The usual trick is to use OTAs instead of the op-amps to vary the frequency,
and as OTAs don't use the same physical or electrical configuration, it
would get ugly. Now if you are simply wanting to do the triple resonant
filter and don't care about accurate tracking, some possibilities do open
up. Basically, you replace the dual 100k pot with a pair of vactrols in
parallel with a couple of fixed 100k resistors. The current through the LEDs
will now control the frequency.
Ken
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
and as OTAs don't use the same physical or electrical configuration, it
would get ugly. Now if you are simply wanting to do the triple resonant
filter and don't care about accurate tracking, some possibilities do open
up. Basically, you replace the dual 100k pot with a pair of vactrols in
parallel with a couple of fixed 100k resistors. The current through the LEDs
will now control the frequency.
Ken
>Yep, they're definately terms that a newbie can understand..._______________________________________________________________________
>I got the idea after looking at the Doepfer A127 triple resonant
>filter. I'm not interested in the in-built LFOs, but I like the idea of
>being able to VC the freqs (talking synths). Is there a technical
>reason why the CGS30 isn't suitable for VC? (jut out of curiosity,
>Ken, I'll assume you know what you're talking about ; )
>
>Many thanks
>
>Stuadh
>
>
>
>
>--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
>> I'd suggest building a different sort of filter if you want voltage
>control.
>> It's kind of like asking how to add wheels to your motorbike
>because you
>> want a car.
>>
>> Ken
>>
>> >Hi list,
>> >
>> > I'm about to start building a 3 x band Pass filter + DC mixer
>as
>> >shown on the website.
>> >
>> > However, can anyone explain (in terms that a newbie might
>> >understand) how to add voltage control to the frequency of the
>BP
>> >filter. I'd like each channel to have this in addition to the
>manual
>> >control.
>> >
>> >Yours Aye
>> >
>> >Stuadh
>> >
>> >
>> >
>> >
>> >
>> >
>> >See the following URLS for the CGS Modular Synth home
>page:
>> >Main: http://www.cgs.synth.net/
>> >Secondary: http://otherunicorn.0catch.com/synth/
>> >Yahoo! Groups Links
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>>
>__________________________________________________
>_____________________
>> Ken Stone sasami@h... or sasami@c...
>> Modular Synth PCBs for sale
><http://www.blaze.net.au/~sasami/synth/>
>> Australian Miniature Horses & Ponies
><http://www.blaze.net.au/~sasami/>
>
>
>
>
>
>
>See the following URLS for the CGS Modular Synth home page:
>Main: http://www.cgs.synth.net/
>Secondary: http://otherunicorn.0catch.com/synth/
>Yahoo! Groups Links
>
>
>
>
>
>
>
>
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>