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MXR Custom Audio Electronics MC403

Power Supply For Effects Pedals By Bob Thomas
Published July 2012

The burgeoning numbers of boutique pedal builders and the availability of Velcro probably means that, despite the availability of low‑cost digital multi‑effects units, the future of the pedalboard is secure. Pedalboards, though, have always had a problem that has never quite been overcome: power, the requirements of which usually result in unsightly mains extensions populated by wall‑warts.

MXR Custom Audio Electronics MC403Riding to the rescue is the latest collaboration between Bob Bradshaw and MXR, the MC403 Power System. This device is housed in a hefty, no‑nonsense, white‑legended black metal box that exudes an air of invulnerability. One end carries the IEC AC mains inlet and a parallel out and one side carries all the low‑voltage outputs and the power on/off switch. The outputs are arranged as mirror‑imaged pairs so, starting at the mid‑point and moving to the outside, there are (on either side) one output that is adjustable anywhere from 6.5 to 15 Volts DC, four 9VDC outputs, two 18VDC and one 9VAC, giving a total of 16 outputs. All DC connectors are centre-negative and all DC outputs are completely isolated, regulated, current‑limited, over‑voltage limited and carry short‑circuit protection.

Opening up the MC403 reveals that it actually contains two separate power supplies, which are not the same. I'd expected the circuitry to be laid out differently to accommodate the mirror‑image connectors, but what I didn't expect was that the two toroidal mains transformers are constructed differently, to accommodate the requirements of the unit's wiring loom.

Included with the MC403 are a 19‑inch rack front panel and two pedalboard brackets (plus 12 screws) that allow you to locate it either in a rack or on your pedalboard. You'll also find 20 cables that should cover most of your requirements, unless you need a centre-positive connection, in which case you'll have to build your own or order one from the Dunlop Custom Shop.

The manual lists a comprehensive selection of the pedals, by brand and model, that can be powered by this supply, and this list should enable you to determine if your pedal collection will benefit, and to identify any additional adaptor leads that you may have to source. Having done your homework, all that remains is to plug up the relevant power leads between the MC403 and your pedals, and switch on.

In the interest of trying to produce some abnormal reaction, I loaded up all the outputs of one half and short‑circuited a couple, at which point all the other pedals carried on working perfectly. Once I'd removed the shorts, everything worked normally once again. At that point I gave up trying to break the MC403 and moved onto playing with the variable DC outputs, whose primary purpose, in addition to giving you access to 12 or 15VDC, is to emulate the effect of using a partially discharged battery. Some players find that a dying battery, especially a zinc-carbon one, gives certain transistor‑based distortion/fuzz/overdrive pedals a tone that they find attractive, and the adjustable output allows you to experiment with this effect.

The MXR Custom Audio Electronics MC403 is built like the proverbial tank, seems impervious to misuse and should continue to supply voltages to any pedals connected to it for the forseeable future. The provision of mounting brackets and a mains AC pass‑through socket make it easy to integrate into your setup.

There's really nothing to fault, and any decision to buy an MC403 will be down to your requirements for effects pedal power. The price may be a point of protest (it's the RRP given below — the 'street' price is considerably lower), but the MC403 is beautifully built, does precisely what it's designed to do and will no doubt carry on doing it for a very, very long time, so if you need one it's great value. If you're contemplating a big pedalboard and need a power supply, this is probably one of the best solutions available. You'll know when you need it. Bob Thomas

£329 including VAT.