Moog (Realistic) Concertmate MG1 "Bell Tone" is a Ring-Mod Effect?


Staff member
Nov 2, 2017
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I have successfully brought my Moog MG1 back from the dead after repairing the common black goop problem from the old internal disintegrated foam. As well, I have replaced all the sliders with a new set purchased on Ebay. My question is this: The Bell Tone slider is supposedly a ring modulator effect. My Bell Tone slider doesn't really impart what I would describe as a classic ring mod sound. I'm curious if others have experienced this as well, or is it more likely my MG1 is not functioning properly and I need to replace some parts to get the Bell Tone slider to sound closer to a real ring modulator effect?

Monkey Man

VIP Supporting Member
Dec 19, 2017
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From KLeonard's site:

Major Features

31 note keyboard (F to C)
Monophonic, using a really bad organ sound to achieve "polyphony" (which, fortunately can be shut off at the Mixer)
Two tone sources / oscillators, square and saw waves
Oscillators can be synced or detuned
Pink noise generator
Bell tone generator (ring modulator)
A countour generator (basically attack/release, with a switchable sustain)
External ports for trigger and pitch
A whopping 50dB signal to noise ratio!
User's guide, service manual (service manual covers the principles of operation in detail, basic repair, tune up, schematics, parts lists, etc)

MG-1 - Lots of great info on this page that may help with your "restoration" efforts, RM.

Just to be certain the signal path to the slider is what it should be, check out what he said way down at the bottom of the page:

"But then I discovered that the "bell tone" (ring modulator) was not working. Eventually I traced it back to the yellow wire going from the lower PC board to the upper one--it had been cut! Someone modified this synth to take the TAPE IN and run it through the Bell Tone slider, probably using it as a volume control to allow external sound to be processed by the filter."

According to Wikipedia:

The MG-1 includes:
Moog Concertmate MG-1 - Wikipedia

So, it's definitely AM, and hopefully it helps that Wiki specified it as being of VCO 1 & 2.