The unapologetically boring-looking Quasimidi Polymorph is a very powerful VA polysynth from the early 2000s that allows you to sequence and play back 4 parts on 4 different synth sounds, recording and playing back all the parameter edits you make along the way, and send them out on 4 individual outputs. So basically it is 4 sequencing polysynths in one.
Unfortunately it suffers from the same terrible “knob jitter” problem as many, many other pieces of gear that were made in the late 90s and early 2000s, but with 43 potentiometers, it’s just about as bad as it could possibly be.
A lot of gear made around this time used poor-quality, normal analog rotary pots encoded into digital increment/decrement data for all their controls. Unfortunately, as these pots get dirty, they start to send out a constant stream of arbitrary digital (usually MIDI) values, meaning all your settings just constantly jump around. The problem will inevitably spread to all the pots on the unit and cannot be solved by cleaning them. This happens with endless digital encoders too.
This one really did have all 43 of its pots jittering. The only solution is to replace them all.
Service Tips: The pots in here are 10K linear taper with side tabs to snap into the board. It is tedious to find the right ones on an online catalog, as you have to make sure that the measurements of all dimensions of the pot are correct, and since I already went through that I don’t mind telling you what they are. If you are comfortable desoldering 43 pots, go for it.
The ideal replacement is TT Electronics P120PK-Y25BR10K, which is listed on both Digikey and Mouser but currently backordered on both. Hopefully it is not going out of production. Fortunately, my client found some on Ebay.
Bourns PDB12-M4251-103BF also has the same value and dimensions, but has a D shaft; I believe it should work, but I can’t promise that the knobs would fit.
If you are experiencing this problem with any of your gear, feel free to inquire whether we can fix it for you– it may not always be worth the cost and parts that fit may not always be available, but I’m always willing to take a look.
Meanwhile, I am preparing to replace all of the pots and encoders on my own Korg Electribe ESX-1 🙁