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Building the CGS Synthacon

Building the CGS Synthacon

2006-05-19 by Rune Sagevik

Hello everybody.
I just received my Synthacon PCB from Ken, and a couple of questions
suddenly came up..
I must admit that I`m a total newbie to DIY synth, with no eelctronics
skills whatsoever.. (I`ve built one simple module so far.. thats all)

I`ve seen several solutions around the web regarding this filter, and
decided to try a version with built in "input mixer" and CV control
for both freq. and res. (as seen here http://guitarfool.com/modules/
images/Synthacon01.jpg)
but.. when reading Ken`s web pages and looking at this http://www.cgs
synth.net/modules/pic/wire_cgs35_syntha_vcf_r1.gif
as far as I can see here there are only one CV input pluss two knobs,
one for freq. and one for res.
So what I was wondering was.. where would I add pots. to control/mix
the input signals, and what type of pots would I need to use?
and the same with the CV. Where and how would I add an "amount knob"
to control the amount of the CVin being used to control the freq.
And also.. how to do the same to the Resonance? add a Cv jack and an
amount knob.

Hope someof you can help me with this.. or point me in the right
direction at least :)

thanks in advance.
Rune

Re: Building the CGS Synthacon

2006-05-19 by Ryan Williams

I expect you are talking about the 'All Input'? that input is actually just
connecting a single input to the lowpass, highpass, and bandpass inputs. the
filter itself acts as a sort of mixer for those signal. just connect that
jack to each of the other jacks, normally closed contacts.

the resonance can not be CV controlled without a fairly major modification
to the circuit. I don't recall seeing any good design for this yet.

to add a frequency cv amount pot, it would connect just like the frequency
pot except the +15 is replaced with the CV input jack. on the wiring diagram
you linked, connect the pot like this: connect pin 1 of the pot to ground,
pin 2 of the pot to the point on the PCB where the frequency jack current
connects, connect pin3 of the pot the jack connection that is currently used
(TP).

that will give you a resistve voltage divider. you can use a 100k or
somewhat smaller pot if you like (not really critical).
Show quoted textHide quoted text
On 5/8/06, Rune Sagevik <rsagevik@...> wrote:

> I`ve seen several solutions around the web regarding this filter, and
> decided to try a version with built in "input mixer" and CV control
> for both freq. and res. (as seen here http://guitarfool.com/modules/
> images/Synthacon01.jpg)
> but.. when reading Ken`s web pages and looking at this http://www.cgs
> synth.net/modules/pic/wire_cgs35_syntha_vcf_r1.gif
> as far as I can see here there are only one CV input pluss two knobs,
> one for freq. and one for res.
> So what I was wondering was.. where would I add pots. to control/mix
> the input signals, and what type of pots would I need to use?
> and the same with the CV. Where and how would I add an "amount knob"
> to control the amount of the CVin being used to control the freq.
> And also.. how to do the same to the Resonance? add a Cv jack and an
> amount knob.
>
> thanks in advance.
> Rune
>


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

Re: Building the CGS Synthacon

2006-05-19 by Richard Brewster

Here is a schematic for the CV inputs that some of us have used:

http://www.pugix.com/bottom-cabinet-lower.htm#synthacon
http://www.pugix.com/images/steinervcf-mod-mine.gif

Richard Brewster

Ryan Williams wrote:
Show quoted textHide quoted text
>I expect you are talking about the 'All Input'? that input is actually just
>connecting a single input to the lowpass, highpass, and bandpass inputs. the
>filter itself acts as a sort of mixer for those signal. just connect that
>jack to each of the other jacks, normally closed contacts.
>
>the resonance can not be CV controlled without a fairly major modification
>to the circuit. I don't recall seeing any good design for this yet.
>
>to add a frequency cv amount pot, it would connect just like the frequency
>pot except the +15 is replaced with the CV input jack. on the wiring diagram
>you linked, connect the pot like this: connect pin 1 of the pot to ground,
>pin 2 of the pot to the point on the PCB where the frequency jack current
>connects, connect pin3 of the pot the jack connection that is currently used
>(TP).
>
>that will give you a resistve voltage divider. you can use a 100k or
>somewhat smaller pot if you like (not really critical).
>
>On 5/8/06, Rune Sagevik <rsagevik@...> wrote:
>
>
>
>>I`ve seen several solutions around the web regarding this filter, and
>>decided to try a version with built in "input mixer" and CV control
>>for both freq. and res. (as seen here http://guitarfool.com/modules/
>>images/Synthacon01.jpg)
>>but.. when reading Ken`s web pages and looking at this http://www.cgs
>>synth.net/modules/pic/wire_cgs35_syntha_vcf_r1.gif
>>as far as I can see here there are only one CV input pluss two knobs,
>>one for freq. and one for res.
>>So what I was wondering was.. where would I add pots. to control/mix
>>the input signals, and what type of pots would I need to use?
>>and the same with the CV. Where and how would I add an "amount knob"
>>to control the amount of the CVin being used to control the freq.
>>And also.. how to do the same to the Resonance? add a Cv jack and an
>>amount knob.
>>
>>thanks in advance.
>>Rune
>>
>>
>>

Re: Building the CGS Synthacon

2006-05-20 by Rune Sagevik

> I expect you are talking about the 'All Input'? that input is
actually just
> connecting a single input to the lowpass, highpass, and bandpass
inputs.

No I was thinking of an actual mixer part where you have a level knob
for each input. I guess it is just to put in the right pot between the
jack and the input on the pcb? But the all input jack would be nice as
well.
Thanks for the tip.

Rune

Re: Building the CGS Synthacon

2006-05-20 by Rune Sagevik

Thanks a lot. I`ll definately check this out.
I`m not particularly trained in electronics, so I have to do a couple
of trial and error projects to get comfortable with the whole DIY
stuff.
I thought I`d try to make the most basic version work first, and then
I`ll try and modify it with additional knobs/jack etc. later on.
So there will probably be more questions..

Rune
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, Richard Brewster <pugix@...> wrote:
>
> Here is a schematic for the CV inputs that some of us have used:
>
> http://www.pugix.com/bottom-cabinet-lower.htm#synthacon
> http://www.pugix.com/images/steinervcf-mod-mine.gif
>
> Richard Brewster
>

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