[sdiy] Passiv mixer question

[Ray Wilson]

Tom, you are grounding the output when you set either pot to "off" (fully 
counter-clockwise). You need resistors from the pot wipers so that the pots 
don't influence one another as much. To get rid of the inter-pot influence 
altogether you need to use a summing op amp.

Here is an illustration of what I mean:
http://www.musicfromouterspace.com/analogsynth/oddsandends.html#SIMPLEAUDIOMIXER

Cheers

Ray


----- Original Message ----- 
From: <tom.adam at telenet.be>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Friday, July 28, 2006 6:48 AM
Subject: [sdiy] Passiv mixer question


>
> Guys,
>
> I made a stereo mixer / mono attenuator to use as an output module to go
> straight to my mixer.
> The stereo mixer works real great, but the mono (passive) mixer is acting
> kind of strange.
> I just wired up 2 100k pots like this: pin1: hot input signal, pin 2 :
> output signal, pin 3: ground.
> I connected the output signals together.
> The strange thing that's happening now is the following:
> When using only one input, both pots influence the output level. So when i
> turn one pot fully CCW, I hear nothing, independent of which pot I turn.
> So, will adding a resistor on pin 2 of each pot solve this problem? Is 
> 100K
> a good value for this resitor?
>
> Cheers,
> Tom Adam
>
>
>