jackd for 2 soundcards

[markbuntu]

You should be able to patch directly to/from the hardware with Patchage or JackEQ. I am not very familiar with jack because I have not used it for a while but one of those should do the trick for you.

[Stochastic]

1.jackd 109.0 can't find alsa module

The most common cause of this error is that another program is locking up the alsa driver. Quit all sound applications before attempting to start Jack. One that many people don't think about is FireFox (or other browsers).

As for the /dev/dsp thing; when I run lsof /def/dsp it returns nothing - even when I have music playing. I don't know enough about that command to troubleshoot your error.

[thorgal]

/dev/dsp is either the block device for the OSS sound driver or a fake one emulated by the ALSA OSS emulation layer (or oss2jack, which is not the case at all here).
/dev/dsp is not needed at all if you use ALSA without OSS emulation. jackd does not need it at all either, jackd uses an audio backend that can communicate to the sound system, be it ALSA, OSS or PortAudio). So unless you use an application that can only output to /dev/dsp, there's absolutely no need to have it. It's a rather deprecated thing.

[bsantos]

I got 3 cards to work with the following (I just use it for playback, great for mixxx):

.asoundrc

pcm.multi_playback {
  type multi
  slaves.a.pcm hw:0
  slaves.a.channels 6
  slaves.b.pcm hw:1
  slaves.b.channels 2
  slaves.c.pcm hw:2
  slaves.c.channels 2

# First 6 channels of first soundcard (playback)
  bindings.0.slave a
  bindings.0.channel 0
  bindings.1.slave a
  bindings.1.channel 1
  bindings.2.slave a
  bindings.2.channel 2
  bindings.3.slave a
  bindings.3.channel 3
  bindings.4.slave a
  bindings.4.channel 4
  bindings.5.slave a
  bindings.5.channel 5

# First 2 channels of second soundcard (playback)
  bindings.6.slave b
  bindings.6.channel 0
  bindings.7.slave b
  bindings.7.channel 1

# First 2 channels of third soundcard (playback)
  bindings.8.slave c
  bindings.8.channel 0
  bindings.9.slave c
  bindings.9.channel 1
}

ctl.multi_playback {
  type hw
  card 0
}

Based on http://www.sound-man.co.uk/linuxaudio/ice1712multi.html but adapted for my setup and only playback.

I then use jack with the following .jackdrc:

/usr/bin/jackd -R -m -dalsa -P -dmulti_playback -r48000 -p1024 -n2 -m

I use 2 cheap usb sound cards and choose the outputs 7-8 and 9-10 on mixxx for master and monitor.

It also works well on my setup for playing around with audio production (seq24,hydrogen,nekobee,zynaddsubfx,jamin,jackeq,p atchage). On the Macbook the "line as output" option doesn't work since the line is muted when using the headphone jack, and I couldn't use it for monitor.