hello zoran,

yesterday i had just little time in the studio,
i haven't recorded anything, so please trust me :-)
anyway, i managed to compare an old and a new a131.
i tried sawtooth, triangle and sine after another,
coming from an a111. the a111 output was patched
directly into the vca in question. first i used
a constant +5v signal to keep the vca's open all time.
after trying this, i used an a140 envelope instead.

the newer a131 inputs are more sensitive, setting the
input attenuator to approximately 6.5 resulted in the
same loudness as with an old a131 set to 10.
i used this setting to check the hum of the vca's.

i found that the newer a131 (or at least mine) doesn't
produce more hum than the old one. maybe only a slight
nuance, barely noticeable, and not as horrible as in
your wav-files. you really need good ears to find
something like hum on my a131's and you have to search
for it until you hear it. that's why i couldn't really
understand your problem, until i heard your posted files.
your a131 doesn't sound like mine, absolutely not.
i don't have this issue on my a131's, no matter
if old or new. ok, the new a131 is louder when
it is unattenuated, sounding somewhat harsher then,
but still there is not that much hum.

i tried an a132 also and it sounded a bit smoother than
the a131, because it is linear. i'd say that our a132's
sound the same.

another funny thing is that my a133 polarizer produces
much more hum than any other vca in my system, even
when it isn't actually amplifying a signal and this
also makes me wonder. it kept me from buying another
polarizer yet, but maybe my a133 and your a131 have
the same problem

could it be that also other parts have been replaced
during the last few months maybe we can have some
information on this from dieter doepfer himself.
i hope that he is reading this.

best wishes

ingo