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Author Bananalogue Serge 3p mixer
chamomileshark
 anyone care to enlighten me on what this does? Yes I've had it for years and I twiddle the knobs but I'm not sure what it is doing exactly, especially when I have 3 audio inputs, everything at 12 o'clock and I move one of the knobs off the 12 o'clock position. ..and what does it do to CVs? yeah I know, I should know
dude
 is it not a polarizing mixer? i believe it can take signals and attenuate them either in the positive or negative range. attenuversion. you could, say take a 0-5v lfo and invert it or even attenuate and invert it. or invert a gate.
Hi5
 It is an attenuverting 3-1 mixer
chamomileshark
 ok, so 12 o'clock is basically unity for audio - but while 2 o'clock is louder..so is 10 o'clock? or are you saying that 10 o'clock is louder but inverting the waveform?
Hi5
 12 o'clock should be no gain = 0 as you move to the right you get positive gain/attenuation( I am not sure if this circuit actually has gain or not) move to the left and it is the same but the phase of your signal is inverted. with audio there will not be a difference in sound between positive and negative attenuation but with cv you will have a drastic difference. think of it this way, this device is multiplying the inputs by their pot values. as you move right you are increasing your multiplication value up to +1. towards the left up to -1. with a fixed dc voltage of say +5v at the input at 3o'clock your output will be around +2.5 at 6o'clock it is -2.5. all the way to the right +5 all the way left, -5. These values may be off a little if the design has gain beyond 1 but you get the picture.
Cat-A-Tonic
 chamomileshark wrote: ok, so 12 o'clock is basically unity for audio - but while 2 o'clock is louder..so is 10 o'clock? or are you saying that 10 o'clock is louder but inverting the waveform?

12 o'clock (center detent of the pot) should be zero (nothing passed).
Turn clockwise for 'more'.
Turn counter-clockwise for 'inverted more'.

The Blacet Mixer Processor does the same + output voltage offset
& has an additional single channel polarizer/offsetter.
Blacet detents are at 9 o'clock instead of 12.
It can repanelled to fit in 1FU.

BugBrand DC Mixer also works like the Serge 3p,
but it has 2x 2-1 mixers that can be switched to 1x 4-1 mixer.

Polarizing mixers are useful for a number of things:
- Use it like a normal audio mixer but with half the pot travel + inversion of the audio available
(useful for mixing filter types or wave-shapes from a module with multiple outputs).
- Use it to derive voltage patterns from gates/triggers (like a Binary Zone).
- Use it to send envelope feedback (and other voltages) to attack/decay CV inputs for precise control of envelope shape per stage.
DGTom
 3P also adds DC to the output (4th pot) or can be used as a bi-polar voltage source. For all intents & purposes the 3P is identical in function to the top section of the Blacet, except, the 3P sounds nicer to me when driven hard.
Babaluma
 anyone know what the "span" trim pot on the 3p does? i used to have five of the fuckers, but i'm down to just two now. having the fixed voltage source is really really useful. i use them all the time for all sorts of things!
Kwote
 I have 2 and I like em but there's a bit of bleed through. No full blown silence to be found. Blacet stuff is better for that.
chamomileshark
 thanks all!
diophantine
Bumping this ancient thread, as I recently acquired one of these.

Here's the deal with the "span" trimpot, as per my tests just now with my scope, with a single input signal (Blacet VCO saw) and the input attenuvertor at the maximum:
Fully Clockwise: unity gain.
Center: approx. 2x gain.
Fully Counter-clockwise: approx. 2x gain with distortion.
...with intermediate positions being what you might expect.

Note that this is different from the "span" trimpot on the CGS81 processor, upon which the 3P is based (emphasis below mine).
 Ken Stone wrote: If you are building this as a processor, you need to [use 100k for RS and place a link between the two pads of the SPAN trimmer], as the trimmer only controls gain in the first stage, and as such is of little use.

The 3P's "span" trimmer affects the signal the same way, no matter if you've got the input attenuvertors going + or -.

Hopefully that's helpful to someone in the future...

Anyhow, that brings me to my next question: do people prefer using the 3P as an audio mixer, a CV processor, or both? I'm trying to decide how I want to calibrate it. I do have a Blacet Mixer/Processor, so this isn't my only source of CV mixing. And I have an MOTM-1190 Dual VCA, so it isn't my only source of distortion/overdrive, either.
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