Hi Zoran,

> Why Because I have just returned noisy A-131 (creates distortion

on any

> setting, not only above 7), just to receive brand new A-131 that

behaves

> almost the same (noise not as loud, but STILL there).

Florian has already pointed out the differences in the chips from old
to new - there are other things that affect the behaviour here too.

Assuming the component values in the A-131 are still the same as mine
(it's marked v2, 2001), then the resistor values around the CA3080
which set the gains in the 131 and the 132 are quite different,
making it much easier to drive the 3080 in the 131 into its non-
linear area of operation, causing distortion, which is also likely to
be contributing to what you hear. (If I remember from previous posts
on this topic, Dieter has said this is deliberate.)

You seem to have tried reducing the level of the input, which should
reduce these effects - are you also aware that 'In2' is more
sensitive than 'In1' That is (if you haven't already tried it), if
you are using In2, try it on In1 instead (and vary the setting) to
see if this makes much difference.

In theory it should be a relatively simple matter to replace about 3
or 4 resistors in the 131 to make it more like the 132 (albeit with
the log scaling), which has the potential to reduce this distortion
effect. I'll have a more detailed look at this tonight (I have more
resources at my disposal now compared to when I looked at this last,
18 months or so ago.)

Also if you are driving the 131 from a 140, if the CV2 setting is too
high (above about 6 or 7) you don't get the full 'range' of the
envelope, the top gets flattened off (this shouldn't cause distortion
at all, but will affect the overall shape of the sound).

Tim