Doepfer

To do this looks relatively straightforward. The PA381 is a current 
output device: the currents output from pins 1 & 7 of both chips all 
come together at one end of J1, and are summed by one op amp in the 
TL082 - pin 6 is the summing junction, pin 7 the o/p, pin 5 grounded. 
So you would have to replicate this op amp set-up - a 47k feedback 
resistor, 22p stability cap (C13) and 1k o/p resistor - for each 
section. The second op amp in the TL082 is unused, but it would 
probably be easier to use a TL084 on a separate piece of 
stripboard/whatever.

It's getting late in the UK, but I can maybe supply more help 
tomorrow if needed!

Tim

--- In Doepfer_a100@yahoogroups.com, "danv_83" <danv_83@y...> wrote:
>
> Hi,
> 
> I was just playing around with the a-135.
> 
> I basically want to be able to make seperate outputs for each 
channel
> after the cv attenuator circuitry. I am having trouble figuring out
> exactly how the circuit works - I was thinking that the final stage
> before each channel's signal get summed and then led through the
> makeup gain ic and then to the master out - is on the pa 381 ic. So 
my
> plan was to just tap the seperate outputs from the two pa381 ic's 
and
> then lead each channel into it's own seperate makeup gain opamp,,,, 
> 
> So I tried this but wasn't getting any signal.... I'm sure if I 
could
> see the schematics I could make better sense of everything,,,, 
anyhow
> I am hoping somoene can offer some insight on how to actually do 
this.
> 
> It would be great to have the seperate outs,,, would be like have an
> extra 4 vca's available!
> 
> Thank You!
>