[LAU] Distorted sound

David Sumbler david at aeolia.co.uk
Fri Dec 11 16:03:48 CET 2020

On Wed, 09 Dec 2020 16:25:33 +0000 David Sumbler <david at aeolia.co.uk> wrote:

> I am running Qtractor and QJackCtl on a Raspberry Pi 3B+, with sound
> output through the headphone jack.
> When I play a wav file using 'aplay' it sounds fine, but if I load it
> into a track in Qtractor, it is very distorted.  A female voice
> sounds like basso profundo (although the speed is correct) and is
> very distorted.  It looks to me as if this is probably because the
> output of Qtractor is not being directed through jackd.

Thank you for the various responses to my query.  To answer Rui's
question first: the binary I am using is from the Raspian repository,
and is version 0.9.5.

The discrepancy between what QJackCtl and QTractor are showing in their
respective connections windows fortunately seems to have largely
disappeared for some reason unknown to me, and clearly the signal is
being directed from Qtractor through Jack.

As regards the distorted sound, I thought it might be useful to direct
the sound through HDMI (although this is not what I want to do
ultimately) to see if the same thing happens.  It has taken me hours of
fiddling around with settings to achieve this, but finally I succeeded.
The same .wav file that I played in Qtractor and which was badly
distorted through headphones, sounds absolutely fine through an HDMI

After much experimentation with settings, I have now got the sound from
Qtractor back to the headphones.  The distortion is still there.  I
would be tempted to think it might be a fault with my Raspberry Pi, but
the sound is fine when using 'aplay', so clearly the sound system on
the Pi is fundamentally OK.

Comparing the settings in QJackCtl in the Parameters and Advanced tabs,
they are the essentially the same both on the Pi and on my HP laptop
running Ubuntu 18.04.

I'm stumped.


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