From roberts@pharm.sunysb.edu Fri Nov 14 19:33:20 1997 Return-Path: by taz.hyperreal.org with SMTP; 14 Nov 1997 19:33:17 -0000 14 Nov 97 14:32:54 -0500 From: "Roy Roberts" Organization: Pharmacology, SUNY Stony Brook Date: Fri, 14 Nov 1997 14:32:16 -0500 Subject: (Fwd) Review: Kenton MIDI kit for Korg PS-3100 Priority: normal X-mailer: Pegasus Mail for Windows (v2.54) ------- Forwarded Message Follows ------- Date: Thu, 13 Nov 1997 23:45:55 -0500 (EST) From: Tony Clark Synth-DIY Subject: Review: Kenton MIDI kit for Korg PS-3100 After a long and restless waiting period, I finally received the schematics to this beast (thanks Mark!) and was able to finish installing the MIDI kit for this wonderful synth. WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING This kit is definately NOT for the novice. WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING Now that is out of the way, let's get started: First, I'm going to get a disclaimer out of the way. The guys at Kenton are a good bunch of chaps, they have been helpful with my questions and understand some of the issues I brought up. Having said that, I'm going to put it bluntly. The installation instructions aren't much of a help at all. The reason? It was written for the PS-3300 which is (from what I've discerned) totally different in every way than the PS-3100! So all of their diagrams didn't help a bit. So anyone thinking of attempting this job better have the schematics and a good DMM. And, BTW, Korg doesn't have any manuals for these machines, quoting the service tech, "You do know how OLD these synths are don't you?" Anyway, that problem past, the first step to getting the MIDI kit installed is to mount the circuit boards. Can anyone confirm that the PS-3300 is deeper than the PS3100? The instructions show mounting the circuit board assembly on top of the large card cage, but due to the way the PS-3100 is built, it would stick two inches out the backside of the cabinet! So this posed problem #1. Solution: Remove all of the synth cards (9 total). The left three card upper/lower socket sets have to be moved to the left. This gave me enough room to mount the MIDI board against the center metal dividing panel. And to do this, I had to widen the holes in the upper part of the metal dividing panel to accept machine screws. Now I was able to fasten the MIDI board to the dividing panel. Use a rubber bumper (included in the kit) to prevent the MIDI board from hitting the dividing panel. Now came some of the fun part. Connecting up wires. The power supply was no problem. One thing to watch is the multitude of different voltages that it puts out. The PS-3100 has no less than 5 different voltage feeds. Two +/- 15V rails with one +/- being diode protected (use these to power the circuitry) and a 10V rail for the panel. The MIDI kit comes with two huge ribbons that are used to trigger the different keys. The PS-3100 has a 48 note keyboard and so there are 48 wires to solder. This is where the PS-3100 differs from the PS-3300. On the PS-3100 there are 4 gate cards (each controlling one octave). The ribbons must be split into groups of 12 (it actually doesn't work out that nicely) and connected to the correct gate card. No existing wires are removed. Kind of a symbiotic relationship. The unused parts of the ribbon cable can be clipped off. Next comes wiring on the small analog board. The one thing I disliked immensely about the MIDI kit was that the analog signals were to be routed to a box that sits piggyback on the backside of the synth. This box has 6 1/8" jacks, one pushbutton, and the MIDI IN and THRU. Here's my thing, first, the pushbutton for entering in MIDI setup mode is on the backside of the unit. Not a very convenient place to put it EVEN if you don't end up utilizing it much. Second, I'd have to have special patch cables to use AND they'd be wrapping around from the back to the front of the synth. Unacceptable. Instead, I decided to use the wonderful aspect of the PS-3100 and it's bretheren. Patchability. First, I disconnected the two controller inputs (Really, does anyone own a Korg controller??) and rewired them as my MIDI IN and THRU (damn convenient if I must say so). I drilled a hole just above these two sockets and mounted the pushbutton in it. Now I can easily access the MIDI setup at any time. Now there is an analog board that comes with the MIDI kit and I had to mount this on the front side of the card cage utilizing two of the many holes along the top side. After mounting this board, I had to figure out my strategy for connecting in the 6 lines (Pitch bend, Modulation wheel, Aftertouch, MIDI Cont. 7 (volume), Cont. 16 (filter), Cont. 17 (resonance)). Obviously the Pitch bend line can be routed directly to the wheel on the PS-3100. The Mod wheel and aftertouch lines I decided would be best routed to the controller 1 & 2 inputs (which I disconnected the DIN sockets but not the 1/4" jacks). Cont. 7 goes to control VCA2, Cont. 16 goes to control filter cutoff. But instead of routing Cont. 17 to the triple resonant filter, I decided instead to divert it to control the frequency of the Sample & Hold function (more on this later). In order to fully implement the above, I put together a small circuit board with 4 non-inverting amplifiers (of the TL082 kind) with two inputs each. Now I could disconnect and redirect signals so that all of the original controls were left fully functional only with the added MIDI control. With things wired in this manner, I can now patch the Pitch Bend, Mod. Wheel, and Aftertouch to any of the other patchable parameters on the PS-3100! And although the Mod. Wheel and Aftertouch use the voltage processors, this can be overridden by patching directly into the voltage processor inputs. The filter and volume MIDI controls can't be overridden but are there to allow some programmability via a sequencer program. And you're probably wondering why I dedicated a MIDI control line for the S&H frequency...well...it was because of all the things they made patchable on the PS-3100, this was the one thing they left out! It was there BEGGING to be connected in. Really you could just drill a hole and mount a 1/4" jack there and have a patchable frequency control (maybe one of these days I'll do just that). But in any case, this is something I'd make use of. And as the triple resonant filter already has a patchable filter control, I can easily patch in the Pitch bend, Mod. Wheel, or Aftertouch to control it via MIDI. How does it work? Pretty good, I must say. I haven't fiddled around with most of the MIDI setup stuff, but setting MIDI channels and transposing works well. Overall, I would have preferred Kenton to have made a smaller MIDI board and worked on a better installation guide (for which they are in the process of going through and redoing a number of them). Unfortunately I doubt much will be done with the electronics as I was told they'd only sold a grand total of "3" PS-3100/3300 MIDI kits. Oh well, I'm not going to complain, I've got a very cool synth that will neatly fit into my MIDI setup now. Now if only I can solve the massive noise issue of the PS-3100 and the crosstalk, I'll be a very happy man... Tony -----------------------------------,---------------------------------- I can't drive (my Moog) 55! | -----------------------------------| The E-Music DIY Archive Tony Clark -- clark@andrews.edu | COMING SOON! http://aupe.phys.andrews.edu/~clark| -----------------------------------'---------------------------------- Roberts@pharm.som.sunysb.edu