To: analogue@hyperreal.com, (Analogue Mailing List)
From: Kyle Farrell orb@maxwell.ee.washington.edu,
cc:
Subject: Re: Roland SH-3a
Date: Fri, 21 Jul 1995 11:45:17 PDT

---

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 <colin@octavo.demon.co.uk>
Subject: For Brian Coates, Re: SH-3A
To: analogue heaven <analogue@magnus.acs.ohio-state.edu>

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.