# Moog Opus 3
“Up for bid is a Moog Opus-3. If you’re not familiar with the Opus, it’s basically Moog Music’s version of an ‘orchestra’ synthesizer, having separate String, Brass, and Organ sections. It uses divide-down technology, which makes it basically ‘allophonic’ in that all keys can be simultaneously played. There’s a classic Moog filter which the Brass and Organ sections can be run through, and an analog Chorus section which the Strings and Organ can be run through. There’s also a triangle LFO for modulation of the oscillators or the filter, a pitch wheel, and an ‘articulator’ (basically the output VCA).
All keys, sliders, and switches work cleanly and clearly. There is a bit of scratchiness in the main volume pot, but it seems to get less the more I work it; the other pots are clear. I’ve checked out all the functions and everything works correctly per the Field Walkthrough in the Service Manual.
I’ve performed the following maintenance/improvements:
* Cleaned out the horrible foam that destroys the sliders
* Replaced all the sliders and switches with new ones from Technology Transplant (a $150 value, just for the parts)
* Recapped the electrolytics on the panel board and the power supply
I’ve also made several modifications to this unit; most of these are very basic but very useful:
* Expanded the range of the LFO, from very slow (~ 0.1Hz) to audio range (>30 Hz)
* Added an audio input to the VCF
* Added an audio input to the Chorus circuit
* Added a ‘GATE IN’ jack (triggerable by voltage > 2V)
* Replaced the slider caps with Arp-like, color-coded rubber nips (I still have all the old slider caps, and I’ll include them with the shipped unit)
I’ve always thought that the Opus had one of the better implementations of the Moog filter and this unit allows an external input to be run through it while being triggered from an external gate. Feeding a sound into the analog Chorus can certainly add richness and shimmer. And, credit where credit is due: the modifications that I’ve made were inspired by a Moog Opus-3 that was ebay’ed several years ago by a well-known Moog synth technician. Note that he did not make the modifications to this unit – I did – but he should get credit for the ideas!
Now for the bad news. There’s a cosmetic flaw in that the front panel sticker on this unit is fraying in the upper corners (see the pictures). It’s not a progressing problem, as it’s been like that since I got the unit 4 years ago and it never bothered me.
The Owner’s and Service Manuals are available freely on the web. I will include an IEC power cord with the synth” Link