The complete guide to matrix mixers
A matrix mixer is one of the most powerful tools you can add to a synth or recording setup, but arguably one of the least well understood. So in this blog post, we’ll take a deep dive into the topic - looking at where matrix mixers came from, what’s currently on the market, and some of the ways you can use them, from feedback patching to effects routing and a whole lot more.
Plus, who better to talk about matrix mixers than the designers behind some of the best ones around? We caught up with Finlay and Jamie from Future Sound Systems, Gianluca from Herbs & Stones and Aimo from Manifold Research Centre to hear more about their designs and learn their favourite tips and tricks. Ready? Let’s enter the matrix...
What is a matrix mixer?
In a nutshell, matrix mixers let you take a bunch of inputs, then route and mix them in various combinations to a bunch of outputs. You could use a matrix mixer module to route audio or control voltage (CV) signals within a synth, for example, or you could use a standalone unit to create routings and feedback loops with effects units or guitar pedals.
One of the earliest examples of the concept is the distinctive pin matrix in the EMS VCS3 synthesiser (pictured below) launched in 1969. This lets you connect audio and modulation sources (like oscillator and envelope outputs) to audio and modulation destinations (like filter and FM inputs) within the synth by inserting pins into a grid, without needing patch cables. The ‘mod matrix’ is a concept you’ll find in hundreds of synths to this day - although it’s more commonly implemented via software rather than a physical pinboard.
The epic ARP 2500 from the same era used switch matrices at the top and bottom of its cabinets to make connections between modules. These took the form of 20-way slide switches and were designed to eliminate the unruly tangle of patch cables that characterised most other modular synths of the time.
Since those early days, matrix mixers have evolved considerably. Some use banana connectors or TRS jacks to make connections, while others use magnets; some let you control the levels of the signals you’re mixing, either with manual attenuators or VCAs; some use digitally controlled switches to let you save and recall states… but the underlying concept of routing and combining signals has stayed pretty much the same.
What can you do with a matrix mixer?
Signal routing: at its simplest, a matrix mixer offers a quick and convenient way to patch common modulation sources to destinations in a modular synth. For example, patch your oscillator, envelope and LFO outputs to the matrix mixer inputs, and patch the outputs to the various audio and control inputs on your VCAs and filters. Then it’s easy to assign the same envelope to control a VCA, say, while also routing it to the filter cutoff.
Parallel processing: matrix mixers make it super-simple to duplicate a source and run it through one or more processing chains in parallel with the dry signal. This is particularly handy if you use a lot of pedals - whether you’re looking to achieve ‘New York’-style parallel compression or experiment with combinations of more extreme distortion.
Effects sends: using a matrix mixer with attenuators or VCAs, you can patch multiple audio sources to the inputs of the matrix mixer, and patch the outputs to your effects modules or pedals. Then you can create a unique mix of inputs for each one. Want to bathe the lead synth in cavernous reverb but keep the drums dry? Just turn down the drums in the mix being sent to the reverb. You can route an effect’s output back to a matrix input, either to send to other effects to form a chain, or to feed back on itself - which leads us nicely on to…
Feedback patching: this is where matrix mixers shine. Routing outputs back to inputs and carefully adjusting levels can open up a new world of sonic possibilities. Feed the output of a delay back into itself and try routing it through a filter en route. Feed a smidge of the bandpass output of a filter back into its audio or FM input and listen to the lowpass output. The sky really is the limit for adventurous sound designers!
Complex modulation: want to make a couple of simple LFOs sound much more complex? Want to add a bit of wobble to a simple envelope? You need a matrix mixer, mate! Throw your modulation sources at the inputs and adjust the weighting of each one in the output mixes to get a set of related but different outputs. For bonus points and even more interesting shapes, try using feedback (again!)
