[ubuntu-studio-users] Questions about production

Ralf Mardorf ralf.mardorf at alice-dsl.net
Sun Jul 27 08:33:26 UTC 2014

On Sun, 2014-07-27 at 13:07 +0530, Shubham Mishra wrote:
> 1. I seem to be running into xruns a lot

CPU frequency scaling is the first one under suspicion, so run

$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

Assumed the output shouldn't be "performance" for all CPUs, then run

$ echo -n performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor >/dev/null

> 2. Is it ok to use rakarrack effects while recording or should I monitor 
> just a clean signal and then apply effects later?

That depends on what you want to get and to the horsepower of your
machine. It can't harm to use rakarrack, to play with the wanted sound,
but at the same time to record the clean signal, so you could fine tune
the used effect late.

> Same with zynaddsubfx; should I use that while recording? I read
> somewhere that apparently it is not real time safe.

Use it while you're playing, not only for recording. It is rt safe, what
ever that should mean. Consider to use yoshimi, it's the successor. By
the preferences of both synth, you can select the sound quality, less
good sound quality, less DSP load.

> 3.  For monitoring while recording, is it better to route the midi 
> signal through qtractor to the synth or to connect the keyboard directly 
> to the synth?

Rout it through qtractor, there's no need to double connect to the

> 4. On an unrelated note, how do sfz files work? Are they sort of like 
> sf2 files, which I can just load up on Qsynth or something?

I don't know, but perhaps linuxsampler can use those files. Qsynth is
the frontend for fluidsynth. I guess fluidsynth can't handle thsoe
files. Qsampler is one of the frontends for linuxsample. Perhaps there's
a PPA providing linuxsampler or maybe the KXstudio repositories provide
it. Debian and Ubuntu unlikely will provide it, regarding to a licence


Start learning to compile it on your own ;).

> 5. For the microphone, is it ok get a USB microphone? I heard that it's 
> messy handling multiple sound cards with jack. If yes, then what is the 
> best way to connect a microphone?

Assumed your sound device has got a microphone input, then better use
this one. Btw. please give more information about your hardware. CPU,
RAM, sound devices.

Post the output of

$ aplay -l
$ arecord -l

If possible don't use USB MIDI, it has got the tendency to increase MIDI
jitter, IOW the timing might become audible less good, OTOH if you
quantise using a sequencer, this might be unimportant. The best thing is
to use PCI(e) MIDI, or use parallel port MIDI, usually only available by old PCs.

For MIDI out from the computer to external synth, never ever use USB,
since than the quantisation can't fix the jitter, only the other way,
keyboard to computer could be usable, but also could cause trouble.

For using external MIDI synth, I recommend to use a kernel-rt instead of
the lowlatency kernel.


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