Audio glitch issue when using sample-based instruments in Drambo

EnergyCrushEnergyCrush
in Drambo

Hello all, new here, guys on Loopy forum recommended I post about this issue here and tag @giku.

I'm new to Drambo and had some time over the last weekend to open it up and start digging in. I put together a quick tune and things seemed fine, but as I started to dial in each channel to -18dB, I started to notice that the first kick from Klevgrand OneShot was intermittently louder on different patterns. Sometimes it would be the first step on multiple patterns in a row, sometimes it wouldn't happen for 2-4 patterns, and then suddenly the first kick would be weird again - not just louder, but also sort of flanged.

After asking on the Loopy forum and then doing some testing, this is what I got down to:

First, I'm using just the following gear for this example:

  • iPad Pro 12.9 Gen 3, CPU was generally between 12-15%, RAM around 70%, default buffer size of 512 in Drambo.
  • Sony WH-1000XM4 connected by Bluetooth (usually use Babyface Pro with Beyer 990s, but was learning away from studio for now)


Things checked:

  • The issue happens with just a default instance of Drambo with a single instance of a sample-based instrument like Koala or OneShot. It doesn't happen with Sugarbytes DrumComputer or other synth-based instruments that I can tell.
  • There are no FX or other instruments loaded on any channel or the master, it's super basic.
  • It doesn't happen in AUM when using OneShot or Koala with the same samples driven using another sequencer like Octachron.
  • It also doesn't happen in Drambo if I use Octachron to drive the sample instrument; it only happens when using the Drambo sequencer.
  • It also didn't seem to happen when just playing a single pattern repeatedly, just when there were multiple patterns automatically looping and transitioning across the patterns.
  • It isn't just a specific kick sample, it happens with other samples I loaded into OneShot and Koala as well, but is a little easier to hear with slightly elongated samples like some kicks.
  • It only happens intermittently on the first step of a pattern, never on steps 2-16. It is not consistently a specific pattern. In a loop of 4 patterns for instance, it just intermittently happens on any of the patterns.
  • When the weird flange sound happens, I can see the volume jump inside of OneShot or Koala itself, as if the Drambo sequencer is sending additional MIDI data at the begging of patterns that sometimes causes the sampler to play the sample oddly, but doesn't seem to affect non-sample instruments.
  • MIDI clock or Link are not enabled; everything in Drambo is as default - though in the projects I link below, I disabled incoming MIDI data for Network 1, but this didn't seem to make a difference one way or the other.
  • There are no other programs running or hardware connected to the iPad.
  • When I first encountered the issue, my audio buffer setting was the default of 512. Changing it to 1024 did not make any difference. However, after shutting off the iPad and starting it back up, the problem seemed to disappear completely, with the buffer still at 512. I set the buffer to 256 and after a couple of minutes, the problem starts to happen again. When I change it back to 512 now, it immediately goes away again and doesn't seem to come back. In this was, the problem is at least reproducible on my iPad consistently using the basic example songs I'm linking.
  • A few on Loopy mentioned it may be related to Bluetooth, and that may be true, but I find it odd that this problem only happens in Drambo itself, no other sequencer or audio programs I test with - nor even in Drambo when using another sequencer.
  • Someone was not able to reproduce the issue using an iPad Gen 9, but I did see the benchmarks between these two CPUs is reasonably different. I also don't think they were using Bluetooth when testing.
  • I did try a suggestion from someone to test this with the default iPad audio without Bluetooth, and it seems even running with the buffer at 128 I'm not seeing the same issue after several minutes. In that light, it might very well be related to Bluetooth, but why only when using the Drambo sequencer and not when using Octachron or other sequencers inside Drambo, and why only with sample-based instruments?

This is a link to a compressed file containing basic Koala and OneShot projects that reproduce the issue on my iPad:

https://drive.google.com/file/d/144ai7BpJfSqg1uyVEc55jh2-9PLMHkcR/view?usp=sharing


Would be interesting if something were identified that could resolve the issue, as I'd like at least periodically to be able to write outside of the studio but with headphones so I don't disturb my wife or others around me :)

Thank you very much, and if I can add anything else, please let me know!

Mickey

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