VCF offset trimmers?

Hi all,

the fact thatI I lurve my Ambikas goes without saying. I have two of them, SMR4 and SVF. The only thing that irks me a bit about them is that on the stock voice cards, there’s no way to get the filters of different voice cards in tune with each other – the scale is adjustable but not the offset. So you cannot play proper chords with a self-resonating filter patch. The TubeOhm SMR4-Plus version has this, and it would be a great great addition indeed.

From the schematics, it looks like it’s as simple as putting a 50k trimpot between VRef and the TL074 pin… is this correct? If so, it’s an easy fix.

Regards
Björn

Yes, this is correct.

Would love to see this mod documented further here!

Out of interest, where would one put the trimmer on an SMRmkII? The resonance on mine actually falls very neatly on the quartertones in between the semitones. Of course it locks onto harmonics of the oscillators, but it would be nice to get the resonance by itself to be in tune.

I would probably just add two cables (Vref > pot and pot> TL074) and hot-glue the trimmer onto the PCB. Will try the mod and post about it here… maybe this weekend, if I have a 50k trimpot lying around.

@pichenettes, out of interest – why did you leave the trimpot out? On a poly, it makes a lot of sense to have it.