Tag Archive | Potentiometer

ProtoTypo PT5 – BUD666

While working on my ProtoTypo PT3 build I came to realize that actually just about any piece of Behringer audio gear would likely make a pretty neat candidate for hacking. I suppose that Behringer brands mostly as sort of entry-level hardware for the budget conscious. That is, anyone looking to get into audio production will often choose the least expensive entry point and grow up from there.

This reflects on Behringer resale value too, as people looking to “step up” want to off-load their (older generation) hardware to a market that’s constantly flooded by Behringer with the next generation gear (often carrying similar price tag with older gen). Why this is great for hacking is, it puts a ton of ‘source materials’ up for grabs at a very low price. Hacking a second-hand Behringer, say, to even see if it works usually doesn’t set you back much.. Even if you end up destroying the device in the process. Just remember to sort & recycle proper!

Take something like the 5€ DJ mixer (VMX100) that I hacked PT3 from: You’d be happy to get even half of new knobs for the same price (VMX100 has 13), add to that everything else like jacks, PSU etc! Looking at it from the electronics side, say, a basic opamp summing mixer is a basic opamp summing mixer regardless of whether it rolls off a Behringer or Focusrite production line. Using a basic functional block like this in a some other context then simply boils down to identifying it with the help of schematics or a some reverse-engineering.

Anyway TL;DR, I’m almost getting carried away so let’s cut to the chase!

Some months ago I spotted this second-hand Behringer HM300 guitar distortion pedal selling for 15€. I couldn’t help thinking “Well that’s a bargain, wonder if this would make a neat Eurorack module?”, and bought the pedal just to have a look. And so we end up with this build post!

I give you ProtoTypo PT5 aka BUD666 aka BUdget Distortion 666 :D

Why the 666? Well although I didn’t end up adding any extra features to the electronics, I still figured my hack has to be at least 2.22 times better than HM300!

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Klee, mech WIP

Work-in-progress teaser ;)

Sub panel starting to take shape.

Close-up of right edge, the home of all rotary potentiometers.

Klee, parts parts parts

As it turned out, Farnell UK wanted to sponsor my Klee project a little bit by hooking me up with some parts! Having gone through a good amount of sourcing for this project, this lead me to think about parts in general. As things are on hold anyway until I get the SP8T rotary switch, I might as well go through some of the items I’m planning to use..  Good news is, I do now have a source for the SP8T so I can soon shut up about it. Yay for that \o/

Image by Daniel Rutter

The boring shit

Anyone who’s into DIY electronics (or repairs) probably knows that selecting and sourcing all the bits & bobs needed can (more than often) prove bit of a headache.  Building up knowledge of reliable/usable parts sources takes time and any short-comings here can easily bring a project to a halt. Not that every shop stocks every single part you might need either.. Add things like specific part properties or plain ‘meh, done that already‘ to the mix, and you’re instantly in need of a wider shop selection.

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Matrix-12 control repairs

Once again, a repair documentation just for the sake of having these bits of info written down somewhere. Notebook as good as any ;) .. Just to intro this monster of a synth, here’s what Peter Forrest writes about it in his book “A-Z of Analogue Synthesizers“:

The Matrix-12 is a 61-note synth with three big LCDs, six value knobs and about 60 switches on the front panel. Internally, it is 12-voice polyphonic and 12-part multitimbral, each part responding to its own MIDI channel. Each voice provides two big fat VCOs (offering triangle, saw, pulse, and noise waveforms), one 15-mode VCF (offering various low pass, high pass, band pass, notch and phaser types, all complete with resonant squelch), five LFOs, five envelope generators, 15(!) VCAs, and one FM modulation generator for oscillator sync and cross-mod madness.

There’s also a lag generator (a sort of portamento that can be applied to anything, not just pitch), three keyboard-tracking generators, four ramp generators (a very simple two-level envelope) and, finally, one noise generator. And that’s just one voice. There are 12 inside here! All this sound-creating muscle is useless without an equally powerful control system, and to this end Oberheim came up with the ‘Modulation Matrix’ from which the machine takes its name. This system enables 20 connections per voice between virtually any parameters. For example, to increase the speed of an LFO with time, select LFO speed as the destination and a slow attacking envelope as the modulator.

The Matrix-12 that landed on my desk was in need of lever potentiometer and rotary encoder replacements. As is, the lever potentiometers had problems tracking smoothly (eg. resulting in pitch “warble”) whereas the encoders did a lot of skipping back and forth.. Working but unusable, so to say.

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