DIY A/D and DA

[alexhornbake]

Hey guys,

I have been lurking for a while, and noticed some postings about some A/D projects, but most of them are using pre-existing add on cards to give mic pre's adat lightpipe outputs.

I have been doing some research, and decided that it wouldn't be that hard to build do really good A/D and D/A. Probably start off with a stereo box with AES/EBU connections.

Anyway, I know that David hill uses Crystal Semiconductors chips in his Crane Song stuff, and I checked out the specs online, and they seem to be great. Also the company provides schematics for their evaluation boards, which are essentially functional applications of their chips.

All their A/D, D/A chips:

http://www.cirrus.com/en/products/pro/areas/mixedsig_av.html

The two that look the most Pro:
http://www.cirrus.com/en/products/pro/detail/P1024.html
http://www.cirrus.com/en/products/pro/detail/P147.html

The evaluation board schematics:
http://www.cirrus.com/en/pubs/rdDatasheet/cs43122eb-1.pdf
http://www.cirrus.com/en/pubs/rdDatasheet/cs5381eb-1.pdf

So, yea I'd love to hear what everyone thinks of this, maybe a high quality DAC could be a first project.

I emailed crystal semiconductors and asked how much it would cost to purchase an evaluation kit. If they are cheap, you could just upgrade the PS and put it in a nice case

Alex

 

[tk@halmi]

I am thiking of stuffing an ART DIO into a rack case along with my preamp. First thing would be to take the tube out altogether. Perhaps upgrade a few caps and opamps in there.
I must admit that it is a pretty tacky solution, but after the rack case is closed nobody will know there is a DIO in there. :wink:

 

[SonsOfThunder]

Two comments...sorry they are not so positive :grin:

Alex, I think you will find eval PCBs to be pretty high $$. I'd like to hear the price when you find out.

TK, I think you will probably know there's a DIO inside when you have to listen. What do they have in there for a convertor? Dumping the toob and upgrading the opamps and SMT caps would definitely be the route to go. If you are looking for a cheap D/A convertor to rack mount, I can think of at least one that will probably beat the DIO that uses B-B PCM series chip, though I can't remember the number offhand.

HTH!
Charlie

 

[pilo]

http://membres.lycos.fr/blendinpulse/adat/
schematic for an adat converter... not fully tested yet, only the AD works fine by now, I still have some trouble with the DA stuff (problem with the lightpipe).

 

[alexhornbake]

I was expecting the evaluation boards to be expensive, but if you look at the schematics for them, they provide a full implimentation of quality A/D and D/A.

What makes a great A/D and D/A? there are only so many parts.
It seems like the DIY world is a bit afraid of touching this stuff.

For a DAC:

1. The Power supply, there is no lack of DIY knowledge surrounding quality clean power supplies.

2. Anaolg filtering on the output, certainly not as complicated as an LA2A clone.

3. The DAC receiver, all digital, its either a 1, or a 0, it doesn't seem like there is much to do here, besides buy the highest quality converters available.

thats just my .02, I'm not talking about designing a new DAC from scratch, but taking existing designs provided by many DAC chip makers, and improving all the parts of the design that there is an existing knowledge base for.

Alex

 

[jameshspencer3]

My brother is a chip designer for Crystal/ Cirrus logic. if you let me know what chips you are looking at, i will see if there is anyway he ould get a discount or a free eval. board or something. I dont know what there rules are on this type of stuff so it may not work, but definatly worth the try if anyone is intrested

 

[tk@halmi]

[quote author="SonsOfThunder"]
What do they have in there for a convertor? If you are looking for a cheap D/A convertor to rack mount, I can think of at least one that will probably beat the DIO that uses B-B PCM series chip, though I can't remember the number offhand.
Charlie[/quote]

You mean it won't sound like an Apogee? :green: LOL.
The DIO uses the same Crystal converters 90% of pro-audio gear used on the market of its time.
If anyone has a good A/D board to use for DIY please don't be shy to share. :thumb:

 

[alexhornbake]

tk@halmi,

Just currious, do you know the part # on the Dio's Crystal converter??

