Tascam MM-20
A six-input master module that asked you to build your own console - and quietly became the front door to four-track recording.
Overview
The MM-20 is not so much a mixer as the first brick of one. Tascam's System 20 concept, unveiled at the February NAMM Show in Los Angeles, treated a console as a set of modules you wire together, not a fixed chassis you buy whole. The MM-20 Master Module is the piece everything else hangs off. It has six inputs - a pair of transformer-isolated mic inputs on XLR and four line-level inputs - feeding four main outputs, a stereo auxiliary send, and separate monitor and headphone feeds. Tascam's own US marketing manager, Dave Oren, built the design philosophy around what the module lacks. He described the system's uniqueness as its absence of switches and the flexibility that results.
That absence is the point, and it will either delight or frustrate anyone who sits down at one. Instead of routing signals through dedicated switches to multitrack, monitor, foldback and echo sends, the MM-20 hands you the signal path at the relevant points and expects you to patch it yourself. Teac's stated rationale was that the unit should operate much like an electronic patchbay. For the solo artist-engineer working out of a spare room, one module can be reconfigured from a four-track tracking front end into a concert-sound desk into a submixer without buying a different console. For the engineer who wants a console to behave predictably, it means a fair amount of thinking before anything gets recorded.
Read the front panel closely. Mic inputs pan between outputs 1 and 2; the four line inputs sit between 3 and 4. Those designations are not track numbers - they can be used for anything - and one contemporary reviewer wished Teac had simply labelled them W, X, Y and Z to stop people assuming otherwise. In practice, a four-track session runs a pair of microphones (up to six with an EX-20 expander hooked in) through a PE-20 for EQ and pans them across outputs 1 and 2, with a row of phono sockets on the rear feeding the multitrack. Foldback comes off the stereo auxiliary busses A and B. Each input's aux section combines a level control with a pre-/post-fader selector and a pan knob.
The modularity is genuine. The EX-20 adds four more transformer-isolated mic inputs and a stereo auxiliary send. The PE-20 packs four identical channels of parametric EQ, designed to be inserted between the send and receive sockets on each MM-20 and EX-20 input. It offers three bands with up to 12dB of cut or boost. The low band is continuously variable from 60Hz to 1.5kHz and the mid from 1.5kHz to 8kHz, while the high band is fixed at 10kHz. The MU-20 meter unit houses four VU meters with peak-overload LEDs. Tascam pitched the whole thing at the home recordist: Modern Recording (April 1982, p.81) ran the MM-20 as "the heart and the start of a professional quality four-track recording system" in an advertisement promising a studio for under $400. That claim needs careful reading, since it refers to the entry point of the system rather than a complete working rig.
Owning an MM-20 costs more than the module. HiFi-Stereo (1983, p.118) listed the mixer at $1300, with a 15 V dc power supply, four VU meters, LED peak indicators, a built-in 4 x 2 monitor mixer, headphone amplifier, independent monitor switches and a variable input sensitivity selector. The chassis measures 18.25" wide by 20.5" deep by 6.3" high and weighs 35.4 lb. The same listing measured fader attenuation at greater than 60dB at the bus output, which is respectable headroom for a small-format desk. UK pricing was different again: a British review of the System 20 quoted £195 for the MM-20, £125 for the EX-20, £119 for the PE-20 and £85 for the MU-20, with the four units due in the country that July.
The modules bear a strong family resemblance to the Model 144 Portastudio - similar overall dimensions and weight, the same style of switches, knobs and faders. The resemblance is skin deep. The Portastudio is a self-contained cassette studio you can carry to a gig. The System 20 is a patchbay with faders, and Tascam designed it to be left permanently connected to as much outboard gear as possible. During overdubs the same pair of recording outputs gets reused, with previously recorded tracks coming back in on the line inputs and routed to monitor and foldback. At mixdown those four multitrack inputs land on the MM-20's four line inputs, which is why leaving them permanently patched makes sense. They stay available for monitoring and foldback all session, then become the mix path without a single cable move. Outputs 2 and 4 become the recording outputs feeding the mastering machine and meter bridge.
As a concert-sound mixer the module is more capable than its size suggests. A pair of mic inputs (more with EX-20s) and four line sources can be panned between four separate or combined main outputs and sent to auxiliary effects outputs, switchable pre- or post-fader, which double as on-stage monitor feeds. Outputs 1 and 2 from the mic channels can serve as subgroups and be combined with the final stereo house mix through a couple of line inputs. A combined master/monitor output buss with parallel foldback outputs can drive a mixdown machine, a PA, or control-room amps and speakers, or be routed through the MM-20's stereo headphone output.
The caveats come with the design. There are very few switches, which is fine until you cannot remember how you patched something three weeks ago. The fixed 10kHz high band on the PE-20 is a limitation for anyone used to sweeping the top end. The system also only makes sense as a system. An MM-20 on its own is a six-input front end with no EQ and no meters, and the cost of completing it climbs quickly past the advertised entry price. Expect the usual age-related service on a unit of this vintage. The module is heavy, the power supply is external at 15 V dc, and the rear phono sockets and edge connectors are the parts most likely to need attention.
None of that dims the appeal. The MM-20 is one of the clearest expressions of a particular early-Eighties idea — that a recording console should be assembled rather than purchased — and it remains a genuinely useful front end for a four-track setup, or a fascinating piece of modular design history for anyone who likes their gear to make them think. Collectors note that complete System 20 sets with the EX-20, PE-20 and MU-20 are considerably more useful than a lone master module, and pricing on the secondary market reflects that.
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