Multimoog Ground Loop Tuning Issue

[Monkhiggins]

I recently purchased a fully serviced Multimoog from a local repair shop. Upon setting it up at my home studio I began noticing drastic tuning issues that would come and go. I’m not talking a slight drift but rather notes moving 3-4 steps. I began doing multiple tests and plugged in the multimoog to the same outlet as a guitar amp and had ALL of my other gear + lights off. The multimoog was absolutely perfect. However the second I turn on any lights, or other keyboards, racks etc, the tuning goes crazy. Keep in mind I live in a fourplex that was built in the 1920’s. What are my options to be able to use this thing while my other gear is on? I purchased a little ground lift adapter to go from 3 prong to 2 prong however I’m scared to use it for fear of damaging the multimoog or electrocuting myself. Would this be safe to use? Are there any other options? Any advice would be greatly appreciated!

[till]

Ground loops create an audible buzz at 60 or 50 Hz (depends on mains system). I never ever heard about this causing a bad tuning on analog synths. For a steady pitch, you need to have a well defined constant voltage at the VCO. And so my guess is a faulty PSU of your Moog or a massive voltage fluctuation in you mains when you use more power.

If you have no experience with electronics, ask for help by a experienced person.

And if a synth got a three prong mains connector, better do not use a ground lift. There is a good reason why there is a ground.

[analogmonster]

Yes, that is true. But perhaps the ground RAIL is polluted. This can happen if you have a poor or highly impedanced ground connection in conjunction with a Moog synthesizer. The S-TRIGGER of Moog Synths can cause this for instance, as the the shortening of an envelope gate connector (S-TRIG) to ground can pollute the ground with offset voltages.
And without a clean ground reference or a random voltage offset on the ground rail all VCOs change tune for instance.