 

[tk@halmi]

AKM4524 24-bit CODEC.

 

[alexhornbake]

[quote author="tk@halmi"]
You mean it won't sound like an Apogee? :green: LOL.
The DIO uses the same Crystal converters 90% of pro-audio gear used on the market of its time.
If anyone has a good A/D board to use for DIY please don't be shy to share. :thumb:[/quote]

That is an AKM made converter, the S/N and Dynamic range seem to be lacking, when compared to newer, higher end chips.

http://www.asahi-kasei.co.jp/akm/en/product/ak4524/ek4524.pdf

 

[Rochey]

Anyone looked at the new PCM4204 (4 channel 118dB ADC) and PCM4104 (4Channel 118dB DAC)???

Low power, surface mount and very very funky. :grin:

plus, let me quickly add - if you can design a board that realistically performs over 120dB with 5volt rails, i'll be well impressed. My understanding is that it's doable... but not for the faint hearted :

I'll just wait for PRR to correct me now :razz:

 

[alexhornbake]

Those look pretty cool, but did you notice the PCM1792??

Dynamic Range:
132 dB (9 V rms, Mono)
129 dB (4.5 V rms, Stereo)
127 dB (2 V rms, Stereo)

I didn't know that was possible, I may have to re-think my deisgn around that chip, has anyone heard it in use?

 

[Rochey]

heheheh... yes, it's a pretty good DAC. I mentioned the PCM4x04 family, simply because its a nifty new device we have.

Burr Brown/TI have always been a few steps behind with ADC's, typically crystal or AKM have been ahead. What TI _is_ pretty good at are DAC's. The PCM1792 being the pick of the bunch.

If you need schematics and BOMS of our eval boards, then i can happily get them to you.

Cheers

R

 

[kevinc]

We have a 2 channel D/A board already stuffed and ready to go. It uses the excellent PCM1794 chip with the Cirrus Logic CD8416 input receiver. There are two output stages available: a passive transformer output stage that has to be heard for you to believe how good simple can sound and a great sounding vacuum tube based active output stage. Details are at www.kandkaudio.com/digitalaudio.html.

 

[Rochey]

just worth mentioning - the pcm1794 is just a hardware controlled pcm1792...

Kev, can your board do the mono 131dB config of the pcm1794???

 

[kevinc]

No, there's no provision for the mono mode.

 

[daArry]

i take it it went well then butta?

 

[SonsOfThunder]

[quote author="buttachunk"]there is ALOT of interest in modding these DIOs in the audiophile (not neccessarily audiofool) market. [/quote] I'm not convinced of the ...phile vs ...fool when I see the RCA Inline Purifiers with "Bybee Slipstream Inside" on the same website...

Peace!
Charlie

 

[Sleeper]

I did something similar to an ART VLA comp and a PRO VLA. It sounded better, but be warned, the ART stuff I worked on had double sided thru hole boards and it was pretty tough to work on... I toasted one channel of the PRO VLA- but that will make a nice case for a Gyraf 1176 so...



On the AD DA side of things. Something I'd like to see would be a 4channel AD/DA with an ADAT connector and S/Mux 96k
I'll have to spend some more time looking at the evaluation boards and stuff, coz this is way unfamiliar territory, and I've got no idea how to make this SMUX thing happen. Anyone?

 

[pilo]

the s/mux stuff with ADAT... keep me wake up for a lot of night!
Well, I think there's 2 ways to achieve it :
the first one is using the alesis adat encoding chip, and put some logic (µP, FPGA, CPLD?) before those, and rearange the bit order coming from the ADC.
the second way is to use a FPGA, µP or CPLD alone, make it encode 96Khz adc data to ADAT.

The adat s/mux format is just the same as 8 channels, but channels 1 & 2 carry the data for s/mux channel 1, channels 3&4 for s/mux channels 2 etc. There's a pdf (http://sonorus.com/audio/smux.pdf) that explain more about s/mux.

don't forget this link for adat stuff... : http://membres.lycos.fr/blendinpulse/adat/