Ultra fast lfo mod for the Opus 3

[dancelwerk]

I was looking the modulation section and I made a mod to get a very fast lfo, adding a capacitor of less value together to C10 in parallel, you only have to put together negative legs of capacitors soldered, the positive leg of each capacitor is redirected to a SPDT, and the common, the center pin is wired to the boards, where was the positive leg of C10, and when you want you have the original lfo or the ultrafast lfo. You can get a more extreme speeds or very slow rates, increasing or decreasing the value of capacitor. It's very easy to do!!!

if you do this mod is by your own risk, you know, but you get a different character and new sounds of your Opus3.

And now i want a CV in to the filter.

I hope to get it.

Fernando.

[EMwhite]

That's great! I'm going to restore/mod my Opus 3 at some point. CZ Rider has many mods to his (which I think he did himself)

I know enough about electronics to get myself in trouble. I can transcribe a mid-sized schematic to board and design rudimentary mods that I instal at my own risk all the time The great thing about these old synths is the absence of custom ICs, the generous component spacing (often with single sided boards) and readily available components. Be wary of the chips within the Chorus section, however as I understand they are rare and NLA.

If anybody has anything to contribute to this thread, please share!

[dancelwerk]

A picture of the mod

i can't upload the picture, is under the limit of the size, but doesn't works, sorry

[Kevin Lightner]

One suggestion regarding LFO mods (and I've done a *lot* of them.)

Using a FET input opamp instead of the standard types used can allow very wide ranges to be obtained.
Simply put, a FET type opamp presents less of a load for the cap and usually far faster rise times.
This means one can obtain a slow range in minutes per cycle and a fast range in the khz range (FM type modulation.)
One still substitutes capacitors via a switch, however you might want to use caps with different properties.
(ie: tantalum or polystyrene, which are very different from each other.)

Also, understand that the amplitude and waveform shapes can change when you do such mods.
For example, on one mod I limited the top speed to about 5Khz because past that, the amplitude started decreasing.
And on slower speeds, waveform skewing might occur.
That is, a triangle wave might start to appear more like a sawtooth where the ratio of charging vs discharging is no longer equal.

A scope and freq counter can help.

[dancelwerk]

Thanks Kevin i check your suggestion, I keep you informed.

Fernando.

[Vsyevolod]

Kevin quite the group a few days ago. You'll have to contact him at his email address.

Stephen




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