[LAU] [NOOB] How to I configure jack to connect to alsa hw:0?

Paul Davis paul at linuxaudiosystems.com
Sun Mar 8 02:58:12 UTC 2015

On Sat, Mar 7, 2015 at 6:13 PM, Bill White <bill.white at griggsinst.com>

> I apologize in advance for what seems like a trivial and often asked
> question. But I can't seem to figure out even the tools to diagnose my
> problem.  I've been reading web pages and alsa and jackd documentation for
> two weeks, with no luck.
> I'm trying to configure my ubuntu 14.04 system to use my Akai EWI USB midi
> controller. I am trying to use Ted's Linux MIDI Guide
> <http://tedfelix.com/linux/linux-midi.html> to configure things. But
> before I get midi working I need to test that jackd can route audio to
> alsa, and I can't get audio ouput from jackd.
> I have verified that alsa works with pulseaudio, when pa is running. I
> disabled pa and then made sure that pa did not autospawn (autospawn = no in
> /etc/pulseaudio/client.conf.)
> I also verified that my hardware device is hw:0. It's the only HW device
> in my machine. The EWI is not currently plugged in, and it's a MIDI device
> anyway.
> When I run qjackctl and start the server I get this:
> 19:04:28.770 D-BUS: JACK server was started (org.jackaudio.service aka
> jackdbus).
> Sat Mar 7 19:04:28 2015: Starting jack server...
> Sat Mar 7 19:04:28 2015: JACK server starting in realtime mode with
> priority 10
> Sat Mar 7 19:04:28 2015: Acquired audio card Audio0
> Sat Mar 7 19:04:28 2015: creating alsa driver ...
> hw:0|hw:0|128|2|44100|0|0|nomon|swmeter|-|32bit
JACK is using hw:0.

You should check how many channels/ports show up and compare with the
number of physical outputs on the audio chipset/back of the computer (and
maybe the front too).

 With the Intel HDA in my previous machine (and ONLY that machine), the
default outputs when opened by JACK are actually channels 7&8, so to get
audio out of them, I had to move the output jack. Open the device a
different way (I can't recall the difference) and I would get 8 channels
and 1+2 went where expected.

> P.P.S.  The EWI works with alsa and fluidsynth alone, but there seems to
> be a noticable latency between fingering notes and hearing the notes.  I'm
> hoping jack will fix some or all of that.

JACK can't reduce latency. It just tends toward lower latency by default.
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