[LAU] I really need help with jack

david gnome at hawaii.rr.com
Sun Jan 27 03:36:22 UTC 2013

On 01/26/2013 02:04 PM, Bob van der Poel wrote:
> On Sat, Jan 26, 2013 at 4:27 PM, Kaj Ailomaa <zequence at mousike.me> wrote:
>> On Sat, 26 Jan 2013 23:36:32 +0100, Bob van der Poel <bob at mellowood.ca>
>> wrote:
>> No need to use jackd with audacity, unless you are thinking of feeding it
> Well, that would make life easier ... if I could get things to work
> without it :)
>> audio from other software - in which case I would recommend using a DAW, not
>> an audio editor like Audiacty. Something like Qtractor or Ardour may suit
>> you better.
>> Also, why not use a jack control application, such as qjackctl?
> Yeah, I tried qjackctl and get the same problems ....
> All I really want to to do is to record a single, mono track using a
> usb adaptor connected to a mixer. AND play back a stereo track to the
> same device. Here's the rub ...
> 1. If I play and record using audacity though the behringer uca202 I
> get awful chattering on the record. Just recording is fine, playback
> buggers things.
> 2. So, I have audacity play out on the existing audio speakers and
> record via the usb. That works, but I don't have software monitoring
> of my record. I'm playing a sax ... putting on headphones and
> listening to the background and not really hearing what I'm playing
> results if truly out of tune sax playing ... I was starting to think I
> was just very bad :)
> 3. Enabling software monitor in audacity results in too much load, and
> the recording goes to shit again.
> So, I thought that I'd try jackd ... now have more problems :)

I record regularly (and play back) using JACKD, Audacity and a UCA202. 
I'm using Debian Sid WITHOUT PULSEAUDIO or an RT kernel.

I use QJackCTL to start JACK with these settings:
Server prefix: "/usr/bin/jackd -S --realtime
Realtime box: checked
Priority: DEFAULT
Frames/period: 1024
Sample Rate: 48000
Periods/buffer: 3
Dither: None
Audio: Duplex
Input device: hw:1
Output device: hw:1
Channels I/O: 2 (for both)
Latency I/O: Default (for both)

This gives me a latency of 64 msec. It works. When I try to go lower, I 
start having problems.

Another note: The input/output device names might be different. If you 
click on the ">" button beside the input/output devices in QJackCtl, 
you'll see a list of audio devices. You want the one called "USB Audio 
Codec", not the subdevice "USB Audio".

After I start JACK with QJackCtl, I start Audacity. I use Audacity 
because it's much easier to use for simple recording than Ardour, and I 
don't need the power of Ardour for what I do.

Settings in Audacity:
Set your project rate to 48000Hz.

Under Preferences > Device:
Select Host JACK Audio Connection Kit
Playback device: system
Recording device: system
Channels 2: (stereo).

I know you're recording only a single input, but I wonder if part of the 
problem is trying to make the UCA202 operate simultaneously as stereo 
(output) and mono (input). I've recorded vocal input using a mic hooked 
into just one side of a stereo channel, then split the stereo track to 
mono and deleted the empty channel track.

I use JACKD because it's the only reliable way I've found to make my 
audio programs use the USB Audio. If I don't use JACK, all they want to 
use is "Default". On my laptop, Default is the non-functional onboard 
Intel Audio. (Laptop's 8 years old, it's been dropped a couple of times 
and once landed on the corner containing the external audio controls - 
what can I say?)

About monitoring your sax input. The UCA202 has a headphone out jack. 
The switch beside the input channel side turns on or off its built-in 
hardware monitoring. You might try turning hardware monitoring ON and 
plugging your headphones into the headphone out jack instead of using 
software monitoring. See if that meets your needs.

Hope that helps!

gnome at hawaii.rr.com
authenticity, honesty, community

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