Y3 = Y2 = Y1 = VXCO.

Therefore, your PLL setup is a 4046 phase comparing external word clock (48KHz, 96KHz, or 192KHz) with VXCO.

In TI Application Report "Generating Low Phase-Noise Clocks for Audio Data
Converters from Low Frequency Word Clock" (SCAA088.PDF), the PLL setup is a 4046 phase comparing external word clock with the CDCE913 Y1 clock output divided internally by either 512 for 48KHz, 256 for 96KHz , or 128 for 192KHz. And to set this internal divider value on the fly is by programming via the I2C bus pins (S0, S1, S2)

So... I'm a bit confused. Which one is correct or better?  Perhaps you can explain to this newbie :)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Elegost on October 26, 2016, 09:21:24 PM
Hello,

I would like to understand why, in this post

http://groupdiy.com/index.php?topic=35486.msg583101#msg583101

rkn80 said "I think it is not the badest idea to have an ADAT interface.
I'm not sure anymore wether Mikkel's boards will work because I recognized that the clocking of the wavefront devices is inverted compared to the rest of the AD/DA chip world. "

I'm looking at the data sheets for the Wavefront 1402
http://www.wavefrontsemi.com/DataSheetsFolder/WavefrontAL1402.pdf

and the TI PCM4104
http://www.ti.com/lit/ds/symlink/pcm4104-ep.pdf

and from what i can tell with my very limited comprehension, they both support a wordclock that is high first and left-justified 24 bit data output with most significant digit first. 

Is the problem that the bitclock signal for the 1402 is high first and for the PCM4104 it's low first? Am i reading that right?  Could that be solved with an inverting circuit between the output of the 1402 and the input of the 4104?

Thanks for any help.



Title: Re: Modular multi channel DIY AD/DA Box
Post by: metalb00b00 on October 26, 2016, 10:37:24 PM
Is the problem that the bitclock signal for the 1402 is high first and for the PCM4104 it's low first? Am i reading that right?

In left justified mode, AL1402 outputs a rising edge bit clock and the PCM4104 expects a falling edge bit clock.

Quote
Could that be solved with an inverting circuit between the output of the 1402 and the input of the 4104?

I'd probably use a 74LVC1G04 (single inverter logic) in between them, running from the same digital supply as the PCM4104.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Elegost on October 27, 2016, 01:51:46 AM
Perfect, thanks!
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Martin Griffith on November 12, 2016, 01:14:50 PM
http://www.wavefrontsemi.com/index.php?products

This part is End Of Life. Purchase is no longer available for AL1401AG. Last time purchase date for AL1402G is November 30, 2013.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: usekgb on November 12, 2016, 02:13:38 PM
http://www.wavefrontsemi.com/index.php?products

This part is End Of Life. Purchase is no longer available for AL1401AG. Last time purchase date for AL1402G is November 30, 2013.

The CoolAudio replacement is available from CabinTech in single pieces. 
http://www.cabintechglobal.com/?tab=semi&prod=V1402 (http://www.cabintechglobal.com/?tab=semi&prod=V1402)
Title: Re: Modular multi channel DIY AD/DA Box
Post by: Keox35 on March 08, 2017, 01:08:31 PM
Hi everyone,

First of all, a big congratulation to Raphael for his incredible work !

I know it's a diy site, but maybe this can be interesting : https://www.audinate.com/products/manufacturer-products/dante-brooklyn-ii (https://www.audinate.com/products/manufacturer-products/dante-brooklyn-ii)

It's a interface made by Audinate (creator of Dante) that allows any DAC / ADC to be connected to a dante network through TDM or I2S. Am i wrong or can it be used to connect the converter board you designed to a Dante network !?

Good luck for the rest,
Cheers
Title: Re: Modular multi channel DIY AD/DA Box
Post by: MetalD on June 24, 2017, 09:06:29 PM
Hi everyone,

First of all, a big congratulation to Raphael for his incredible work !

I know it's a diy site, but maybe this can be interesting : https://www.audinate.com/products/manufacturer-products/dante-brooklyn-ii (https://www.audinate.com/products/manufacturer-products/dante-brooklyn-ii)

It's a interface made by Audinate (creator of Dante) that allows any DAC / ADC to be connected to a dante network through TDM or I2S. Am i wrong or can it be used to connect the converter board you designed to a Dante network !?

