Re: [LAU] Open Sound Interface project beginnings

On Sun, Oct 30, 2011 at 8:56 AM, Emanuel Rumpf <xbran@web.de> wrote:
> 2011/10/20 Charles Henry <czhenry@gmail.com>:
>
>> ... feedback for a project, namely building an
>> audio interface, with the goal of creating freely available schematics
>> and code ...
>>
>> The concept is to create a modular and scalable system that allows
>> users to create a sound interface with an arbitrary number of
>> input/output channels.
>
> Great project !
> Maybe try some fund-raising ?

Good point. That's a consideration that needs to be up front.

> Now, say thanks to those xmos people, they have a
> whole reference design ready, inclusive buyable prototype:
>
> http://www.xmos.com/products/development-kits/usbaudio2mc
>
> Note: This is based on xmos technology, XC - a C like language, that
> allows implicit parallel programming.
>
>
> I heard USB-Audio-Class-2.0 is already supported by ALSA (driver architecture),
> thus this device might work OOTB or with very little effort on linux.

I am floored. This leaves me about speechless. It's possibly a new
direction to go--the processors themselves are about as expensive as
FPGA chips.

> In the following, some of my ideas:
>
> You could take it as base,
> - modularize it further
> - or add some missing components,
> - make IOs balanced,
> - add ADAT
> - add AES3, (AES/EBU)
> - add AES10 (MADI)
> - add AVB
> - support MIDI IO
> - Allow the synchronization of two or more cards, to allow more than 6
> IN channels.

That's clearly just for the development board--I think their
processors can handle more channels, but the $350 development board
will support up to 6 channels. It would be better to develop some
board designs around the chips, and see how the cost comes out.

> - Make most of it optional and modular.
> - Make 1 (extensible) low-cost  + 1 (all-incl.) high-end design

Yes, I tend to agree. There's several different processors in their
product line, and it's a good development platform to look at tiered
approaches with different goals.

> Since most of the modules exist, work is to connect and integrate all of it,
> and the design of a beautiful case and package ;)
>
>
> I would make most of the design digital, with the exception of pre-ADC
> (analog limiter, balancer) and post-DAC (amplifier, balancer) stages.
>
>
> You would end with about these modular stages:
>
> - analog inputs ADC_01 ... ADC_XX
>
> - ADCs would deliver I2S streams, send to a mixer (fpga ? or xmos uC)
> , or directly to output modules.
>
> - digital IO SPDIF
>
> - digital IO ADAT
>
> - digital IO AES3
>
> - digital IO AVB
>
> - digital IO USB 2.0
>
> - digital IO IEEE 1394 (maybe)
>
> - digital word clock (75Ω BNC)
>
> - analog outputs DAC_01 .. DAC_XX,   would receive digital I2S streams
>
> - controler , routing-, configuration- and switching module
>
> Digital INs would be routed to the mixer stage.
> Digital OUTs, could optionally be routed back to the mixer stage,
> maybe with a feedback-loop detection, to prevent damage of ear and device.
>
>
> --
> E.R.

Thanks for your feedback, Emanuel. It's sort of a game-changer to me.
 Clearly, there's no point in starting a project that would duplicate
an existing solution. I appreciate new information like this.
I'll have to think this over for quite a while to see which way I'd
want to go--whether there's a worthy project goal in an FPGA based
design that cannot be more easily (or more cheaply) accomplished.
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Received on Wed Nov 2 04:15:01 2011