PROJECT: BiMix




Notes
So, having made one Eurorack module, I thought I’d push it for two. There’s a very active DIY element in the modular synth world, with their own sub-forum on Muff-Wiggler, sharing a plethora of designs, PCBs and panels. The main filter I have in my system is a Malekko/Wiard Boogie filter, an intriguing beast of a 4 pole filter mixing elements of Buchla and Moog flavours. One thing about this filter is it’s flexibility – and with a bi-polar mixer on board, it’s possible to this machine unpack a plethora of low pass, high pass, band pass and other filter types through mixing the each of the filter outputs in different ways.

I have a small case for my modular synth, and dream of keeping it that way, and there are not many compact commercial offerings for bi-polar mixers... So, courtesy of theabsent, a madly impressive man from Finland, who has built a monster DIY modular, offered a kit called the BiMix – three channels, with an offset on channel one, in a neat little 4hp package.

My first challenge was finding potentiometers that would fit the bill – the standard 16mm potentiometers that are readily available the world over are too big to fit behind the tiny panel. A quick query on the MuffWiggler DIY forum directed me to a couple of German websites – I picked mine up from MusicDing in the end, and got the 9mm Alpha pots needed (and some other bits and bobs too, as it would be rude not too...).

The build itself looked relatively straight forward after the Thomas White Resonant Low Pass Gate, and probably took about 90 minutes for me to assemble. The soldering practice to date is evidently making me confident, and therefore quicker, tho I still don’t get along with my Maplin Temperature Controlled soldering iron, which just loves oxidising. I’m going to pick up and Antex one and see if it’s any better (there appear to be many complaints on the web about the quality of the soldering bits that the Maplin iron uses, so I’m blaming that).






So, build completed quite quickly, but no noise at the other end on plugging it in. And I noticed one of the IC’s getting quite hot, which I’m sure wasn’t in the design. Now, theabsent is a charming man, but the thread on MuffWigglermade clear this was a kit for the capable, and no support was offered. In some trepidation, I dropped him a message, explaining my woes, and he told me to send him pictures of both sides of the board. Within two minutes of sending said pics, he’d come and said ‘You left the bloody jumpers off!’ (more or less). I felt like a dolt, having done this repeatedly on the Dual LPG build, but two little jumpers added in, and the mixer works like a treat. The only other bit that stumped my was the holes for the jack sockets on the board were wider than the nuts on jacks I had – so improvised with washers, and all good. Would probably have used the sometimes maligned Cliff jacks if they’d been readily available, as they’d look neater, but it doesn’t impede usability, so happy enough to add this one to the case. A very handy little utility. Now, I just have to start trying out some of the various Boogie flavours the BiMix opens up.

Results Pass


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