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

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They are: +/- 15V (or +/-12V) for analog domain and  +5V min. for digital domain.
There is also an option to run the AD/DA boards with +12V only.
 
@all: I am currently preparing the beta release. What do you think: Does it make sense to combine the basic configuration of USB Interface and one AD/DA board on one big PCB (thus, the two PCBs in the picture above a merged to one PCB) and add the other channels (analog or digital) by expansion cards? That would simplify the wiring a bit.
 
This would mean USB interface plus 8 in 8 out on one board and each expension cards would also be 8 in 8 out?
 
Thanks for the power info.

I might be off base, but wouldn't there be an option of digital or analog I/O?  If so, then it might be a good idea to keep the interface separate from the I/O.

I would maybe imagine an analog only I/O interface with 8-32 I/O's or maybe 16 Analog and 16 digital, or solely digital I/O.

Perhaps separate is best.
 
I am already working on a 8io AES3 (S/P-DIF) board that can be used instead. But that will still take some weeks. I want to finish the USB and the analog I/O boards first.
 
Having things separate and modular is good.

I would be interested in something straightforward,  8 or16 channel d/a, aes in,  analog out.
 
Well. the 8 outputs would probably be enough for many so what would be needed is just more A/D channels. AFAIK there are no multi-channel ADC's available anywhere but there are many multi-channel DAC boards (miniDSP,  DIYINHK etc.). Also there is a slightly better AKM ADC chip available, the AK5578EN which is pin-compatible with the AK5558, and it's not much more expensive ($10 to be exact). However, if the PCB manufacturing cost is about the same for bare A/D vs. combined board it doesn't really matter. Just wondering the need for the FPGA or DSP as the XCore processor is quite powerful, on Diystompboxes there is another Xcore project where one is being used for cabinet simulation and guitar fx (http://www.diystompboxes.com/smfforum/index.php?topic=114354.0), also there is software for ADAT I/O.
 
Btw. regarding the converter specs, the AKM ADC's have fancy parallel modes which allows for higher SNR when less channels are used. So for an example AK5578 in 8:1 mode can have 130 dB SNR, and the AK5558 in 8:1 mode 124 dB (127 dB and 121 dB in 8:2 mode). So even the lesser part can be used for very high quality stereo recording (at least if other design details allows it).
 
If you considered a standardized footprint for the I/O modules, then you could potentially design a backplane and metalwork that would allow modules to be inserted into a chassis as needed.

Something to ponder.

Speaking of.  If you have some mechanical dimensions for the boards I might be able to get some traction on a rack enclosure for this.

 
Finally the ADC and DAC chips are available again at digikey. Thus, I can continue with building the prototype.  :D
Meanwhile I changed the design a bit to make wiring/stacking easier. You can now connect up to 8 expansion modules to the UAC2 core with a maximum of 32 audio channels in and 32 audio channels out. An audio interface with 32 in and 32 out now easily fits into a 1U rack enclosure.
@James: The board dimensions are:
AD/DA expansion: 120mm x 120mm
UAC2 interface old board: 100mm x 100mm
UAC2 interface new board: 74mm x 240mm
PCBs are already ordered and should arrive in a few days.

R.
 
dasnevestheo said:
This is amazing ! images from original post are unavailable for me, how does it look ? :)
+1!!

Plus, not sure this was discussed before, but, curious how are you balancing I/O ??

Is there software written for it?? is it open ?? could we take a look?

Interested in this project too!
 
Yes. I made a lot of progress with prototype B.
I am currently busy with the last few bugfixes and preparing everything for final release (BOMs, Gebers...).
I expect that end of June UAC2 interface board and AD/DA board are available for those how want to build it.

R.
 
Made some progress today:
In case that the DSP is not used, the USB microcontroller needs to talk directly to the DACs, but the microcontroller does not put out the TDM stream in a way the DAC understands. It is not implemented in the DAC. Well, the DSP can output the right signals for the DAC... Instead of hacking the manufacturers libraries for the microcontroller  I made some VHDL code that converts the signals for the DAC.
In detail: The microcontroller puts out the data with on BCLK period  delay after rising edge of LRCK while the DAC only supports data without any delay after rising edge of LRCK.
Took me an afternoon, to find this out.
 

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