Crackles in audio

I’ve got zynthian working on a pi3b+. I’m in awe of its brilliance! One problem I have though is crackles in the audio. Looks like the system is dropping audio frames or something? This is with just one synth layer. Applies on zynaddsubfx and likewise aeolus. It is not the audio cable or amp as they work fine on other sound sources. I read people have similar with pianoteq and lowering the audio quality helps? Any hints appreciated. Also is there some place people share nice presets?

What are you using as sound interface ? The RPI internal one or some kind of external DAC ?
What are your jackd parameters ?
Do you have a descent power supply and a good cable ?

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Official Pi PSU. Jackd settings are default. Raspberry Pi 3 Model B Rev 1.2
Soundcard: HifiBerry DAC+ ADC PRO

Your hardware and software settings seems okay from my point of view. Maybe the 7 inch touch screen could be power hungry. Do you have any red lightning notification on the screen (wich means underpower) ?
Xruns (who make crackles) are notified as red triangles.

Have a look here for modifying jackd parameters :
Hifiberry Digi + Pro at 96khz with x-runs

Interesting… I tried replacing all the power cables to both screen and pi and that has definitely helped. I am still seeing the xrun triangles so will mess with those settings tomorrow. I got so far as having a Salamandar Piano, DX7 and a zynaddsubfx pad playing together with reverb. I’m very pleased. Could buy a pi4 if its needed. I also discovered my touchscreen is rev 1.0 hardware which is indeed very power hungry and has no brightness setting:(

Yep, sounds like power supply issues. The Raspberry Pi is very sensitive to poor supply including poor interconnects which increase resistance reducing available power. Three engines running on a Pi3 sounds okay. Add effects and you may be starting to push its resources, especially if you still have some power issues, e.g. excessive current drain (the screen, attached USB devices, etc.) or suboptimal cables / connectors. Good to hear things have improved.

So all sorted now. I hadn’t realised I was running a pi 3b. I had a 3b+ I use for something else so swapped that in. Still x-runs but a few less. Now I’ve upped the buffer to 512. I think I can ‘feel’ the latency but its bearable for now and the sound is perfect… I do like the idea of getting the full kit with a pi4 at some point but I’m more in a hurry to play with the sounds than the electronics for now. It’s so much fun!