Resonance boosting combinations ?

[sash]

hello everybody,

the mods I've done to boost resonance is this combination :

R97 : 8.2 k instead of 10 k
R109 : 22 k instead of 10 k

as said in the official x0xb0x mods (I put 8.2 k, not 7.5 k as adviced)

But the resonance is already whistling at 3 o'clock, so it's too "early". For me the resonance has to whistle ( = auto-oscillate) at the very maximum only, that's to say 5 or 6 o' clock.

(Should I say that i have very high beta 2SA733P (330 to 350) at Q8, Q9 and Q10 ? )

So have to reduce this mod, because the resonance is too much boosted.
I think of replacing R97 with 9,75 k (1% resistor) and R109 with 12 or 13 k. So the change would be much more "subtle". And I'll maybe have an auto-oscillation only at the very maximum resonance only.

I don't know if it's 8.2k at R97 or 22k at R109 which is the most responsible for this "overboost"...

I read a topic here of a guy who put a potentiometer attached to R97 to vary it from 9 k to 9,5 k. But I don't know what value he has for R109... Maybe he let the original 10k ?

Has somebody an experience with the combination R109 - R97 mod ?

[E:pp:ik]

Hi sash

I only changed R97 to a fixed value of 9.2k and that was enough to give me that boost from about 90% of the RES pot. It was enough for me. I didn't see a point in putting an additional pot in. I also never needed to adjust R109.

[antto]

yeah, i also just modified R97, nothing else
i put a 10K pot there but that's because i'm doing analysis for my soft synth and sometimes i need 0K resistance (don't ask why)
but the perfect value for R97 for me is about 8.9 to 9.1K for general use

[sash]

but the perfect value for R97 for me is about 8.9 to 9.1K for general use

So ok, I'll replace R109 with the original 10k.

And for R97 with 9k resistor, how does your resonance behave ?
Does is go to full whistling auto-oscillation (which is'nt TB-303ish ) ?

I was thinking just to add a little boosting on the resonance and using a 9.75 k, but maybe it's too subtle. Perhaps 9.5 k is a good choice if I want to stay close to the original 303 sound.

[antto]

here, i set my pot to 9K (measured it with my nasty meter)
R97_9K.rar (6.1MB/wav)
first i play a silly pattern with the resonance at 3'o'clock
then i transpose it up a little, turn the resonance all the way up and bring accents
then i switch to another pattern and square wave

for a "sane" 303 sound i'd suggest somewhere from 8.9 (kinda josh-wink-ish) to 9.4K (fair) but the sweet spot for me is about 9 - 9.1K
my original resistor was 9.97K (measured with the same nasty meter) and it wasn't enough..

[sash]

here, i set my pot to 9K (measured it with my nasty meter)
R97_9K.rar (6.1MB/wav)
first i play a silly pattern with the resonance at 3'o'clock
then i transpose it up a little, turn the resonance all the way up and bring accents
then i switch to another pattern and square wave

for a "sane" 303 sound i'd suggest somewhere from 8.9 (kinda josh-wink-ish) to 9.4K (fair) but the sweet spot for me is about 9 - 9.1K
my original resistor was 9.97K (measured with the same nasty meter) and it wasn't enough..

what a nice "acid track" you did, the maximum resonance is just perfect !
I have 1% precision resistor here which indicates 9,16 k, so I'll put it at R97.
Thanks !

[E:pp:ik]

Check my blog at the link below. I posted a video back in the November 2009 where you can hear an original 303 and mine back to back with that resistor tweak.