Hi Self oscillate,

I don't have one of these, but from it's description I'd guess the
audio input gets split into two paths: one through an amplifier and
filter for the treble boost, and then out; the other presumably
splits off after the treble boost to go through another filter doing
the voiced/unvoiced detection, which then switches the other inputs
and supplies the gate. It sounds like something in the audio path has
got screwed up in some way, which is what is giving way too much
amplification, and hence distortion. Turning the input signal down
externally would then alleviate this, but would also probably give
the voiced/unvoiced detection some difficulty, which seems to fit
your symptoms.

> the a129/5 worked well for years.
> do i have to replace it or is there a chance of getting it repaired
> unfortunately dieter doepfer is at the namm show,
> so i'm not getting really helpful advices from doepfer.

It's probably fixable (it could even be as simple as replacing a
chip). Whether you will need to get it back to your local distributor
(and perhaps then back to Doepfer), or can get someone locally to do
it I don't know, depends on where you are I guess (in the UK the guy
who runs EMIS does some repairs himself, which is obviously quicker
than sending it all the way back to Germany...)

Tim