TC Electronic M350 Processor

A quick look at the compact tc electronic M350 digital effects device.

The friendly guy in the brown truck dropped off some packages last Friday, one of which was a TC M350, which is positioned by TC as their lowest-end digital effects device (list price $249). It’s a “dual engine” device, with one engine dedicated to non-reverb effects (like delay, flanging, chorus, phaser, tremolo and compression) and the second dedicated to reverb. It has two inputs, two outputs (all balanced, BTW), as well as S/PDIF digital I/O. It has a MIDI port for control, set-up dump and firmware update. A standard IEC jack attaches to the locale-specific power cord; the switch-mode power supply accepts any mains line voltage.

Natch, the first thing I do with any piece of gear is to open it up and poke around. Inside are two PCAs. One is a single-sided job that’s the power supply (it looks like TC buys somebody’s supply) providing +15V and -15V for the op-amps, +5V for the converters, and +3.3V for the digital stuff. The other PCA holds everything else. A Freescale (formerly Motorola) 56362-120 (about $8 in 1K qty) is the DSP, which is connected to an SRAM and a flash EPROM. Presumably, it’s clocked at 120 MHz (it has an internal oscillator and I didn’t check to see if the system clock is brought out to a port pin) so the DSP does 120 MIPs, which is obviously sufficient. Like all Moto 56K parts, it’s a fixed-point 24-bit processor, with a 24 x 24 MAC and 56-bit accumulators. An Atmel ATMega 8-bitter handles MIDI and user interface. The DAC and the ADC are AKM parts. Opamps are 5532s. Ferrites are used at all I/O ports for EMI suppression. I/O is balanced although it appears that the outputs use the simple build-out to ground for the inverting line (which is fine).

The M350 can be configured, via rear-panel switch, in one of two ways: One is as two parallel effects engines, with one input for the effects engine and the other for the reverb. In this mode, both engines have stereo out which are combined to drive the outputs. A balance control sets the relative level of both engines in the mix. The other configuration is serial, with the effects engine first, followed by the reverb engine.

I’ve been pretty vocal about my dislike of the dual-engine with one output configuration. It has to do with how I mix. I like to bring my effects into the console on their own inputs. I like to set up, on the input channel aux send knobs, the proper blend sending to an effect, while trying to keep the effect’s input level decently hot (best effect S/N), and then adjusting the level of the effect in the mix on the return fader. Usually the return fader lives somewhere other than at unity.

Having two effects combined in the box means you have to put the effects return faders at unity (or some other convenient level) and then establish the level of the effects in the mix on the effect input, which is a pain, perhaps less so if your console has faders for the aux send masters. Of course you’re boned if you want to use the box in the parallel mode but also send the delay output to the reverb (since vocal that’s fed to both a reverb and delay with the delay kept dry sounds kinda weird to me). So it’s a simple matter to say “this is a single-engine device,” especially since each engine’s effect select has an “off” position.

This brings up another important topic: User Interface. And the M350’s interface is kinda spartan, similar to competing products in its price range. There are the expected input-level and blend (wet/dry) knobs, and the effect balance knob.(There’s no output level knob, which is fine, as most users set it to maximum.)

Each engine has a 16-position effect-select switch (as noted, one position is “off”). The Delay/Effect engine has two pots for parameter adjustment and the Reverb engine has three such pots. The 12 o’clock position of each pot is what TC calls the “normal” setting. One could reasonably ask, “What’s normal?” For example, the Reverb engine has controls for Predelay, Decay Time and “Color.” If you choose the Gold Plate program, what’s the decay time? Seriously. At my show on Saturday, the opening band had a mixer-person, and he asked for a 2 second reverb. On many pro-level reverb boxes, the reverb decay setting is simple. On the M350 (and similar units from Lexicon and others, let’s be honest here), there’s simply no way to know your decay time.

And this is where the whole dual-engine-summed-into-one-output concept falls on its face: you can’t cue up just the reverb to fine-tune it… you also hear the delay engine. (Similarly, you can’t cue up just the delay without hearing reverb.)

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