Date: Tue, 30 Jun 1998 10:00:38 -0400 (EDT) From: Andrew Schrock To: map@cs.washington.edu Subject: Re: more 202 mods Hey Mike, A quick update to the 202 mods I sent you: The 5vdc line to the switch of the accent mod should have a small value resistor (25-50 ohms) in series with it. The problem was that the 202 goes slightly out of tune when you draw directly off the 5vdc line. This fixes the problem. Andrew | Andrew Schrock | | Network Programmer, Synthesizer and electronic music enthusiast | | aschrock@cs.brandeis.edu | Date: Fri, 26 Jun 1998 12:46:13 -0400 (EDT) From: Andrew Schrock To: map@cs.washington.edu Subject: more 202 mods Hey Mike: here are 2 mods I did last night which might interest somebody. Both of these mods are by Andrew Schrock (aschrock@cs.brandeis.edu). Distribute and copy as you please, email me if you find any errors or have any questions. I made these because they're fun to twiddle in the middle of a sequence, and they allow for a variety of variations when you're twiddling a single loop. They don't really change drastically the sound of the unit, but instead extend its functionality a bit. They are not for the faint-hearted: the interior of the 202 is pretty cramped, and there's not a lot of room for error. Obviously do these mods at your own risk; I'm not responsible for you frying your synth. I have skipped the obvious instructions on how to take the 202 apart since it's pretty self-evident. Accent always on switch: (separate for VCA-always-on/sequencer-only/VCF+VCA-always-on) Ingredients: wire, dpdt center off switch, solder. Drill a hole in your 202 wherever looks good for the switch. (make sure there's enough room below to accomodate the switch without touching the pc board or any components!) Find the main CPU chip, it should have something like PD78C06 written on it. It has 64 pins and is fairly large. (it's on the solder side, not the component side) Locate pins 39 and 40. (hint: find pin 1 by locating the circular mark on the lower-left side of the chip and count up counter-clockwise from there.) You want to be able to alternately switch these pins "high" (up to +5vdc) when you flip a switch. The problem is that you can't have _just_ a VCF accent; [altho if you put the VCA on gate only you bypass the VCA accent altogether] you also have to have the VCA accent high. So when you put the VCF trigger high you also have to put the VCA trigger high. I like to have a separate switch for the VCA only to be high as well. Note that this will bypass whatever you've programmed into the sequencer for accent. If you hook a dpdt center-off switch up as follows, the 1st switch will put the VCF and VCA high, making them both accented; the 2nd switch is both off, which will have only sequencer-induced accent (just like before it's modified); the 3rd switch puts just the VCA accent high, making just the VCA accented. I find that these mods are handy for live performance and twiddling. The VCA-on switch overdrives the filter at max resonance, giving a very 303-esque sound.. it's nice to put a few random notes on accent and then when the filter gets really frenetic flip on the accent-on switch. .------. to 39-------| | to 40-------| | | |-. 5vdc--------| | |-----=\ 5vdc--------| | |-----=/ | |-. to 40-------| | ---| | .------. Portamento always on switch: Ingredients: 1 spst switch, wire, solder. Drill a hole in your 202 wherever you want the switch to be. (make sure there's enough room below to accomodate the switch without it touching the pc board!) Cut the trace coming from pin 38 and attach one side of the trace to the middle of the switch, the other side of the trace to the other side of the switch. (thus making it so that you can bypass the trace at will) This will make the portamento switch low, which engages the portamento. You can now use the portamento on every note whenever you want. Note that this will bypass the sequencer-induced portamento when switched on. .------. to 38-------| | | | to other side | |-. of 38-------| | |-----=\ | | |-----=/ | |-. | | -------| | .------. If you wanted to be really fancy, you could use a spdt center-off switch and attach a not-gate to the extra pole so that the portamento is _inverted_ from what the sequencer outputs. (thus non-portamento'd notes get portamento'd) The center off would disconnect the trace entirely and the other pole would allow normal-mode sequencer portamento, just like the regular mod. Andrew | Andrew Schrock | | Network Programmer, Synthesizer and electronic music enthusiast | | aschrock@cs.brandeis.edu |