Designer insights: Future Sound Systems
Finlay Shakespeare and Jamie Neale are the brains behind Bristol-based Future Sound Systems. Their line-up includes a Eurorack module (the MTX9) and a standalone unit (the MTX8), both of which use a pin matrix interface inspired by the legendary VCS3.
Jamie says: “The VCS3 is obviously an icon, and I think the one we had access to at university definitely piqued our interest in pin matrices (in contrast to the Eurorack spaghetti Finlay was accustomed to). Thinking about the VCS3, the main thing that comes to mind is how weird it is. The pin matrix seems like the least strange thing about it to me, which maybe says something about how useful and invisible pin matrices can become once you get used to them.”
“Pin matrices are great because they make patching clearer and let you do things you simply can’t with patch cables.”
The genesis of Future Sound Systems’ MTX design also dates back to the pair’s uni experiences, as Jamie explains: “We made the MTX range for two main reasons: firstly, pin matrices are fantastic for workflow, and secondly, back in our university days, Finlay came up with an incredibly simple (and novel) way of creating a pin matrix. This allowed us to make a pin matrix very affordable compared to previous designs. We couldn’t resist building it so we brought out the MTX9 and MTX9a Eurorack modules.
“Pin matrices are great because they make patching clearer and let you do things you simply can’t with patch cables. This can be applied to any person dealing with signal routing, not just modular synths. As a result, in 2020, we brought out the MTX8 and MTX8 Guitar, to try and bring the pin matrix workflow to anyone working with audio, be it an artist or producer with outboard, or a guitarist with a pedal collection.
“Prior pin matrix designs have been expensive and fiddly. We have always been perplexed by the cost of Ghielmetti matrix modules (the type found in the VCS3), which as a component alone, cost more than the MTX9. Ghielmetti matrices also have the major downside of requiring a proprietary, high-precision pin with an internal summing resistor. Our design uses the ubiquitous 2mm banana pin, and the summing resistors are provided in the matrix itself. Our design is also very easy to disassemble and repair should anything wear out.”
There are some specific advantages to using pins rather than jacks to make connections, as Jamie explains: “With sources and destinations clearly labelled, you don’t have to pick through a nest of cables to see what’s going on. Pin matrices also allow you to split or sum signals without resorting to stacking jacks. This is huge, as it allows for instant parallel processing or for feedback paths to be created.”
Finlay adds: “The physical act of dropping a pin into a matrix point is easier than plugging a cable in, especially when the cable has to be found in a pile of disparate bits and pieces: check the cable works; oh no the ground's gone; oh shit it's too short; back to the pile of cables, find another one; oh no the cat's chewed this one up; oh I've got a cable with one end correct but the other end is the wrong connector; oh I think I've got an adaptor for that; oh no the adaptor's broken…”
Future Sound Systems MTX9A Eurorack Active Pin Matrix Module (inc MTX9A)
£165.00
The MTX9 presents a new take on an old classic - the pin matrix, famously incorporated into EMS and Maplin synthesizer designs. The MTX9 provides...… read more
Jamie’s a big fan of the possibilities for feedback and parallel processing which a matrix mixer offers. He explains: “I think my favourite thing to do with the MTX range is parallel processing and feedback. The MTX8 in particular, because it’s not a Eurorack module, means that it introduces non-synth people to these concepts. Often people have never heard of parallel processing, and the idea of plugging an output back into an input is mind-blowing. On the MTX8 Guitar, this is of course encouraged. Pedals and outboard do wild things when fed back.
“I really feel like the MTX8 Guitar is a must for anyone with more than two pedals (producers and artists included) as you can just plug your pedals into it and re-configure at will. No need to buy loads of patch cables and faff around with Velcro. Plus, all the parallel processing it enables you to experiment with. The thing that makes the MTX range stand out is simply that they are the only affordable pin matrices that come ready to use.”
