I’m slowly working towards a project, it’s still not ready to be disclosed though, but it needed a dual rail power supply. I’ve always bought Doepfer DIY kits for my Eurorack needs, but I needed a +14V/-14V for this project. Since I could use an extra +12V/-12V supply as well for future Eurorack work, I decided to build a power supply with variable voltage regulators so it could handle both.
I found myself short of an ADSR in my system and it annoyed me to no end I hadn’t thought of buying a few more. Instead of hitting the favourite Eurorack module dealer for my fix I went googling to see if I could cook up one of my own. Couldn’t be that difficult. Right. Turns out, there are tons of useful ADSR schematics floating around on the internet.
This is an envelop follower. Since I build an input module I kinda wished I had one of these so I made it a little project, fun for the whole family well, not really, but anyways..)
A very boring yet crucial part of any setup. A buffered multi always comes in handy and it’s pretty easy to build as well. Since I was building one myself I added a few leds to indicate signal and it’s polarity, that way I got some indication what’s going on. I used 2 separate leds since I didn’t have any dual coloured leds lying around. It would look a bit fancier with a dual led, maybe I should order a few, just in case I build a few more of these.
It shouldn’t be all weird stuff, sometimes one needs some simple building blocks. After a bit of experimenting with sending audio from the mixing desk to the modular I found myself short of a way to amplify a line level signal to the audio levels used in a modular. Hence, I thought I build myself an input module with the sole task to take in a line-level and give it a nice boost. It’s a simple module actually.
I’ve put some updated schematics for the oscillator one online. Changelog:
- Changed Linear Ramp output volume so it’s in line with the other ones (R59 to 20k instead of 10k)
- Changed the sensitivity of the coarse and fine knobs (R10 and R11)
- Used an LM4040 to create a 5V reference instead of L7805 and L7905 voltage regulator. I hope this will improve stability when switching octaves.
- Added a potentiometer for the saw animation in
I was one of those guitarists who spend more time with his effect pedals, then with his guitar. I ended up exchanging my guitar for synths when it came to music making. Not really a surprise there, but my love of piling effects together into a huge unpredictable pile is still there, and somehow, even with a bunch of 19″ racks I haven’t been able to scratch that itch. You could use a computer these days, but nothing beats a bunch of wires and noisy electronics to spark creativity. Guitar pedals are nice and all, but do lack in certain areas when you try to use them with synths.
While doing research for the oscillator I stumbled – seems to be a common theme — upon these IC’s. The ICL8038 promises to be a stable oscillator with very few external components. It’s an obsolete product, but I could get a few of them via Ali-express cheap enough to experiment with. Since it offers a sine output I immediately thought about doing some FM type percussion. That way I wouldn’t need 1/v per octave and pitch fluctuations wouldn’t be that much of a problem either. I also had a V2164 quad VCA chip around, so a 4 operators (aka oscillators) seemed a perfect fit. Enough to provide some interesting FM timbres at least.
Since Coolaudio started reissuing old IC’s used in various synths I always eyed the V3340, which is a reissue of the CEM3340 chip as used in many classic synths such as the Roland SH101, Prophet 5, Memory Moog and plenty of others. It’s, in essence, a fully featured 1V/oct oscillator on a single IC and thus takes away a lot of the headaches inherent to VCO design. Things like linearity and temperature compensating are taken care of for you. This takes away a lot of the pain of building VCO’s, in fact, since these IC’s are available again a DIY polysynth starts to become a possibility.
My ‘broken’ EHX Bass Micro Synth was gathering a ton of dust. After bringing it back to life I noticed all the sliders were far from performing well and should be replaced. Sourcing 10 100K linear sliders with the right dimensions turned out to be rather difficult and costly. So I decided to transplant the pedal’s guts into a 19″ rack casing from an old and broken M-Audio firewire audio interface and at the same time see how I could make it more synth/modular friendly. So, here’s a brief list of things I ended up doing to it:
- Switchable filter type (BP / LP)
- Added a square sub oscillator
- Added an external input
- Changed input/output gain behaviour
- Extended the filter range
- Added and ‘extra’ resonance switch
- Added external trigger input
- Added filter CV input
- Added Envelop follower CV output
- Added trigger output
- Added trigger/filterCV leds (the thing could use more leds)
- Added a sort of distortion/clipper
- Replaced the internal power supply with an external adapter (I really didn’t trust that thing)
So, it’s quite a list. But I’m pretty happy with the results so far. Things could do with a bit of tweaking here or there, but that’s up to personal taste. You’ll can find the schematics of the EHX Bass Micro Synth easily enough on the web, but for the lazy, click here. I’ll try to address the implementation of some mods in this article.