Strange Pitch Drift After Warm-Up on Minimoog – Anyone Else?

[bettylim]

Hey everyone,

I’ve noticed something odd with my Minimoog recently. After powering it on and letting it warm up for about 15–20 minutes, the pitch on all oscillators begins to drift slightly, even though the tuning knob remains untouched. It’s subtle, but enough to cause it to go out of tune during a recording session.

I’ve tried different power outlets, checked the room temperature, and even avoided using it near other electronics that might cause interference. Still happens.

Has anyone else run into this? Could it be aging components, or is there a simple calibration trick I’m missing? I’d love to hear if others have experienced this and how you fixed it.

[VCO]

I have a Moog Voyager that pitch drifts. I tune all three oscillators. It stays in tune as long as I stay on the current preset but as soon as I change to another preset it’s out of tune as needs to be retuned again.

[VCO]

I haven’t fixed it. I read it could be out of spec capacitor that causes it to drift. Unfortunately Moog doesn’t service the Voyager anymore.

[analogmonster]

The exponentiator section of a VCO is responsible for pitch drifts. The exponentiator converts a linear voltage (CV) into an exponential current within a VCO's core for human ears.

AFAIK the Minimoog used three different variants of exponentiators for the VCOs over the years: A discrete transistor pair variant which is not temprature stabilized at all, a 3046 transistor array variant which can be used with a tempco resistor or with a heater circuitry, or a 726 based heated transistor pair. As I don't know whether the Mini used the 3046 with a tempco resistor instead of a heater circuitry around only the 726 variant is guaranteed as heater solution.

And only the heater variants ensure temperature stability over a longer time. I build my own VCOs with a 3046 transistor array based expo with heater circuitry only. They are let's say "online" after 30 seconds and stay stable after that time.

So it depends on your Minimoog model version whether temperature stability can be achived or not.

[RL]

Hi,
is the pitch wheel ok?