Cgs synth

On 12/3/06, Gerald Stevens <logo64@...> wrote:
>
> Hello,
>
> I finally pulled my CGS35 out of the rack and took it to the garage to
> give fixing it one more try. For the most part it works, but the resonance
> has never seemed to give it a nice ringing sound. Looking at a its output
> with a ~1kHz square wave into the LP input and the filter wide open, it
> looks like the overshoot ringing at the top of the step is very high
> frequency (10's of kHz). My question is - how is the resonant frequency
> determined? Which caps and resistors play a role in defining the resonant
> self oscillating frequency? I would prefer to keep this frequency audible.
>
> -gerald
>


[Non-text portions of this message have been removed]

>A follow-up (I like to respond to my own questions ;)
>
>Had another look at the description on Ken's site and pondered it for a
>while, and I "get it" now - the diodes and 2n2 caps filter the sound. The
>2N2222 and 2N2907 pair controls feedback (Q) and hence the resonance. I
>tweaked resistor values a little more and managed to get a little bit of
>"ringing". Problem is, if you turn the resonance pot further, the signal
>amplitude drops dramatically, and the ringing stops. Probably a symptom of
>the Q transistors petering out? About a year ago I tried to replace the
>2N2222 with a higher gain transistor, but this didn't seem to help.
>
>I'll probably just order the latest eurorack version and give it a go
>instead of tormenting my board by swapping components any further.
>
>-gerald
>
>
>
>On 12/3/06, Gerald Stevens <logo64@...> wrote:
>>
>> Hello,
>>
>> I finally pulled my CGS35 out of the rack and took it to the garage to
>> give fixing it one more try. For the most part it works, but the resonance
>> has never seemed to give it a nice ringing sound. Looking at a its output
>> with a ~1kHz square wave into the LP input and the filter wide open, it
>> looks like the overshoot ringing at the top of the step is very high
>> frequency (10's of kHz). My question is - how is the resonant frequency
>> determined? Which caps and resistors play a role in defining the resonant
>> self oscillating frequency? I would prefer to keep this frequency audible.
>>
>> -gerald
>>
>
>
>[Non-text portions of this message have been removed]
>
>
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>
>Yahoo! Groups Links
>
>
>
>