Ambika filter tune

hi there am trying to tune my smr4 mk II filter boards, the instructions say put res at 64 and cutoff at 64 and tune but i get almost no resonance at this cutoff i need to turn it up to 100 to get enough resonance to tune it? any ideas or is this normal.

Did you follow also this order?
Set all oscillators to none,
env2 to 0
lfo2 to 0

For tuning I suggest to use TubeOhm FilterCalib- www.tubeohm.com/demos/FilterCalib.zip
More info in this thread

Maybe this thread helps you?

yep done as instructed in manual but getting no self oscillation at middle c when settings are as above just a low click are there any resistors or capacitors in the circuit that would lower the range of the self oscillation

Yes, you can lower R16. That’s the 18k resistor between C12 and C13. Try 15k.

so which IC is responsible for self oscillation/ resonance

No IC in particular. There is no magical “resonance IC”. Halves of LM13700 and quarters of TL074, fractions of ATmega, and caps, resistors…

im using these MKS-02 1,0N 1uf poly caps from Reichelt (as in BOM) it says they are tolerance ±20% and the rest are 10% could it be this

Hmmm could be… Reichelt used to deliver the 10% version for this reference, that’s why I switched to another part for the Shruthi kits. It’s still surprising though, and you’re the first to report this… Have you tried lowering the value of R16?

yep change to 15k same problem self oscillation bottoms out below middle c the resonance seems too low and should be higher in pitch but cannot get any higher with trimmer has r17 anything to do with the tuning range

Wait wait wait…

When you say the resonance is too low, you mean in amplitude or in frequency?

replaced 1uf caps with 10% ones works perfectly maybe should remove the Reichelt ones so nobody else make the mistake. thanks for your help pichenettes

If these are 1µF caps, this is the wrong part indeed. This should be 1nF. Maybe Reichelt sent you the wrong caps?

sorry just typo i meant 1nf