resonance issue with Steiner VCF

[space_zulu]

Hi everyone, et salut yves

this is my first topic on EM, and i'm having little issue with the yusynth steiner filter :

i have a nice and smooth filtering with each filter (LP, HP, BP, AP), and resonnance seems to work fine i hear the effect it does (and compared it with my microbrute and its pretty close and i'm very glad of it !

but ! the resonance isn't strong enough and i don't have any self-oscillation point, i looked at the schematic but i didn't really get exactly where is the whole resonance circuit and how it works (i just understood that it use IC1b and c in the revised version (http://yusynth.net/Modular/Commun/STEINERVCF/Steiner-improved-sch.gif) )

i run the module on a self made +/-12v PSU and i etched the PCB at home
if anyone had a clew on where to look and/or what to do it would be really helpfull !

thanks a lot

Zulu.

[elmegil]

The resonance is the path through ic1b and ic1c and the resonance pot. If you have a problem causing this, it would be along that part of the schematic.

However, my first suspicion is that using 12V, there is some adjustment needed because this is originally a 15V circuit. I don't have any expertise in this circuit in particular, but I bet some searching around the YuSynth forum here might find something about that.

[space_zulu]

hi and thanks for the reply,

at least i was right for the part of the schematic in cause, that's nice !

but i'm a bit surprised because Yves said that it is possible to run it on 12v without mods that why i posted here,

i'll try to change the gain of the IC1c amp and let you know

[AlanP]

On the schematic, R18 is listed as 3k9 -- with the note at the bottom to change it to adjust the resonance range. Mine runs on 12V (Euro).

Think I might try swapping it out for a 5k or 10k trimmer on my two, just to see what happens. Probably need to -- it's hard on mine to get any self-oscillation that isn't high pitched.

[space_zulu]

that's what i was going to try but i don't understand if it mean the frequency range of the oscillation, or the point of the pot from where the oscillation begin

(i don't know if i make myself clear, but i don't know how to explain it in another way)

[wackelpeter]

i can't remember exactly but i did some modification on R22 and R23... reducing them a bit... just try on one of them hooking another bigger resistor parallel on them to see how it changes so you don't have to desolder everything and can experiment whit it...

[space_zulu]

Problem fixed ! sorry for the late repply, i had to raise R18 a LOT and fix a small short around a condenser.

if someone has the same issue i'm around 30k instead of 3,9k for R18