From orb@maxwell.ee.washington.eduFri Jul 28 15:20:42 1995 Date: Fri, 21 Jul 1995 11:45:17 PDT From: Kyle Farrell To: Analogue Mailing List Subject: Re: Roland SH-3a Mike Kent wrote: > I would be cautious about puting this in rackmount. As far as I remember it > does not have CV/Gate inputs. Also, I think that the internal CV systm is > not linear like the older Rolands, So retrofit might be really tough. > Anyone else know different? > > Regards, > Mike. The SH3a is great! 2 LFOs (sin/square & sawtooth), thick VCO, not bad filter, sample & hold. Here is a message I saved from Colin Fraser regarding adding cv/gate inputs to the SH3a (I haven't actually tried this yet): Date: Tue, 31 Jan 1995 21:11:58 +0000 From: Colin Fraser Subject: For Brian Coates, Re: SH-3A To: analogue heaven Sorry to transmit this to the list but I can't get through to Brian direct... > I would > like info on whether this is a 1 v/oct synth or not, so I can calibrate it. > And also if anyone's put CV/Gate ins... It does have ins for VCF cutoff > and VCO, but I'm assuming these are for pedals. Thanks. I added inputs to my sh3a yesterday. The main problem is that the oscillator doesn't have any width control. The width (ie octave span) of the oscillator is controlled by a preset that adjusts the voltage at the top of the resistor chain on the keyboard. Rig up a variable gain op-amp in non-inverting mode to buffer the cv input and that should give you a usable cv input. The cv from the keyb is switched by a fet, located at the edge of one the pcb - one leg of this fet is soldered to a s/h capacitor lead and another transistor lead. The second transistor is part of the log to lin convertor (I think) - its glued to another identical transistor. De-solder these leads and connect your cv input to the leg of the glued transistor. Make it switchable if you still want to use the sampler section to provide oscillator cv's. BTW I have just bypassed the switching fet in my sh3a and connected the opamp output to the red wire that connects to the keyb. For the gate signal, the inner conductor in the purple wire to the keyb. must be connected to the sheild to trigger the envelope. The sheild is held at -15v, so I used a cny-17 opto isolator to act as an isolated switch for this input. Asciimatic below... 390R _____ 5v gate -----VVVVV----[ U ] 0v --------------[cny17]----- inner conductor [_____]----- sheild 100k preset Op amp to alter cv width: ___ __________________/ _ I>---- 0v I _____ \___I>-I I [ U ] ______I 22k ---[TL071]--- +15v I cv ------VVVVV------[ ]---------I-- output -15v--[_____] * Connect (-) input to wiper of 100k preset, one end of preset to 0v, other end to output. This is the width control. Start with the preset about half-way, and then adjust it until you get 1v=1 octave. The sh3a has a mellow sound and can make some good special effects. I don't think the filters sound anything like my sh09, probably since they are all discrete circuitry. I haven't played with the vcf and vco inputs yet so I cant comment on those. Peace Cf PS. > Searching through manuals for silly instructions. Here's a good one from the tb-303 manual... HOW TO USE THE .$./BACK BUTTON In case of correcting the mistaken sound, press the .$./BACK button after pressing the wrong key-switch. When pressing the .$./BACK button, one sound is back to before. (It is the condition of finishing writing one sound before the wrong sound), so you can re-write the right key-switch.