Is it possible on Linux and/or Raspbian to take have two USB audio cards and reference them like:
[dac~ 1 2 3 4]
Where 1,2 belong to soundcard A and 3,4 belong to a soundcard B?
*The reason is that apparently there is massive* *price gouging on multichannel USB interfaces.*
For example, a Griffin iMic costs $40/USD. This is 2x2 of crystal clear audio. So 4x @ 2x2 = 8x8.
So the price for an 8x8 should be $40x4=$160, right? Or less. Generally you should get a price break when buying more of the same.
Yet it seems that most 8x8 audio interfaces are in the range of $600-$900!! (USD). This seems like 4x to 6x more money than it should be.
So multiple $40 2x2s would be a very cheap alternative to getting a single 8x8. If it works. (if PD supports it).
PS: in case you don't know, USB 2,0 supports lots of audio! I was worried about saturating USB bus, and having audio compete for live data from MIDI controllers. But no worries!
I just did the calculation. *Max practical from USB 2.0 is 35 MB/s*. 2 channels of 24 bit (3 bytes/sample) audio at 48khz = 2x3x48k =288kB/s for 2 channels.
35MB/288kBs=
- ~122 pairs of audio = 243 total channels possible on USB 2.0. Wow!
Streaming audio may have some overhead, but even if you knock off 1/3 of that, still leaves a lot of room.*
*USB 1.1 would be 243/40 = 6 total channels. (e.g., 2 in, 4 out).*
*So you definitely want to be running USB 2.0 if you are running 2in x 2out
- midi controllers. *
I know lots of people using USB audio on the Raspberry Pi report having problems running at USB2.0 "High Speed" = 480 Mbit/s, and have to set their interface to USB 1.1. (12 Mbits/s). But I am so-far able to run at full USB2.0 speeds with my Pi-2 and the Griffin iMic.
The Pi-2 will DEFINITELY keep up audio-wise, as my latest patch (12-channel flanger) has at least 12 discrete channels of audio simultaneously at one point, but there are many more internal nets running audio.
I think most complex patches could easily have 24-50 internal nets running audio. Which means even on a Pi-2, PD can definitely do complex stuff and still easily support e.g., 8in x 8out.
So the theory is all there--- has anyone done it?
(Cheap multi-channel audio with PD over USB 2.0 using multiple sound cards... or any other solutions???)
Thanks! BH