3x3 Matrix Mixer Project

Would anyone be interested in this project?
For some reason I’m really into mixers lately.

3x3 layout … it will be a large project if I decide to do this. 5x LM6172
and I have 1 stage left, maybe an inverted input but that would mean 3 more pots. and there are already 12 :upside_down_face:


  • feedback routing
  • color mixing.

features: (for now)

  • 3x input with 3x pots per channel - so 9 pots
  • 3x output with 1x gain pot per channel

Things that might change:

  • gain pots: they can be in the feedback loop ? for better amplification / soft keying?
  • inverted inputs without pots. IDK if that is useful, but it would save panel space
  • SMD? maybe?

I’m open for idea’s!


well I was just thinking about buying a doepfer matrix mixer - as there were no diy ones I could find that I liked

so why not

conditional add to group buy - if you do this I need 5 more


Yep definitely interested in this!

Schematic looks OK – but make sure you ground the noninverting input on the unused opamp, and connect a 1K resistor from inverting node to output. That way you won’t get any potential ringing or oscillation from the floating terminals.


I might want to use that last opamp for something more useful, that is why it is still floating :slight_smile:
Maybe I’ll add a inverted input, or at least a mod input for expansion possibilities. to keep the DIY blood flowing!

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I can definitely see me wanting at least one of these please yes

Also Interested! Nice work @reverselandfill


These modules are not the most exiting things you could think up (as opposed to filters, effects and oscillators) but it is where I am right now in my personal electronics development. I’m mostly building on opensource schematics by LZX and others, adding some features I think might be useful. The help from @creatorlars is invaluable!

And I do think it is cool to have more DIY video projects in the ever expanding universe of modular !


Hey, what’s up? I have been working on something like this too. I was doing a 4x3 matrix. I just got access to a desktop milling machine, so I was going to prototype it.

I have another surface mount variation using a max4392. I’m willing to distribute whatever and collab if anyone is interested!


As mentioned in the previous 2x2 mixer thread, I am now finding that yes…buffers are our friends. Rev 2 Doh!

this sounds useful and great!

if I can get one built then I’d be in!

I’m back from Italy, so this project will continue this month.
I’ll keep you updated!



There are 12 pots right now and there might be more, so I’m wondering how I will do the panel spacing.
Personally I’m not fond of trimmer pots and small knobs, but this can keep the panel small.
This will be a performance module, so I’d prefer space over size

so what to do?

1: use 9mm vertical pots - larger panel with enough space to wiggle
2: use 9mm trimmer pots - smaller panel with little room
3: 9mm pots with small knobs - inbetween solution. medium panel size

I think I’d prefer option 1, but any is fine

I just built an audio matrix mixer from york modular - which is 4 channel 20 pots and 14 hp - the designer recommends alphas - mainly as they are bolted to the panel and therefore offer a bit more support to the pcb - but I used short trimmers instead and it’s ok - the same trimmers will take the small knobs (from thonk for example) - but that has 8 jacks total and not 6 for support

yes, I also prefer the bolted ones. else I will need to add screws to the panel. or place the jacks on to and bottom for stability

I saw those small knobs at thonk , this was the reason for this question :slight_smile:

it’s only really the kits that are the issue (other than size - and that’s easily solved - the inevitable bigger/new case)

the pcb and panel holes are the same size - so builder’s discretion for supplying parts if they don’t buy a kit

same red panel colour as the function generators?

Yes, I was thinking of a red panel with geometrical shapes such as the TFG.

trimmers are cheaper. but I don’t like them much.
I think I’ll stay with the 9mm alpha pots bolted to the panel., as design
I might consider those small knobs and thighter positions

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I’d prefer option 1 but 3 is okay as well. I regularly use NLC’s Cluster Mixer so I can deal with a little bit of cramped space. :slight_smile:

I’ve been using these for my mixer. It has 12 pots, and fits on a 4" x 4.6" board. They’re pc mount, so the panel can mount directly to them & the board. Seems like there’s enough space to get your fingers in there. That’s also with using BNC connectors, so it could be even smaller.