The feedthrough in VCA mode can be improved by removing the two 1M resistors
R13 and R14 (located below the two vactrols, color code brown-black-green).
These resistors are connected in parallel to the light depending resistors
(LDR) inside the vactrols to define the lowest frequency in VCF mode. In the
VCA mode they cause the feed through. We added these resistors as the
vactrols behave very different in the dark mode (no illumination, big
differences of the so-called "dark resistance") and could cause strange
effects in VCF mode at high resonance settings. But if one can live with
that disadvantage the two resistors can be removed (and re-installed if
desired). But I have to point out that a bit DIY experience is required to
re-install the resistors. Removing is very simple by cutting one of the
wires at each end of the resistor.

Best wishes
Dieter Doepfer

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto: Doepfer_a100@yahoogroups.com ]Im Auftrag von selfoscillate
> Gesendet: Freitag, 6. Mai 2005 07:45
> An: Doepfer_a100@yahoogroups.com
> Betreff: 1 a101-2 bleed in vca mode
>
>
> > also, 101-2 users, i understand that volume is not fully suppressed
> > in vca mode. about how much bleeds through just curious. it
> > seems like a really cool module.
>
>
> hello,
>
> yesterday i checked the bleed-through of the
> a101/2 lowpass gate in vca mode. well, there
> is a noticeable bleed-through in vca-mode, but
> not in the other two modes (lp and lp+vca).
> the bleed-through can be heard when the a101/2
> output is the only audible signal. this shouldn't
> happen too often in standard applications, but in
> certain cases it can be problematic of course, for
> example if you use a compressor afterwards.
> if such problems occour, i'd advise to use a noise gate
> or move over to a dedicated vca like a130 or a131.
> on the other hand the a101/2 has a very nice
> sonic quality and i use it in vca mode quite
> often, because the sound is so nice.
> but thats the deal with vactrols, they also
> have their disadvantages. technically the
> typical vca's like a130 and a131 are better,
> they respond faster, more exact and they can
> fully attenuate a signal. but sometimes the
> slow a101/2 is the better choice soundwise
> (my taste of course, others may disagree).
>
> in the following example i used a swept a110
> sawtooth wave at the lpg input.
>
> a101/2 settings:
> f/a = 0
> cv2 = 0
> lev = 3
> res = 0
> mode = vca
>
> then i used a gate signal coming from an a179
> at the cv1 input to open the lpg.
>
> http://www.selfoscillate.de/a100files/a101-2-bleed.mp3
>
> listening at normal volume you shouldn't hear too much
> of a bleed-through, but if you load the example into a
> wave editor and zoom in, you can see it. if you cut out
> the loud part of the recording and turn up the volume
> you can also hear it. you have to decide on your own if
> this is a problem. for me it is no problem at all.
> i mean, this is an analogue system and a bit of
> background noise is normal. in 99 % of all cases the
> bleed-through will be masked by other sounds and noises.
> in the end, nobody will notice it.
>
> best wishes
>
> ingo
>
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