Hi Paul,

> my A-131 exponential VCA was bought in September 1998 (no idea when

it

> was built. PCB says it´s a version 2 from 1996).
> It also uses the PA382. (the other two ICs are Texas Instruments´

TL062)

Same as my A-130, so hopefully I can clarify...

> Look on the PCB (frontplate facing to the left):
> -below the PA382 you can read: LIN:3381 LOG:3382
> The module overview of my owner´s manual (NOT the service manual)

says

> "...built with CEM3381 / 3382"
> So is the PA382 the same chip as the CEM3382 but with another name

Or

> is it a totally different IC Dieter, please help!

I'm quite sure that the PA381=CEM3381, and PA382=CEM3382. Since the
datasheet I have for the PA381/2 is published by OnChip Systems, who
I believe brought the rights/mask sets to make the Curtis chips, I'm
assuming the 'CEM' designation ('Curtis Electro Music') is the old
one, and that OnChip renamed them to use the 'PA' designation.

> another look on the PCB:
> -above the PA382 I can find a blank field marked "ST2" with ten

solder

> points (actually that´s two pairs of five solder points marked: + /
> ground symbol / triangle symbol / CV / - )
> -to the lower right of the PA382 there´s a solder point

marked "JOUT /

> BOARD 2" .
> Florian, you said that you can modify the A-130/131 into two VCAs

when

> they use CEM chips. Is it then possible with my VCA with these

solder

> points

Yes. Basically the 10-way connector feeds out +/-12V supplies,
ground, and connectios to the gain, input and output pins of the
unused vca section in the chip. Thus you would need to provide some
circuitry to control the gain, and buffer the input and output. To
give some idea of whats involved for the used vca, with faceplate
held down, the left-hand TL062 provides the gain control, and one
half of the right-hand TL062 buffers the output, the other half sums
and buffers the inputs.

'JOUT/BOARD2' connects to the output of the vca section used on the
board, so I'm not quite sure what Doepfer may have had in mind for
its use on the mythical expansion 'board 2'. Notice also that
underneath there is an unmade link 'JCV' which would allow the unused
section to be controlled with the same gain signal as the used one.
Also not sure what the 'AUDIOSUM/J2' was intended for, since one side
is the summing point for the inputs, but curiously the other is just
ground. 'CVSUM/J1' is the same for the summing point of the gain CV
(the ground sides are marked with an upside-down 'T'.)

Not a trivial task, but certainly do-able with enough commitment and
application!

Tim