Future Sound Systems MTX8 (Guitar) Pin Matrix Signal Router
£449.00
Now you can take advantage of the creative control and possibilities of the FSS MTX range, without the need for a Eurorack system. MTX8 lets...… read more
Designer insights: Herbs & Stones
Gianluca Herbertson runs Herbs & Stones in Italy and describes his 4x4 standalone unit, Pathways, as “a routing machine that lives at the crossroads between signal mixing and synthesis”.
He says: “My first approach with sound synthesis was through the misuse of guitar FX pedals, a thing I learned by attending noise shows in my late teens. During those years I built some passive matrix mixers and really enjoyed the vast sonic possibilities that sprouted from a simple machine like that.
“Fast forward some years, and while I was designing the Solid Felt stereo filter that idea came back to mind. So I took some days off and started experimenting with it again, but this time with VCAs, and I was really happy with the possibilities CV control gave over feedback and routing. Adding CV generators and extractors was the natural next step.”
Pathways certainly brings some unique twists to the classic matrix mixer paradigm by incorporating CV control over each of the 16 intersections, gain/drive controls for the inputs, an envelope follower, a clock divider and LFOs. Using self-patching, it can even turn into an oscillating drone synth - a real powerhouse!
“The thing that I enjoy the most is using FX units in a way that wasn't intended for them.”
Gianluca adds: “Since all matrix mixers work by the same principle, I think the thing that makes Pathways stand out is the built-in control signal generators and the fact that it can work as a bridge between desktop instruments/effects and the modular world.
“The thing that I enjoy the most is using FX units in a way that wasn't intended for them: synthesising a drum beat with just a bass overdrive pedal; generating droning soundscapes with delay-based effects; and so on. It’s almost impossible to get the same result twice and there's something endlessly fascinating about it, oscillating back and forth between planning and surprise.”
Herbs & Stones Pathways Desktop Matrix Mixer
£489.00
Pathways is a modular matrix mixer designed for feedback manipulation, creative routing, weird synthesis… and many other things. Features • 4x 1/4″ inputs with gain...… read more
Designer insights: Manifold Research Centre
Aimo Scampa is another Italian designer, and he’s the brains behind not one but two unique evolutions of the matrix mixer. While working for our fellow Glaswegians Instruo a few years ago, he came up with the Lion - a pin matrix-based module that was the starting point for his journey into product development.
Aimo explains: “I had been working for a year or so at Instruo, and all I knew how to do was solder modules and play with them. The environment was very creative and while I was soldering I would hear my colleagues bouncing around ideas for modules and speculating what circuitry would be needed to develop those ideas. It was a great mental exercise and slowly I started getting involved in those discussions.
“I also got to the point where I was playing a lot with my modular and was looking for a routing system that would let me change my signal chain quickly without having to repatch constantly. At the time I was doing a sound engineering degree in Cumbernauld (which by the way is a Brutalist jewel - I would recommend everyone to visit!) and we had these beautiful patchbays in the studio and I loved the system. I realised it was the same concept behind the matrices on the VCS3 or the Synthi.
“I started to look around for the manufacturer as I wanted to get my hands on them to work on a custom version. But then when I expressed my idea to my work colleagues one of them said, ‘Why don’t you just design one?’ He helped me find a solution for the signal transmission through the pins, and then Jason [Lim - Instruo’s founder] introduced me to PCB design.
“At the end, when my module was ready and I built the first prototype, Jason asked if I was interested in putting the Lion on the Instruo line. That was the spark that started me designing instruments, and I’ll always be grateful for that moment.”
Instruo Lion Eurorack Pin Matrix Mixer Module
£289.00
The Instruo lìon is a 6x6 matrix mixer with a pin style interface similar to those found on iconic modular synthesizers of the 1970s. Its...… read more
He adds: “I like the way we used stereo jacks as pins. I remember when we released it, we discovered that Rob Hordjik did the same on his matrix! It’s crazy how we came to the same conclusion. I like how Lion focuses mainly on routing rather than mixing, as for me that’s the most important aspect of a matrix (although it does have a normalisation system that allows you to mix signals at different levels). I also like the fact that it's knobless and that you can use it as a mult too! It's a blank slate, a modular module.”
