Harry's Rant was: Guitar synths (Don's rant)

[WeAreAs1 at aol.com]

In a message dated 5/20/00 8:02:35 PM, you wrote:

<<BTW, you mention a VCA in the GR-300.  Is this controllable in any way,
or is it simply linked to an envelope of the guitars natural decay?
There appears to be no controls for this anywhere.  It would be nice to
have a controllable attack for those "backwards" sounds.>>

Hello Paul,

I'll have to look again at the schematics to be sure, but I'm pretty sure 
there are six very simple FET-based VCA's (one for each string), that then 
feed into one common VCF.  These would be the ones you'd want to gain access 
to for the backwards sounds.  They are indeed controlled by the guitar's 
natural envelope.  Alternatively, you could insert another set of VCA's just 
after the FET's to do envelope effects (I would use LM13700's - you'd need 
three of them).  The GR-300 also has another VCA (based on a photocoupler) at 
the output section which is just there for master volume control.  The 
balance knob on your guitar is wired directly to this VCA.  I'm pretty sure 
that if you plug in a volume pedal, it gets routed to this VCA.  Now that I'm 
thinking about it, I remember that there's also another photocoupler VCA for 
the straight guitar signal, as well. (both are controlled by the guitar's 
volume and balance knobs, and are not affected by your picking intensity or 
the note's envelope)

The very rare GR-33B bass synth from the same era used the same technology, 
and it had both attack and decay knobs, unlike the GR-300's decay-only setup. 
 I guess they figured the funk bass players would want to use it to make 
those "duck quack" funk synth bass lines, a la Mutron III.  It would be 
fairly easy to adapt the attack envelope portion of the GR-33's circuitry to 
the GR-300.  I'm pretty sure the GR-33B attack/decay envelope was monophonic 
(not a separate envelope for each string), and it was manily for controlling 
the filter, not the VCA.

The G-808's two touch switches were simply there to turn the GR-300's LFO 
modulation on and off (one switch had a latching on/off alternating action; th
e other was on while you touched it, off when you took your finger away).  If 
your Ibanez doesn't have a modulation on/off switch, you may have never even 
heard the GR-300's LFO in action.  Definitely a useful tool.  You wouldn't 
need the touch switches on the guitar - you could always make a footswitch to 
control it. (personally, I find the touch switches kind of awkward to use)

BTW, you could always build a hex fuzz into your Ibanez, or into the body of 
the GR-300 module.  Seven opamps, twelve diodes, and handful of resistors is 
all it would take.

Michael Bacich