Reverb sounds wrong at sample rates above 48000

[kjyv]

Expected behavior

Clean reverb sound

Actual behavior

Reverb sounds like a metal bucket, saw like. Or a bit like a resonating snare drum in a loud band rehearsal.

Information

• Which version of amsynth are you using?
  current git / 1.6.4 from ubuntu repositories
• Which build of amsynth are you using? (stand-alone application, LV2, DSSI, VST)
  LV2, standalone
• If using amsynth as a plugin, which host application are you using?
  Qtractor, any
• Which operating system & version are you using?
  Debian / Ubuntu

I've tried compiling with different optimization flags, with/without fast-math, but it does not change the sound.

[kjyv]

I've noticed that helm (https://github.com/mtytel/helm) uses pretty much the same reverb model based on freeverb but not the same code. And it sounds good, on the same box.

[tyrumus]

Just stumbled on this repo, and it looks like amsynth's current version is 1.8.0, and you're using version 1.6.4. Have you tried the latest version?

[kjyv]

I guess I should have written current git AND 1.6.4 instead of the /. I only mentionend this to illustrate that the issue also happens on a distribution package, not just on my specific compilation.

[nickdowell]

@kjyv what sample rate is amsynth running at?

It would be helpful if you could provide a recording of the output (preferably with one of the built-in preset sounds) that demonstrates the issue 😃

[nickdowell]

This is fixed now!

[kjyv]

Great! Haven't gotten around yet to provide you with recordings, but I'll look into it again. Cool that you found a fix, but to be honest I think I used 44100 Hz. I'll check the commit in any case.

[nickdowell]

Prior to the fix, the reverb sounded really bad at 192 kHz.

Didn't have a 192 capable card when amsynth was first developed so it had never been tested!

[kjyv]

So, sorry took me a bit to get back to this...
It's nice that you fixed a problem at higher sample rates but this is not the problem for which I created the issue. I think a simple case to reproduce this (at 44100 Hz) is to use the basic sine sound sound you get after starting amsynth and turn up reverb wet, reverb width and reverb stereo all the way and then compare the reverb sound between different reverb damping values. New high frequencies are added the lower damping gets. Maybe this is the meaning of damping for this reverb algorithm but it sounds bad (=scratchy, distorted) also with damping all the way up. Other software reverb effects don't do this, e.g. as mentioned helm.