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barely any sound from Bristol synth

I am new to jack and am trying to use qjackctl to get sound from the synth emulator Bristol on a Raspberry Pi 4B.

I installed Bristol on a Raspberry Pi 4B and installed qjackctl. I can start Bristol without any issues (for instance `startBristol -mini -midi alsa`). I can also start `qjackctl &` and connect a midi input to Bristol, and Bristol's outputs to system->playback_1 and system->playback_2 using theqjackctl Graph GUI. I am using the headphone jack on the RPi 4B. Once I make these connections, I can hear a little bit of audio when I play notes on the Bristol gui or with the midi controller. But, the audio is barely audible and very messed up in a way that is hard to describe: When I play a note, I mostly hear some quiet high-pitched crackling, a very high-pitched (12 kHz?) whine, a little bit of the emulated sound, and no low-pitched sound.

I recorded the sound coming out of my headphones with an iphone and attached the file. You can mostly here me using my mouse, but you can also hear the soft sounds coming from my headphones.

I know that the sound / headphone jack is working in general, because I can play an mp3 file on the RPi and it sounds normal on the headphones. So, the issue has something to do with Bristol or the Bristol-qjackctl connection.

Things I tried:
Because I thought I might have a sample rate issue, I tried changing sample rate settings in Bristol or in qjackctl, but this did not change the behavior

Because I thought I might have a gain mismatch, I lowered the output of Bristol with -outgain 1 which also did not help

I also tried changing every setting available in qjackctl's Setup menu to see the effects, but nothing was helpful.

Thanks for any help

rncbc's picture

hi, this is a general bristol issue, more like a feature: output volume is historically low;

please refer to the bristol documentaion or issue tracker if either is still alive :)

i'll repeat: it is neither a JACK or ALSA issue: most probably you'll have to insert an amplifier plugin or other jack application between bristol outputs and the system playback ports; qjackctl can only help in inter-connecting the ports; it has no role on the signal gain or volume whatsoever. sorry


This is not just a gain issue, the audio is completely messed up (see my original description)

rncbc's picture

ok, then for the "messed audio" issue you better check if any other jack applications, anyother but bristol, do have the same symptoms; if they have, then review check your jackd settings (sample-rate, buffer-size, number of periods, number of channels, etc.); one suggestion woul be to have a playback-only setup; if not, the the problem resides in the bristol suite for sure and there I can't help you any further. sorry.


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