[Ardour-Users] Ardour with multiple cheap (USB) audio interfaces.

[Robin Gareus]

On 01/11/2014 02:25 AM, ChaosEsque Team wrote:
> Hi, I'm really interested in helping people who want to use Ardour
> with multiple cheap (USB) audio interfaces. It doesn't seem very easy
> right now to do this sort of thing - in fact, I'm not even clear if
> it is possible 

It is possible, but you're quite right that it's not very accessible,
mainly  because there is no GUI to set this up. You'll need to resort to
a few terminal commands.

Ardour uses JACK, so the goal is go add an additional soundcard to jack.
There are various options to do this, most of which are described at
http://jackaudio.org/multiple_devices

> and I'd appreciate some guidance because I think
> this is really important group of people: folks that can't afford
> multichannel interfaces and lots of amps, the sort of people who
> might really be attracted to a tool like Ardour.

Fair point. As explained on the linked page, it is not ideal to use
multiple un-synced soundcards, but it can be good enough for many cases.
The easiest way to do so on GNU/Linux is to to use alsa_in/out:

First start jackd as usual with one soundcard - and then add the others
as needed.  This is as easy as opening a terminal and running
   alsa_in -d hw:1
This adds the 1st soundcard (hw:1) inputs to an already running jackd.

Instead of numeric IDs you can also use the name of the soundcard.
Device and their names can be listed with 'aplay -l'. For example

[..snip..]
card 3: UA25 [UA-25], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

in this case 'alsa_in -d hw:3' is equivalent to 'alsa_in -d hw:UA-25'

To add outputs use the sister of alsa_in: 'alsa_out -d hw:DEVICE'

Hope that helps,
robin


PS. there are ways to automate this process as well as auto-detect,
auto-launch. Yet, this is mostly undocumented territory and requires a
bit of scripting which builds upon above concept. More later if you're
interested..