Good luck for the rest,
Cheers

Having just read every post in this thread, (almost) every link, researching the technology discussed, etc. it looks like Audinate requires many hoops to be jumped through to access their technology. NDAs and the like.

It seems for now that the best DIY computer interface solution is USB. If you can wade through XMOS's documentation for code then this seems to be the best affordable product for large channel counts that doesn't require drivers or complex programming: http://www.diyinhk.com/shop/audio-kits/101-xmos-multichannel-high-quality-usb-tofrom-i2sdsd-spdif-pcb.html#/xmos_firmware-192k_8ch_out_8ch_in_spdif_out

It supports up to 32 channels with custom firmware for TDM. One possible solution mentioned in this thread is to use two separate interfaces: one for input and one for output. That is a possibility if you still need to do this DIY and need more channels than the chip supports, and most computers come with 2 USB ports minimum.

In the future I expect that AES67 will be the way to go. Dante now supports it and Ravenna has for a while. There is a product here that does 32x32 via AES67 but it isn't cheap: https://www.archwave.net/new-products-1-1/
The other communication I am interested in is Thunderbolt, but the interface chips are all BGAs, at least for now.

Not sure if any of this has been helpful, but these are my impressions of the state of an almost decade old project as of 2017.

Title: Re: Modular multi channel DIY AD/DA Box
Post by: deuce42 on October 27, 2017, 11:20:27 PM
Hi Raphael and all you guys

I found myself reading through this thread. Its certainly been a long journey. Am I right in saying that since its been so long now since your lastpost, this project is now buried or metaphorically archived into the museum of Group Diy?  It was such an amazing project and I always felt so ignorant with regard to anything digital related that I had nothing to contribute.  I still watched it eagerly to see its progress and all your pcb's and parts sat neatly on my shelf. I had hoped to make some nice ADC project to add extra inputs to my existing apogee interface. 

Is this project still being developed or has it reached its conclusion?

Cheers
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on October 24, 2018, 04:02:53 PM
Dear followers,

this project got a successor:
https://groupdiy.com/index.php?topic=68163.0 (https://groupdiy.com/index.php?topic=68163.0)
and the journey continues.

 :)

R.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on January 09, 2019, 01:17:18 AM
Started looking how to connect the ADC card I built some time ago to AL1401 ADAT converter. It seems impossible because AL1401 uses internal fixed 64fs bit clock whereas the PCM4204 fixed 128fs bit clock at 48khz sample rate (single data rate only supported). Some external logic is needed, too bad also xCORE i2s doesn't seem to support that 128fs bit clock.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 13, 2019, 08:28:15 AM
Where did you read about the fixed BCLK?
According to the datasheet it should support 64fs since the device supports i2s.
The master clock SCLKI is fixed to 128fs @ 48kHz.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on January 13, 2019, 05:25:22 PM
Datasheet p. 19 chapter Audio serial port operation:
"... In Master mode, the BCK and LRCK clock signals are outputs, derived from the system clock input, SCKI. The BCK clock is fixed at 128fS for Single Rate sampling mode."

On the next page about the same on slave mode (I take it that its not recommended as performance may degrade).

Single rate means rates below 54 khz, ADAT wants 48khz. At 96 khz 64fs bit clock is possible.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: rkn80 on January 14, 2019, 03:51:33 PM
Ah, ok. Well I was looking at the wrong datasheet.  :o

Anyway, I did run it with 64fs only and it worked fine.
Title: Re: Modular multi channel DIY AD/DA Box
Post by: mhelin on January 14, 2019, 05:23:33 PM
It might work well. Found a diyaudio.com thread on PCM4204 (PCM4202 really, it's 2-channel version, same restrictions apply) ADC at 48khz / 64fs with Arta screenshot:
https://www.diyaudio.com/forums/digital-line-level/144454-noisy-adc.html#post1911792

Not in master mode though. Got to build another ADC board to supply the clocks, have a pair of CS5394s with the Elektor ADC pcb left for that purpose.