Yahoo Groups archive

Cgs synth

Index last updated: 2026-04-28 23:16 UTC

Thread

Voltage Controlled Slope - Processor Section

Voltage Controlled Slope - Processor Section

2010-09-11 by spiralsect

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.

Re: Voltage Controlled Slope - Processor Section

2010-09-11 by sasami@hotkey.net.au

Not tried either but suggestions are : decrease the value of the input
resistor, or increase the value of the second feedback resistor only.

Ken
Show quoted textHide quoted text
>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/>

Re: Voltage Controlled Slope - Processor Section

2010-09-12 by spiralsect

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.
Show quoted textHide quoted text
--- 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/>
>

Re: Voltage Controlled Slope - Processor Section

2010-09-12 by spiralsect

Increasing the feedback resistor in the second op-amp works a treat; thanks Ken.

Cheers,
Adam.
Show quoted textHide quoted text
--- 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/>
> >
>

Re: Voltage Controlled Slope - Processor Section

2010-09-12 by Mr Waverly

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
Show quoted textHide quoted text
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]

Re: Voltage Controlled Slope - Processor Section

2010-09-12 by spiralsect

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.
Show quoted textHide quoted text
--- 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]
>

Move to quarantaine

This moves the raw source file on disk only. The archive index is not changed automatically, so you still need to run a manual refresh afterward.