Does anyone always hear something like “unwanted distortion” when turn the main volume’s knob ?
never heard of that one. Is it a crackly sound? That sound is more common for pots.
Yes Veets, absolutely it’s a “crackly sound”…
Crackly pots are often caused by one of two things. A failing or “crap” solder joint is one - resolder the joints to fix this. The other one is a dirty pot and this can happen more quickly if your machine is around a lot of smoke, dirt or dust. A lot of people will say that spraying De-Oxit (or something like that) into the interior of the pot fixed this kind of problem. You can do a web search for DeOxit and pot to learn more about this. Or go over to Gearslutz.com and type Deoxit in to see more about it being used with music gear.
If your machine is under warranty, you can send it in. If not, any technician can do these things and you can probably do it yourself too. But it would void your warranty if you still have one and Elektron does not fix it.
Good luck.