Aimo went on to found Manifold Research Centre as an outlet for more of his own designs and made waves earlier this year with the beautiful The Map Is Not The Territoire (TMINTT) - a standalone matrix that uses magnets to make connections and looks more like an esoteric board game or puzzle than an electronic instrument.
Manifold Research Centre The Map Is Not The Territoire Magnetic Desktop Matrix Mixer
£439.00
TMINTT is an active routing and summing matrix that works with voltages up to the Eurorack modular format. Its principle is quite simple: inspired by...… read more
He says: “TMINTT was inspired by Meng Qi's Magnet Matrix, which was a one-off, extremely limited run of a passive matrix mixer that used this incredible idea of magnets as a patching system. That was some time after the Lion - I was still quite obsessed with matrices at the time - and since it was impossible to get my hands on one, I made my own.
“I made a prototype - you can see it on my website; it's called Lake Lee - and then I got in touch with Meng Qi and asked for permission. He gave me the OK and shared his dream of seeing a patching system like this on an instrument that would generate signals. That's when I started to work on the Tetragrid, and TMINTT was put to one side for some years before I decided to revive the project.”
With his love of “weird interfaces” and disdain for stereotypical music-making processes, it’s no surprise that Aimo is an avid and adventurous user of matrix mixers. He says: “I love to use matrix mixers for cross modulation between multiple VCOs (or multiple envelopes to create patterns that I use then to modulate my VCOs). Or I’ll use the matrix only for FX and create complex chains.
“The main thing is: feedback loops! The beauty of matrix mixers is that they allow you to reroute signals quickly, create different parallel signal chains (i.e. think about parallel compression, comb filtering, ….) or introduce feedback loops between feedback loops between feedback loops in parallel with feedback loops. Did I mention feedback loops? No, but seriously, you can easily introduce them at any point.”
He adds: “When I have no ideas, I pick a bunch of modules, plug them into TMINTT and start patching randomly and see where it goes. It can be a useful tool but it can be daunting too. I wouldn’t use it to create a full classic synth patch, for example, but I would try to use it on only a part of the patch - audio or CV routing, cross modulation, FX chains, you name it…”
“The beauty of matrix mixers is that they allow you to reroute signals quickly, create different parallel signal chains or introduce feedback loops between feedback loops between feedback loops in parallel with feedback loops. Did I mention feedback loops?”
Other matrix mixer options
Aside from the models discussed above, we also stock a few other matrix mixers worth considering:
ADDAC 814 6x6 Eurorack Stereo Matrix Mixer System (A+B)
£342.00
We say... ADDAC's eagerly awaited matrix mixer is a bit of a monster - 6x6, full stereo, with the option to expand to 12x6, 6x12,...… read more
Doepfer A-138M Eurorack Matrix Mixer Module
£138.00
The A-138m is a 4x4 mix matrix where you can mix up to four incoming signals in all possible variations to four outgoing switches. The...… read more
4ms VCA Matrix Eurorack Modue
£349.00
The VCA Matrix from 4ms is a playable 4x4 matrix of 16 VCAs. Four CV or audio inputs can be routed in any amount/combination to...… read more
Erica Synths Desktop Matrix Mixer
£477.00
As Eurorack users may know, it can be challenging to change a patch radically during a performance, therefore diverse performances require large systems or they...… read more
AtoV Project MMx2 Eurorack Mixer Utility Module (Black)
£169.00
Expand the power of your modulations with the MMx2, a dual-pack module designed to bring flexibility and creativity into your system. Each MMx2 package contains...… read more
Photo credits
- Matrix background by Markus Spiske on Unsplash
- VCS3 photo by Rosa Menkman - originally posted to Flickr as EMS VCS3, CC BY 2.0
