Cgs synth

>Hi Ken
>
>If I wanted to use a series of your bandpass filter boards to build a
>fixed filter bank, how would you suggest I replace the dual Freq pots
>with resistors for best affect? Something similar to the DotCom fixed
>filter bank (http://www.synthesizers.com/q127.html) with bandwidth
>controls and individual band outputs. (I'm toying with the idea of
>building a patchable vocoder. Simple VCA's are available, I just need
>to find a small, simple envelope follower...)
>
>Larry T.
>
>
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>
>Yahoo! Groups Links
>
>
>
>

>
> On 6/2/07, Larry T. put forth:
> >I just need to find a small, simple envelope follower...)
>
> You can just wrap a full-rectifier around an op-amp followed by a
> one-pole LPF (a cap going to ground). There are numerous examples of
> various effects containing this sub-circuit on the web.
>
> You might find this article interesting:
>
> http://www.geofex.com/Article_Folders/noteproc/noteproc.htm
> <http://www.geofex.com/Article_Folders/noteproc/noteproc.htm>
>
>

>Hi,
>
>On the subject of the band pass filter, I was looking at this circuit
>today and was wondering if it could be powered from a single supply? I
>assume the + op amp inputs could be connected to a voltage reference of
>half the supply (using two equal value resistors) but what about the
>other ground points such as the 4.7k and 15k resistors?
>
>James
>
>Mark wrote:
>>
>> On 6/2/07, Larry T. put forth:
>> >I just need to find a small, simple envelope follower...)
>>
>> You can just wrap a full-rectifier around an op-amp followed by a
>> one-pole LPF (a cap going to ground). There are numerous examples of
>> various effects containing this sub-circuit on the web.
>>
>> You might find this article interesting:
>>
>> http://www.geofex.com/Article_Folders/noteproc/noteproc.htm
>> <http://www.geofex.com/Article_Folders/noteproc/noteproc.htm>
>>
>>
>
>
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>
>Yahoo! Groups Links
>
>
>
>

--- In cgs_synth@yahoogroups.com, sasami@... wrote:
>
> Use pairs of 100k trimmers, NOT physically attached. That way you
can adjust
> both the position and the width of the band. You could get a couple of
> envelope followers per NE571 if you don't mind the price.
>
> Ken
>
> >Hi Ken
> >
> >If I wanted to use a series of your bandpass filter boards to build a
> >fixed filter bank, how would you suggest I replace the dual Freq pots
> >with resistors for best affect? Something similar to the DotCom fixed
> >filter bank (http://www.synthesizers.com/q127.html) with bandwidth
> >controls and individual band outputs. (I'm toying with the idea of
> >building a patchable vocoder. Simple VCA's are available, I just need
> >to find a small, simple envelope follower...)
> >
> >Larry T.
> >
> >
> >
> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> >
> >Yahoo! Groups Links
> >
> >
> >
> >
> _______________________________________________________________________
> Ken Stone sasami@...
> Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>

>Ken, thanks for the feedback on the bandpass filter boards.
>
>As for the NE571 (Philips SA571 too it appears), do you have a circuit
>in mind? The price does not seem unreasonable for 2 followers if it
>uses as few external parts as I suspect. But I'm not much at design.
> OTOH, I can do breadboards and PC board assembly pretty well.
>(Jameco has NE571's, and a lot of companies have SA571's.)
>
>Thanks to Mark as well for the noteproc link.
>
>Larry T.
>
>
>--- In cgs_synth@yahoogroups.com, sasami@... wrote:
>>
>> Use pairs of 100k trimmers, NOT physically attached. That way you
>can adjust
>> both the position and the width of the band. You could get a couple of
>> envelope followers per NE571 if you don't mind the price.
>>
>> Ken
>>
>> >Hi Ken
>> >
>> >If I wanted to use a series of your bandpass filter boards to build a
>> >fixed filter bank, how would you suggest I replace the dual Freq pots
>> >with resistors for best affect? Something similar to the DotCom fixed
>> >filter bank (http://www.synthesizers.com/q127.html) with bandwidth
>> >controls and individual band outputs. (I'm toying with the idea of
>> >building a patchable vocoder. Simple VCA's are available, I just need
>> >to find a small, simple envelope follower...)
>> >
>> >Larry T.
>> >
>> >
>> >
>> >The CGS Modular Synth home page: http://www.cgs.synth.net/
>> >
>> >Yahoo! Groups Links
>> >
>> >
>> >
>> >
>> _______________________________________________________________________
>> Ken Stone sasami@...
>> Modular Synth PCBs for sale <http://www.cgs.synth.net/>
>> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>>
>
>
>
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>
>Yahoo! Groups Links
>
>
>
>

>
> Hang some electros across your new voltage divider reference to
> decouple it,
> and use that as your "ground" for the other components.
>
> >Hi,
> >
> >On the subject of the band pass filter, I was looking at this circuit
> >today and was wondering if it could be powered from a single supply? I
> >assume the + op amp inputs could be connected to a voltage reference of
> >half the supply (using two equal value resistors) but what about the
> >other ground points such as the 4.7k and 15k resistors?
> >
> >James
> >
> >Mark wrote:
> >>
> >> On 6/2/07, Larry T. put forth:
> >> >I just need to find a small, simple envelope follower...)
> >>
> >> You can just wrap a full-rectifier around an op-amp followed by a
> >> one-pole LPF (a cap going to ground). There are numerous examples of
> >> various effects containing this sub-circuit on the web.
> >>
> >> You might find this article interesting:
> >>
> >> http://www.geofex.com/Article_Folders/noteproc/noteproc.htm
> <http://www.geofex.com/Article_Folders/noteproc/noteproc.htm>
> >> <http://www.geofex.com/Article_Folders/noteproc/noteproc.htm
> <http://www.geofex.com/Article_Folders/noteproc/noteproc.htm>>
> >>
> >>
> >
> >
> >
> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> <http://www.cgs.synth.net/>
> >
> >Yahoo! Groups Links
> >
> >
> >
> >
> __________________________________________________________
> Ken Stone sasami@... <mailto:sasami%40hotkey.net.au>
> Modular Synth PCBs for sale <http://www.cgs.synth.net/
> <http://www.cgs.synth.net/>>
> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/
> <http://www.blaze.net.au/%7Esasami/>>
>
>