Miscellaneous DIY Projects

- Polyphonic CV & Gate inputs for Korg Mono/Poly

I'm not sure if anyone has ever done this before. After scouring the Mono/Poly schematics, I located 4 points where I could insert 4 (buffered) external CV signals to control each of the VCO's.

Check out my CV-input schematics:

1. CV Insert Points
2. CV Buffers and Input Jacks

The four gate inputs were much trickier, because you not only have to send a trigger signal to each of the VCO chips, but also to the lone amplitude EG. I used a MOS4071 -OR- gate to sum each of the incoming triggers in addition to the internal trigger bus. I buffered the external gate signals (of course) with another TL084.

The Mono/Poly can now be simultaneously triggered internally and externally. Fun!

(Pics of the actual modified synth coming soon)

- Midified Jen SX-1000

Silly me - I thought this would be an easy project... just find the spot to inject a CV and gate signal. Well, that's fine and good except for the fact the the SX-1000 uses a strange Italian DCO chip made by SGS. Despite it having voltage controlled tuning and LFO inputs, I wasn't going to get the range I wanted. Not to mention, the keyboard tracking would be rendered useless because it was controlled by the DCO chip.

Good old MIDIbox came to the rescue: I built a Core and Digital Out board and then tried using some 2N3904 transitors to trigger each of the keys. No dice.

I took a chance and ordered some MOS Photo-relay chips for 0,15 euro each and connected them to the MIDIbox DOUT board. It worked great! Now each key is triggered by a photo relay chip.

- Nord Micro Modular inside a Yamaha RS7000

I don't like carrying a lot of equipment when I perform. Actually, I do carry a lot - so this is a lie of sorts. Anywhow, at some point I decided that my Nord Micro Modular was too heavy (hahah) and so I stuck it inside my Yamaha RS7000.

Wait - that's crazy!

- PFL Modification to UB-802

When I perform, I often need to cue up material before bringing it in the mix. Unfortunately most compact mixers don't offer a PFL on the AUX Send, so I modified a cheap little UB-802 to do the job. It's now been deprecated in favour of a Roland M-10DX digital mixer.

View schematics for PFL-mod.