Doepfer

> hi,
>
> thanks for the responses.
>
> the vco's tracking seems to be fine, i connected the pitch cv to it
> without the a170 and everything was accurate over several octaves.
>
> the patch yesterday had the output of the slew limiter - the upper
> section, by the way - going to two destinations. i reduced this to a
> single connection to the vco's cv1 input. this removed some of the
> voltage drop, so that i'm able to compensate with the tune offset (so
> no more brass parts). however, each octave is about 20 cents flat -
> not really a huge problem with one octave, but with three octaves i'm
> more than a quarter tone flat.
>
> i don't have the precision adder, so i can't try out that solution.
>
> does noone else have this? i tried it with three a170's - i discovered
> another one in the drums rack which i`d forgotten :) - and got the
> same result. i'm not particularly sensitive about intonation, i like
> it dirty, but  a quarter tone is, well, TOO dirty :)
>
> stu

I'm quite sure that it's a problem with the output protection resistor in
the A-170. It's the 1k resistor R2 just above the printing "A-170" on the pc
board. The A-100 modules are designed in a way that they cannot be damaged
even with "wrong" patches (e.g. connecting two A-170 outputs). For this
nearly each output is protected by a 1k resistor. This resistor prevents
module damage even in case of patches that could destroy modules (especially
if two outputs are connected by mistake). You could short the 1k resistor R2
e.g. by a wire. I'm wuite sure the tuning problems will disappear then. But
the A-170 output is no longer 100% protected. As long as usual patches are
made this will not be a problem. But if you e.g. modify two A-170 in this
way and connect the outputs they will be damaged.

The better solution is the usage of the A-185-1 or A-185-2 as they have
special output circuits. But even shortening R2 will help as long as only
this single A-170 is modified in this way.

Best wishes
Dieter Doepfer