Minimoog sync circuit

[Konsult Niklas Lindberg]

Howdy AH:ers!

Just wanted to tell you I've finished the sync mod
(for the mini) I was talking about some time ago
(actually It's been finished for some time now,
just been to busy (read: lazy) to write).

Anyway it didn't turn out as easy as I first hoped. I
had to put in a little extra PCB inside the mini to
house the extra components (1 4066, 1 TL072 , 1 diode 
and some resistors).

In the beginning I was thinking of using the same
circuit as is used in the mini with a FET-transistor
in parallell with the charge/discharge cap, so I tried
with some FETs I had laying around; none of them worked!

So I started trying the other method: using a CMOS-switch
(4066) instead of a FET, and this worked perfectly!.

Later, when the switch circuit was already finished, I
finally found some specs for the FET used in the mini
(E112 I think) and I realized that none of the FETs I
tried was even close to the specs of the E112! So I
guess that it is possible to get that circuit working
if only you use FETs with the right specs. In that case,
it would probably be a much neater circuit than mine.

The circuit works as expected in all frequency ranges
except the uppermost (that is, when you put the controlling
osc. in the 2' mode) but I don't consider that a
problem since it isn't very usefull soundwise to use
syncing at those frequencies (you don't hear much difference
between sync/no sync).

To make the sync facility real useful though, I think one
will have to introduce the possibillity of separate
modulation of the controlled oscillators, to give a
constantly sweeping sound. This is quite easy I think,
but I haven't tested yet.

I haven't put the circuit into schematics of a readable
format yet, but if anyone's interrested I'll try to fix
that on the double.

/Niklas
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Niklas.Lindberg at ees.enator.se