Mixing two signals with a single knob using PatchMaster and XFADE


I am new to the modular world and this community, so I apologize if this is a silly question.

I am looking for a way to mix two audio signals using a single knob with PatchMaster (I have a limited number of midi knobs and thought two, one for each channel, was excessive).

The behavior I am after:

When PatchMaster knob is at 0 signal A is at 100 and signal B is at 0 When PatchMaster knob is at 50 signal A is at 100 and signal B is at 100 When PatchMaster knob is at 100 signal A is at 0 and signal B is at 100 With smooth CV in between

My original thought was to just map the PatchMaster knob to both channels but invert one so the signals were evenly mixed when the control knob was halfway. But this made it so the evenly mixed signal was quieter than either extreme. I thought about also mapping the mix level to compensate, but quickly realized I would need some kind of bell-curve shape to make that work and got stuck.

I finally came up with a solution that produced the behavior that I wanted using comparators and signal multiplication, but it seems incredibly bulky. I have to imagine there is a better way to do this.

rareairbikeco_single_knob_two_sided_mixer_issue.vcv (2.1 KB)

So, if anyone can think of a better solution, or point me in the direction of something that could help me achieve this with less modules, let me know!

Thank you very much!

Hi @rareairbikeco , and welcome to the forum!

I think your solution is ingenious :slight_smile:

If I understand correctly, you basically want a crossfader that does a unity mix (A+B) in the center and cuts to either full A or full B on either side. I’m not in front of Rack right now but if I recall correctly you might try Bogaudio XFADE with Shape in the fully clockwise position (^) and the LIN button (probably) off for audio–is that what you’re after?


Good call for the Bogaudio CrossFade. NOPE-> I believe what he asked for calls for the shape in the center, and linear mode on. Whether that gives the desired result is another question.

Oops - You were correct regarding the shape, definitely fully clockwise. And you are probably right that the OP will be most satisfied with LIN off. But I think he described linear behavior.

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There is this solution :

I use shapemaster with the CV “playhead” fonction, so I can “read” the position with the knob. I had to add a scale and offset because shapmaster’s shapes have to start and end at the same amplitude, so therefore extreme position brought a jump in amplitude (offset is 0.01, scale 0.98). I use shapemaster’s VCAs and mix the signal, there you go. Here is the module selection in case you want check it. crossfade with both signals at noon.vcvs (31.8 KB)


Actually they don’t Tana. In the channel settings you can set ‘First/Last Nodes > Decoupled’ - this is really useful in CV Playhead mode to avoid the jumps that you refer to (that’s precisely why we added the feature :slight_smile: ). It’s also really handy when using the PingPong play mode.


Ouuuuuh, thank you for that !!! Yeah, obviously there was a way, damn menus and damn bad habit of not looking what’s there. Anyway, once again shapemaster saves the day !


Ah yes, the Bogaudio xfade does exactly what I need. So simple. I knew that there had to be a module out there that did this!

I also thought about using shapemaster, but it seemed like overkill for this. I want to explore this module soon though, seems like there is a ton of functionality for more complex shapes/behaviors.

Thank you to all responders/helpers! I will likely be back at some point with another Q.


Awesome! Glad to hear it! BTW one useful forum convention is to mark the thread “solved”–as the thread creator you can pick a post (probably your post above) to route others towards the answer. Sometimes people edit the title to reflect the solution or fully articulate the problem.

ShapeMaster is among the very best that the Rack library has to offer, and that’s saying something! It’s truly wonderful.

Absolutely any time! :slight_smile:

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Ok got it, thank for the forum etiquette tips!

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