The Mighty Home Made Synth

I vaguely know this fella, we're Facebook friends. 
https://www.macbethstudiosystems.com/

Also had chats with Analogue Solutions in the past - 
http://analoguesolutions.com/

Oh yes, having recently built a very nice Accutronics brick - based reverb pedal, I'm going to modify the design to work at synth voltage levels.  More and more retro redesign synths are coming with onboard effects now, so !!! I think I'll join the club. 

The more observant amongst you may notice that I made a boo boo on that board and soldered 12 resistors and capacitors the wrong way around. They're next to the DAC chips and are acting as a high pass, not low pass, filter. 

The moral of the story is (a) never solder with the flu and (b) always check the schematic. ;-)

Update. All coming along, just very slowly !!!

Well, since last posting here, the Home Made Synth has made some very slow progress, mainly due to me soldering everything in sight and going off in 26 other directions. 

Story so far. 

We have the power. Well. 400 milliamps of it, in the form of a linear PSU in Eurorack format. This is OK for development at the moment. To be upgraded. I'm going to design and build a more powerful PSU later. It's in Eurorack format, so the synth basically runs on 12v. 

We have a MIDI to CV interface. This was easy, I bought a kit. ;-) MIDI goes in the MIDI plug and out it goes to the oscillators, more of which below. I have no intention of designing a MIDI to CV interface when there are any number of good ones out there on the market. 

Oscillators, we have a basic design and some (reissue) Curtis CEM3340 chips. The 3340 was a great design as it offered internal temperature control, lots of waveform outputs, basically, it was a complete oscillator in a chip. However. As Jupiters and Oberheims started being replaced by digital synths, the Curtis range of chips dissapeared, but, huzza and hats thrown in the air, they're being reissued. So guess what I'm using. Two or three, to be decided. Chips are in the post. 

Sub oscillators - make a synth sound bigger and more useful by adding sub oscs, which add a base note either one or two octaves below the original note. These are going to be multi waveform as well. So there's interesting, look you. 

All the waveform outputs and the sub oscillator outputs go into a mixer, so you've got massive variation of sound. More bang for little buck. 

This leads us to the filter. I'm going to use a 24Db Moog ladder design (knee jerk filter decision) and I've got some prototyping to do. I had a load of old obsolete Soviet matched pair transistors lying around in DIP-8 format. So they're going in the parts pile. Should be interesting, the filter will benefit from a lot of playing around with, so that's a whole new fish of kettles. 

That's it so far. I've got plans for a couple of illuminated moving needle VU meters on the output stage. Anyone say "retro" ? and most likely some kind of inbuilt PT2399 based echo. That's not a lot of design work and more a case of using voltage dividers to get down to guitar pedal levels. There's more to do, in terms of low frequency oscillators and envelope generators for the VCA and VCF, but it's coming along. Oh yes. Going to put a CV generator in which does very slow control voltage loops. Should be interesting. 

And I decided that this will be a fully normalised design. Saves on sockets and cables. ;-)))))

Watch this (outer) space, pics to follow, just don't wait up. ;-)))))

For panel design, there's a great free tool at 

The 3D board viewer I use is at

http://3dbrdviewer.cytec.bg/

Drag and drop an Eagle board file onto it. It makes a heroic effort to render your board in 3D, but has a limited number of components in the library. Useful for guessing clearances and seeing if something will actually be "solderable" in real life.

Wow, I didn't realise you could get PCBs made like that . I once made a fuzz box and an "electronic drum" with resonant circuits from a book on home electronic projects in music, but neither were very good .

If it all comes together, and that's some way off, I think the design is going to resemble an original MS-20. 

Well.

Got a modular sequencer, home built.
Nearly finished a dual audio generator.