There is no denying that 'utility' modules get a bad rap and are seen by many as uncool. But I see them more as ugly ducklings: no matter how many hip and groovy tone-manglers you have in the rack, by all the right manufacturers, you are going to struggle to get much coherence out of them without some basic utility modules — mults, VCAs, attenuators and, most pointedly, mixers.
Mixers have traditionally been separate discrete studio components, partly because as the channel-count increases, so does their physical size. It would make little sense to have a Eurorack-mounted 20-channel (say) mixer if it left no room for your more interesting generative modules. Thus the attractive idea of making smaller sub-mixers which can be slotted into the rack without too much pain. 4MS have taken this approach and created a little family of units which offer a good balance of features to HP width, and which very cleverly can all be internally linked together to maximise functionality. They also work in stereo — or dual mono if you want — which is not so common in the relatively sparse landscape of mixer modules. They are set up specifically to deal with audio, although nothing is stopping you from mixing CVs with them.
The Listen Four a is 10HP, four-channel stereo mixer with primitive LED metering and a separate headphone output (with level). Channels 1 & 2 are mono inputs with a pan-pot, channels 3 & 4 are stereo inputs, normalled for mono if only the Left input is used. For an extra 2HP the Listen Four Quarters replaces the 3.5mm output sockets with good old quarter-inch sockets, so no more searching for those special interface leads!
I think the trick here is getting a balance between essential and esoteric functions. So there are no CV inputs (to control levels or panning), EQ, nor any sort of effects sends. Maybe in a standalone mixer this would be seen as a negative, but I figure with Eurorack, if you want something to pan, there's a module for that. Similarly, you can effect/EQ sounds inline before they get to the mixer.
I found that fitting a single Listen Four in a three-row P9 case simplified life greatly — just a single pair of leads to the PA Mixer rather than eight (3.5mm to quarter-inch). You can still take outputs directly from other modules, but the added advantage is the Listen's headphone output (3.5mm stereo socket and volume pot) — a godsend for last-minute tuning/tweaking on stage. The really clever bit is that 4MS have come up with a really simple way to access the main audio bus, and a simple jumper lead lets you connect multiple adjacent Listen units (and indeed their Wav Recorder unit) together internally. In this fashion two linked Listen Fours will give you an eight-into-two mixer, and the output from the first unit can be a submix used elsewhere.
The jumper leads also allow you to connect a Listen Up module to the mixers, which is an entirely passive break-out 4HP panel; four quarter-inch sockets allow you to connect in and out of the Listen Four's main bus. There are no trims for levels, but like all the Listen modules, the L/R sockets are normalled so that if you don't plug anything into the Right channel, what is in the Left will appear on both, ie. mono. There is also nothing to stop you using the In sockets as Outs, or indeed accessing two separate Listens, as long as they are physically adjacent. Amazing flexibility for such a simple idea. The Listen Up is available as a DIY kit, though it is so basic I'm not sure of the advantage.
The last unit of the set is the Listen IO. Essentially a 6HP two-part module, each with a two-channel level processor with a single trim control and four LED level ladders. However, this is where it starts to get a bit woolly: 4MS posit the concept of Line-level signals being different from what they call Modular-level signals. Certainly I have always noted that most Module outputs tend to be nicely hot, but had never considered them as a different species!
With the Listen IO 4MS suggest that the top part of the unit takes a Line in signal and allows you to boost this up to Modular level via a Gain pot marked from -Infinity to x30. Similarly, the bottom half is a trim to get down form Modular to Line level, trimming from -Infinity to 0db (Unity). The outputs here have headphone markings (mono plugs will give you the L&R output, stereo plugs get you two times stereo). There are jumper access points too on the back. Eventually I stopped worrying that I couldn't find any hard data for what defined Modular level, and just got on with using the Listen IO as a really useful level adjusting tool, which it indeed is!
So that's it really. A suite of really neat mixer (and related) modules, cleverly thought out and very flexible. There are just a few extra features to note: the Listen Four has a switch next to the outputs which offers the choice of Line or Modular level, the upshot of which is it is much louder in Modular mode! On the Listen Four Quarters this switch offers a choice between L&R balanced outputs on the stereo quarter-inch sockets, or (oddly) a TRS option which outputs on the Left out (only): tip L, ring R and sleeve Ground. Nice to have the option, but not convinced of the utility here!
I said earlier that you maybe wouldn't want to fill your rack up with a big many-HP mixer, but it seems 4MS have found a way of sneaking in simple but powerful (sub) mixer units by stealth. Their neat trick with the jumper leads means adding a second or even third mixer doesn't lose you front-panel inputs. The choice of 3.5mm or quarter-inch outputs is prescient, and the attendant IO and Listen Up modules really ramp up the options and functionality significantly. Maybe because the humble mixer is often relegated to the utility corner, there are not a huge amount of alternatives out there.
I think 4MS have really looked hard at what is required to open up the possibilities of a well-stocked rack and, in my mind, have justified the carving out of a small corner of your rack for some of these really, really useful mixers.
4ms Listen Four £189, Listen Four Quarters £189, Listen IO £113, Listen Up £65.
4ms Listen Four $189, Listen Four Quarters $209, Listen I/O $125, Listen Up $65.