Hi Chris,
There are times when you just need to amplify a sigle a little in order to use it more effectively. For example, blacet VCAs don't fully open with doepfer enveope generators, so something that can amplifiy the envelopes a little would be rather useful. With enough gain, line level signals could also be pumped up to modular level.
I breadboarded the circuit and tried 1M which gives a gain of 10 and 500k (2 1m in parallel as didn't have a 470k handy) which gives a gain of roughly 5. You just need to be careful though as a gain of 10 causes anything above plus or minus 1.5v to hit the rails. I'll probably end up going with a 500k pot in searies with the existing 100k resitor to give me a gain of 1 to 6.
Cheers,
Adam.
There are times when you just need to amplify a sigle a little in order to use it more effectively. For example, blacet VCAs don't fully open with doepfer enveope generators, so something that can amplifiy the envelopes a little would be rather useful. With enough gain, line level signals could also be pumped up to modular level.
I breadboarded the circuit and tried 1M which gives a gain of 10 and 500k (2 1m in parallel as didn't have a 470k handy) which gives a gain of roughly 5. You just need to be careful though as a gain of 10 causes anything above plus or minus 1.5v to hit the rails. I'll probably end up going with a 500k pot in searies with the existing 100k resitor to give me a gain of 1 to 6.
Cheers,
Adam.
--- In cgs_synth@yahoogroups.com, Mr Waverly <waveguide@...> wrote:
>
> Adam,
>
> Would you mind saying why you thought you needed more than the
> standard gain? What were the values you settled on?
>
> Haven't built mine yet and may follow your lead.
>
> Regards
> Chris H
>
> Sent from my iPhone
>
> On Sep 12, 2010, at 5:08 AM, "spiralsect" <adam-v@...> wrote:
>
> > Increasing the feedback resistor in the second op-amp works a treat;
> > thanks Ken.
> >
> > Cheers,
> > Adam.
> > --- In cgs_synth@yahoogroups.com, "spiralsect" <adam-v@> wrote:
> > >
> > > Thanks Ken, looks like some experimentation is in order. I'll
> > breadboard the circuit and try your suggestions before I commit any
> > sort of gain control to my panel design.
> > >
> > > Cheers,
> > > Adam.
> > >
> > > --- In cgs_synth@yahoogroups.com, sasami@ wrote:
> > > >
> > > > Not tried either but suggestions are : decrease the value of the
> > input
> > > > resistor, or increase the value of the second feedback resistor
> > only.
> > > >
> > > > Ken
> > > >
> > > > >Hi,
> > > > >
> > > > >I'm looking at building CGS75 Voltage Controlled Slope and was
> > wondering if
> > > > it was possible to increase the gain of the processor stage. My
> > op-amp
> > > > theory is very rusty but I was thinking that, provided the
> > values are kept
> > > > in proportion, I could just increase the value of the two
> > feedback resistors
> > > > to achieve the required gain whilst keeping the intended
> > > > inverting/non-inverting functionality. Can someone please
> > confirm that this
> > > > is the case?
> > > > >
> > > > >Cheers,
> > > > >Adam-V.
> > > > >
> > > > >
> > > > >
> > > > >------------------------------------
> > > > >
> > > > >The CGS Modular Synth home page: http://www.cgs.synth.net/
> > > > >Yahoo! Groups Links
> > > > >
> > > > >
> > > > >
> > > > >
> > > > __________________________________________________________
> > > > Ken Stone sasami@ otherunicorn@
> > > > Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> > > > Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/
> > >
> > > >
> > >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>