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CGS04 Mixer issue

CGS04 Mixer issue

2017-08-12 by freq63

I added a pot as master level control but it acts weird no matter how.

Warning it’s getting pretty loud, but it shows what happens when the pot is getting fully opened:
http://www.batchas.com/serge/CGS04-Mixer-issue-pot-out.mp3

I replaced the 100k* resistor with the pot (no matter which value it acts the same. I checked with different pots, changed TL072 etc. Same issue):
http://www.batchas.com/serge/Serge-CGS04-Issue-pot-out.png

I also installed 47pF between pin 1 & 2 of TL072 as recommended on Ken's page (https://www.cgs.synth.net/modules/cgs04_mix.html).

The circuit is so simple I'm really wondering what I am doing wrong.


Thanks in advance for any help!

Re: CGS04 Mixer issue

2017-08-12 by Synth asaurus

Hi,
I think it would be better to remove the pot and replace the 100K resistor.

Connect the clockwise pin of the pot to the output (to the right of the 1K output resistor), connect the counter-clockwise pin of the pot to ground, and the center pin of the pot will be your new output.

Andrew

Virus-free. www.avg.com
Show quoted textHide quoted text
On Sat, Aug 12, 2017 at 9:39 AM, freq63@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

I added a pot as master level control but it acts weird no matter how.

Warning it’s getting pretty loud, but it shows what happens when the pot is getting fully opened:
http://www.batchas.com/serge/C GS04-Mixer-issue-pot-out.mp3

I replaced the 100k* resistor with the pot (no matter which value it acts the same. I checked with different pots, changed TL072 etc. Same issue):
http://www.batchas.com/serge/S erge-CGS04-Issue-pot-out.png

I also installed 47pF between pin 1 & 2 of TL072 as recommended on Ken's page (https://www.cgs.synth.net/ modules/cgs04_mix.html).

The circuit is so simple I'm really wondering what I am doing wrong.


Thanks in advance for any help!


Re: CGS04 Mixer issue

2017-08-13 by Ken Stone

no idea! Instead, have 1 go to the CW end of the pot, CCW end to 0V and wiper to the resistor that was previously connected to pin 1. 100k fixed resistor in the feedback. This of course assumes you are using it as a mixer and not a processor. The master volume won't work with it in processor configuration (red circuitry).
Show quoted textHide quoted text
On Sun, Aug 13, 2017 at 3:19 AM, Synth asaurus synthasaurus@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Hi,
I think it would be better to remove the pot and replace the 100K resistor.

Connect the clockwise pin of the pot to the output (to the right of the 1K output resistor), connect the counter-clockwise pin of the pot to ground, and the center pin of the pot will be your new output.

Andrew

Virus-free. www.avg.com

On Sat, Aug 12, 2017 at 9:39 AM, freq63@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

I added a pot as master level control but it acts weird no matter how.

Warning it’s getting pretty loud, but it shows what happens when the pot is getting fully opened:
http://www.batchas.com/serge/C GS04-Mixer-issue-pot-out.mp3

I replaced the 100k* resistor with the pot (no matter which value it acts the same. I checked with different pots, changed TL072 etc. Same issue):
http://www.batchas.com/serge/S erge-CGS04-Issue-pot-out.png

I also installed 47pF between pin 1 & 2 of TL072 as recommended on Ken's page (https://www.cgs.synth.net/mod ules/cgs04_mix.html).

The circuit is so simple I'm really wondering what I am doing wrong.


Thanks in advance for any help!





--
Ken Stone otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>

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