XMOS-based Asynchronous USB to I2S interface

[Lorien]

@ soundcheck: For now all that this card can offer is 2 channel @ 24 bit / 192 KHz (as per XMOS reference design). Yeah, I forgot: drivers for Windows (FULL versions) and native support for MACs 10.6.3 or later.

And speaking of that, I've been asked a lot if this card can be isolated from USB bus. Well, my answer is this: to date I don't know a chip that will isolate USB and work at high speed (480 Mbps) but there's an alternative: ADI's ADUM4160 but works only in USB low/full speed modes, so no more 24@192. From what I know the limit is 24@96... it's all that you can have using it.
I have another ideea which I guess it's an option for others too (TP? :
AC-coupled differential signaling on I2S lines - including all the clocks and additional signals using LVDS, MLVDS, (?)ECL, or whatever buses you want (still - some induce a lot of jitter compared to others ), perhaps realigned on the receiver's side using the master clock source (as regal wanted). This is what I'll implement in near future but for now I have to keep my promise to some of you and build a revision to this card with total costs of 99 Euro... while (trying to) enhance the I2S output signals and (maybe) my beloved SPDIF output as well.
Choosing the chips that I want for differential signaling will rise the costs considerably so it's not an alternative for now.
Cheers,
L

[Emphrygian]

@soundcheck and Lorien
The card should work well with Linux as well since newer versions (since sometime 2010 I think) of ALSA fully supports USB audio class 2. I don't have an interface to test with, but worst case scenario AFAIK you're limited to USB audio class 1 which would limit the output to 24/96 (see for example here). Unless someone has tested and have evidence of the contrary, this is my belief.

Anyway, when the revision arrives it's very likely I'll order and build one to use with my linux pc, so if you can wait I can be the guinea pig

EDIT: ALSA seems to have full USB Audio class 2 support since 1.0.24 according to the info I can find.

[rsdio]

Lorien, are you selling this board? It looks rather expensive with double-sided SMD placements. I followed the links to the XMOS USB Audio 2.0 Reference Design at $149, but that does not look nearly as extensive as your design.

P.S. I reached this thread because someone suggested your board to someone interested in I2S output, which is what made me think that your board was available for purchase.

[Lorien]

You will be surprised to know that in fact it's a little cheaper that XMOS version
Here are few details.
Kind wishes,
L

[rsdio]

Originally Posted by Lorien

You will be surprised to know that in fact it's a little cheaper that XMOS version

Surprised? Well, yes and no. Your board is expensive to make, I'm sure, but I also realize that smart people can find a way to make even high quality electronics affordable.

P.S. Duh, I somehow missed the fact that this thread has more than one page. I feel like a newbie. As soon as I followed your link, I realized that I have four more pages to read to catch up. Thanks for your patience.

[Lorien]

Your board is expensive to make, I'm sure, but I also realize that smart people can find a way to make even high quality electronics affordable

Yes, I agree with you!... but I was talking only about WaveIO board compared to XMOS reference card... without getting into discussion what other smart peoples can / are able to do.

[Duwenbleidd]

Emphrygian - no need to worry, WaveIO works just fine with linux - tested on Ubuntu 11.04.

[barrows]

not think that Lorien's USB board is overpriced in any way, in fact, I believe he is offering this board at a very, very reasonable price for what it is.
If you compare to any other XMOS based solutions, I think you will find Lorien's price to be a very good deal. Please Lorien, do not be discouraged by those wanting a "cheaper" board; and for your next revision, please go ahead and use more expensive parts where they will make a difference in performance, and raise the price accordingly. I see your work here as a premium solution, for those looking for the best possible performance.
There are plenty of average performance USB solutions available from China for those looking for a cheap computer audio interface.

[Wolfsin]

@barrows

You are absolutely right. Even thinking about USB had in the past given me a case of the jitters. Lorien has done the heavy hardware lifting while I listened to music. I can hardly wait to ship money his way in exchange for an opportunity to enjoy future listening even more!

I had always thought isochronous firewire would be needed to get the kind of performance this board promises. I will be delighted to be proved wrong! Admittedly many changes in drivers and silicon have been required to make the insight possible for Lorien but he is delivering.

I remain convinced that 'intelligent upsampling' rather than mere interpolation for redbook music can be performed in software, possibly by preprocessing, but really needed the bandwidth Lorien is making possible to test my theories.

[deandob]

Lorien,

Looks like you are putting together a quality design & hardware.

Do you have a list of the updates for your next board revision and an ETA?

Also, regarding USB isolation, can't you use the same GMR solution that the exadevices board is using (which goes up to 384Khz)? Even if it adds a little to the cost, people will pay extra given the premium design you are putting together.