[Infinitas]: USB Audio Class 2 Interface, 32 in, 32 out, DSP

[dasnevestheo]

that's why i do that. i've been using it for so long i know some very cheap and reliable brands.
most film and electrolitic capacitors are now Panasonic and Nichicon, which is nice

 

[LCoggan]

So I’ve just skimmed through this thread and the old one and had to create an account so I could join in.

I’ve been struggling for ages to find a cheap way of recording multiple audio channels on to my computer and keep them separate. After finding out how expensive it was going to be I did my usual thing of thinking ‘well surely it can’t be hard to just make one myself’. After a small amount of research I soon realised how complex this subject is and how wrong I was about it not being difficult.

Then I stumbled across this feed and my prayers were answered. I was so close to believing I was the only person ever to have such specific needs and a desire to DIY. 

I’ve had a quick look at the Infinitas boards and I’m not 100% what specifically they allow for. My personal needs are multiple XLR inputs (around 12 at least), and a USB output that I can connect to my PC to record all the channels as separate tracks. Will Infinitas cover this?

I’m very interested in this project (especially considering it saves me doing the R&D myself, not that I wouldn’t enjoy the process, I just have a busy life). Really looking forward to hearing back from you.

Liam.

 

[rkn80]

Liam,

nice that you found this thread!

For your configuration you would need the [Infinitas] core board and two Analog-IO-x8 expansion boards. That will give you 16 channels In and 16 channels out, full-duplex, all balanced.
For XLR you can either use a standard Sub-D-to-XLR cable (Tascam pinout) or connect the XLRs directly to the IDC connector directly behind the SubD on the PCBs.

Raphael

 

[dasnevestheo]

But keep in mind that those are Line inputs. If you are pluging microphones, you need a microphone preamp between the microphone and the infinitas input

 

[bernatvm]

Do you need any special tools to program the chips or they are programmed already?

 

[LCoggan]

Thanks. Could I use a standard amplifier circuit as a mic preamp with gain control on the output or is it more complex than that? Do you think I’d be better off with an opamp?

 

[rkn80]

Do you need any special tools to program the chips or they are programmed already?

You need am xTAG to program the XMOS-device for 19$ from digikey as stated in the documentation.

If you want to use the DSP option you can either use a USBi ( from Analog or from the freeDSP project) or program the DSP via the XMOS device on the [Infinitas] core board. For the second option you don't need an extra tool once you have the xTAG programmer.

 

[rkn80]

Thanks. Could I use a standard amplifier circuit as a mic preamp with gain control on the output or is it more complex than that? Do you think I’d be better off with an opamp?

The only requirement is to have a +6dBu output balanced at the output of your mic preamp. How you make the mic preamp is then a question of your personal taste.

 

[iampoor1]

Where are you guys sourcing the AK4558 from? Digikey in the USA doesnt have any stock and a 20 week lead time.

 

[dasnevestheo]

no clue yet...

 

[iampoor1]

Hmmm,Im beginning to wonder if the 4458/2/4/6 is being discontinued. Looks like digikey has ever other 8 channel DAC AKM makes in stock!

 

[rkn80]

Hi,

too bad, digikey is the only source for the AK4458 in very small quantities.
I saw this issue happening with digikey earlier already, sometime they just run out of stock. In December the AK4458 was still available.
According to the AKM website the AK4458 is not EOL. And it is unlikely because they have no 8-channel replacement yet.
According to digikey the AK4458 can be delivered on 2/20/2019. I just put one in my basket and checked delivery time.

Raphael

 

[rkn80]

You need am xTAG to program the XMOS-device for 19$ from digikey as stated in the documentation.

If you want to use the DSP option you can either use a USBi ( from Analog or from the freeDSP project) or program the DSP via the XMOS device on the [Infinitas] core board. For the second option you don't need an extra tool once you have the xTAG programmer.

I am sorry, I forgot to mention that you also need a usb-to-serial adapter like a ft2232-board to program the FPGA. These boards can be ordered for a few $ from many suppliers. Usually makers have such a device in their toolbox.

 

[mhelin]

If the AK4458 is unavailable you can use the 6ch version AK4456 which is available on digikey. Obviously you loose 2 channels then. Check datasheet, you'll need just couple of 0 ohm resistors more.

 

[saleksin]

@rkn80
First - congratulations for a very good project, and thanks for sharing it!
I have 3 questions about it.
1. You wrote, that you are working on another digital interface. Have you thought of implementing AES50 interface?
2. Where are you going to plug another digital IF? Is it going to be one of expansion headers, with cost of decreasing analog interfaces, or you are going to design another main board?
3. Could part of design with processor, along with software, be treated as digital audio interface to UAC2, like CP2615 chip?
Thanks in advance for you answer!

 

[rkn80]

First - congratulations for a very good project, and thanks for sharing it!

Thank you.

1. You wrote, that you are working on another digital interface. Have you thought of implementing AES50 interface?

No I did not think about AES50 yet. I am planning ADAT and AES3. These will be expansion boards.

2. Where are you going to plug another digital IF? Is it going to be one of expansion headers, with cost of decreasing analog interfaces, or you are going to design another main board?

The digital IO expansion boards will be connected on the expansion headers. Because there are 8 expansion headers on the current mainboard  you don't need to decrease the number of analog expansion boards. No need for a new mainboard.

3. Could part of design with processor, along with software, be treated as digital audio interface to UAC2, like CP2615 chip?

Yes the mainboard itself is something like the CP2615, but with more channelsand UAC2 support and a DSP option.

R.

 

[kolabaer]

Hello,
What parts for the power supply do I actually need?

Infinitas + 4 x 8 io

Thank you for this nice project and for your answer
cheers

 

[dasnevestheo]

i think a good quality switching PSU should be nice

 

[kolabaer]

i think a good quality switching PSU should be nice

Thank you for your fast reply!
I have one more question: Can I send 12v to the infinitas and send them through to all 4 "8I/O" boards?

"The AnalogIO-x8 board accepts +/-12V... +/-15V for the analog power supply. In case you only have a +12V supply coming from your freeDSP board you can mount the single supply option around IC104. In this case you need to populate R102 and R105 with 0R00."

 

[dasnevestheo]

it seems so