From E.Bruggeman@student.kun.nl Mon Dec 4 10:38:32 1995 Date: Mon, 04 Dec 95 15:56:32 GMT From: Ernest Bruggeman To: analogue@hyperreal.com Subject: 202 mod: VCF in Hi All Here's the modification for adding a CV input for the cutoff frequency. You can connect any device to this that delivers 0-5V for realtime control of the 202's filter. Examples: - a MIDI-2-CV box with CV connected to a MIDI controller - an audio signal (get some cool Richard D James kind of sounds.....) - the headphone out of the 202 itself (filter modulation with audio signal) - The 2nd channel of the 202 sequencer! Gets you cool S&H kind of VCF modulation. Or try slides. Wow! I believe it's similar to Koladich's (thanks, Scott!) 2nd channel VCF control, but I'm not sure. Anyway, here it goes, in my "best" English..... It's a step-by-step guide, so anyone (?) can do this. Total costs: $1 (add $1 for the beer and $1.50 for the letters) You need: 2 small wires, soldering iron, female mini jack connector additional: bottle of Heineken Export Beer, white rub-on letters (same font as on the 202) 1a. have the 202 in front of you, upside down, the connectors facing away from you. 1b. be sure to have a cold bottle of Heineken Export Beer somewhere near you 2. remove the screws (remember to keep them somewhere safe, I lost one of them) 3. flip over the bottom plate towards you. Watch out for the wires to the battery compartment, they're very short! I had to solder the black one again, as I broke it. My, this isn't a good starting. 4. Now we have to loacate the soldering points. First the ground: I think there are several potential soldering points for this, but I'll give you the point I used, as this one works for sure. If you look at the upper print plate, there are four large soldering points in a row. I used the fourth for connecting the ground wire. Connect the wire to the soldering side! 5. The more difficult part: locating the other point. I'll try to describe it, facing the board from the sodering side. Locate the point where the "tape save" connector is mounted to the board. It's on top (the side facing away from you) of the upper board. This connector is mounted using 3 relative large soldering places. Straight below them there are 2 small sodering points (part of a row with 7 points). Going down even further, there are another two small soldering points (most right 2 of a row with 9 points). Straight under this one there's another small soldering point (most left one of a row with 9 soldering points). Still following it? Now we're almost there! >From the last point I mentioned (the most left one of a row with 9 soldering points) go ONE soldering point to the right. The first point BELOW this one is the point we need! Solder a wire to this point. 6. You can verify if this point is the right one by using a multimeter: If moving the cutoff fader on the 202 the voltage on this point must change as well. (hey - now I understand why they call this VOLTAGE controlled filter...) BTW This is the way I initially discovered the connecting point: randomly measuring points while moving the cutoff slider till I hit the right point.....) 7. TEST if you've made the right connections! Program some notes into the 202's sequencer, put it into loop mode and add a 0-5V signal (example: CV out of any synth) to the wires you've just connected. (Watch out for polarity!) The cutoff frequency should change. You have to experience what's the best position of the cutoff slider when controlling externally. 8. OK, everything is working fine. Now you have to decide how you want to connect these wires to the outside world. You can use a 202 connector you never use, but I added an extra mini jack connection to the 202. There's *very* little space for an connectior at the back of the 202. Maybe the connector can go between the main out and the headphone out, or between the headphone out and the ext. synth gate. I'm afraid that behind the pre-drilled holes between the connectors and the sync connectors there's no t enough room.:-((((( (maybe after bending the resistors) You can also have the wires go outside via the battery compartment, no drilling needed this way. I added the mini jack connector to the RIGHT side of the 202's case, facing the 202 from the control panel. The ground wire goes to the ring part of the connector, the other wire to the tip. 9. Be careful when drilling holes in the 202 case. Use low rpm and steel drill 10. Now close the 202 case. 11. Drink your beer. Enjoy it. Relax. You deserve it. You're a winner. 12. You can add cool texts like "VCF in" or "Special Modification" with those write rub-on letters. Impress your friends! (after all, ain't that what tEcHnO d00dZ like to do?) NOTE: THIS MODIFICATION IS AT YOUR OWN RISK! I TAKE NO RESPONSIBILITY FOR IT OR FOR IT'S RESULTS. I'll unscrew my 101 soon and see why my ext. audio in doesn't distort, but actually sounds great. Report will follow if it's different to the one on AH archives..... Ernest Bruggeman (E.Bruggeman@student.kun.nl)