Vintage MXR Pitch Transposer – FIXED!

May 11, 2016 6:11 pm Published by

The MXR Pitch Transposer – these weren’t used so much, most famously by Brian May apparently, not being a Queen aficionado I wouldn’t be able to tell you where… It does exactly what it says it does – transposes pitches. At first this might seem dull, anyone with logic will have messed around with Pitch Shifter, great for alien harmonies, desexing a voice, chipmunks, beefing up a line in subtle or non-subtle ways. This must have seemed quite amazing in the 80’s without having to slow/speed tape. It has 4 knobs that transpose pitch to just over an octave either way, presets that you can flip between by simply touch-activating (earthing) the corresponding knob, this is a very effective and sensitive interface. It seems strangely unique

However don’t be fooled, this is more than a transposer, it makes some of the most mind boggling effects I’ve heard. I’m reminded of DMT experiences of shattering the fabric of time , there is a REGEN (REGENERATION) knob that creates trailing, alien type sounds, especially good when you flip between presets. I don’t think you will ever encounter a parameter called ‘Regen’ in other effects units, apart from MXR of this period.

The history of the ‘regeneration’ parameter is interesting, apparently derived from old radios where the output was fed back into the input of itself to make it more sensitive.

It’s a bit like the much mythologised Eventide Harmoniser famously introduced by Tony Visconti to Eno and Bowie, as ‘fucking with the fabric of time’, except it doesn’t have the same detail over the time-based (regency) stuff. Thing is, those things are going for a bomb these days, you’d never be able to find one, or afford it if you did. The great thing is that Universal Audio have come out with a plugin for £189, not cheap, but it’s meant to be great

Listening to that snare on Bowie’s Breaking Glass, this is definitely an effect you can make with the MXR. I picked this one up from Eddie down the corridor, who used to play drums with Alabama 3, he sold it with the display module that takes up an additional 1u rack space, so it takes up 3 in total, which seems excessive, but even looking at the PCB’s, they’re telling of a culture less obsessed with minimising space. It was working intermittently for a while before completely going kaput. I deduced it must be something to do with the MIX pot, as twiddling all the way to ‘Effect’ would cut out the sound. So the problem could only be in the Pot or more profoundly with the effect circuit itself, but the first step was to test the pot and connections to the board.

Removing the enclosure was entirely straight forward the 2 side panels unscrew, inside there are 2 layers of PCB, the first easily unplugs and detaches from little plastic nipples. After detaching the main PCB from the enclosure in a similar way I was able to get underneath the PCB and to the connections on the board. Using my tester I deduced the pot itself was working fine, offering variable resistance as it should. However there were gaps around some of the solder joints – so called ‘dry solder’ where over time flux from the solder corrodes and eventually causes the connection to fail. Looking at it, it had definitely been soldered by hand, I guess on some kind of production line by exploited Americans in the 80’s, Jon Bon on the stereo, perhaps this worker had been lost in day-dreams of mullet-cladded orgies when he/she missed the solder on this connection.


Hallelujah! A simple re-solder and the unit is fixed. I also spied that the plug that makes the knobs touch sensitive wasn’t pushed in correctly, the ‘BYPASS’ button had never worked, now it does and the unit is fully functioning – just like in the days of  May!  The main caution here is that all the wires have got very brittle over time, it seems like they could break quite easily… so careful when poking around in there kids.

Back in the rack.

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