Moog Opus 3

Moog Opus 3 synthesizer
Moog Opus 3

The Moog Opus 3 was Moog’s only string/ensemble synth. Today it is the perfect choice for you if you want string synth limitations at a Moog price. I think the organ sound is better than average, the string sound is a little worse, and a typical Moog filter on the “brass” section makes it at least better than the average string synth’s brass/synth tone. However, the single envelope on the brass section and its single-triggering behavior mean you can’t really accompany yourself with string or organ sounds while taking advantage of the envelope on the brass/synth section.

This had a pretty standard handful of issues: bad divider ICs (TDA 1008 in this case) which is a ubiquitous issue among all synths that use them, and the sticky, dirty sliders and switches and cold solder joints on connectors and controls that I always see in Moogs from this era.  I cleaned things up pretty quickly, but then the spontaneous failure of a diode in the bridge rectifier instantly destroyed the 12V regulator and with it, the M083 top octave generator. Agh! This is the most expensive part in the whole thing. They go for about $60 NOS, but fortunately you can get a cloned replacement from Flatkeys for only about $30, which I’d bet on against a 35 year old chip anyway. The people who run Flatkeys are heroes. They make so many versions of TOG/TOS chips for every old synth and IC-era organ, and my guess is that they’re not in it to get rich.

Maybe this is obvious but if one rectifier diode in a synth fails, you should replace the others too! But I actually recommend preemptively replacing all rectifier diodes in every old synth with a discrete diode bridge– I have seen spontaneous failures like this several times and I should have just done it right away.

Anyway, that sucked but the synth is working great now and I really like the design from a visual standpoint! I love these color-topped knobs and slider caps.


2 thoughts on “Moog Opus 3”

  1. I know absolutely nothing about synths or where to start. Recently aquired an Opus 3 and I’m not having any luck getting a single sound out of it. The power light is blinking very slowly. Any ideas on where to start?


    1. Hi James… unfortunately, as much as I think it’s cool for people to learn to fix things themselves, I can’t begin to explain to you how to try to fix this if you’re an absolute beginner. I’d have to advise you to seek help from a professional on this one!

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