[pulseaudio-discuss] New user with questions on multiple USB sound devices

Dewey Smolka dsmolka at gmail.com
Mon Jan 28 18:52:12 PST 2008

Hello all,

I've discovered Pulse while trying to solve some specific problems,
and have had some trouble getting it up and running properly. But
before I try to solve the problems I'm having, I'd like to make sure
that Pulse can do what I'd like it to -- and what my reading has lead
me to believe it can do.

If there's a searchable archive of this mailing list, please tell me
where I can access it, as I was only able to find a non-searchable
archive. My apologies in advance if my questions have already been
answered and I didn't know where to look.

I've got a home studio, running Ubuntu Studio with Jack and Alsa and
recording to Ardour -- kernel 2.6.22-14-rt; Jack version 0.3.2.  Not
sure what version of Alsa, but the freshest available from synaptic.

The interface is a Lexicon Omega USB -- 4 channels in, 2 channels out.
Last weekend I picked up a Lexicon MX200 rack effect unit with USB --
it's a 2-processor reverb/multi FX unit that allows for single-channel
serial, single-channel parallel or dual channel operation. The MX200,
connected by USB, shows up under Jack and Alsa as a soundcard. Jack,
of course, is only able to deal with a single sound device at a time.

My goal is to use Pulse to manage both the Omega and the MX200 as a
single virtual device such that I can still use all 4 ins and both
outs on the Omega while also using the MX200 for send/return with
Ardour via Jack -- both as part of the same Alsa 'device'. Ideally I'd
like to use the MX200 as a dual-channel send/return plugin in
Ardour/Jack, but I'd be satisfied with single-channel as long as I can
control send levels by track.

The main question is: Is this even possible with Pulse?

It would mean managing two separate USB sound modules such that they
were seen by Alsa as a single device, and routeable by Jack without
ruining the kind of latency I can get now -- rock solid at 8ms and
stable enough for overdubs at 2ms. Latency isn't even all that
important, as I'd only be using the MX200 during mixdown. The
important thing is being able to set send levels by track.

I haven't been able to even get Pulse working reliably yet, but if it
can manage what I want to do, I'm willing to spend time tracking down
my problems.

Thanks in advance for your response.

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