This used to happen on my ARP 2600 VCA and was a DC offset problem.
Happily there was a straightforward calibration solution accessed
with a small screwdriver through a tiny hole in the front panel and
explained in detail in the manual.
I have a few of the old CEM based A-131 and a couple of RS-180 VCAs
used with various different mixer/amp/ouput scenarios and never had a
thump problem from these.
Sounds very much like a calibration issue - you really don't want to
have to compromise your ADSR times or start filtering unnecessarily
just to get a decent response from your VCA. Hopefully there's a
simple solution.
Sean
>I believe this is solely due to your amp. I have experienced this
>with several devices, including RS180 (ASys), A132-1, A132-3, ASol
>SY01, and even the RS100 filter, if I just modify the amplitude (or
>cutoff frequency) with a gate or a fast envelope. Maybe it's just
>because you and I have cheap amplifiers, or maybe it's just inherent
>to the voltage levels of modular synths (and their rates of change).
>But I think slowing down the envelope time is the only cure.
>
>Anyone with a nice amplifier or monitor have an opinion
>
>Monroe
>
>On Fri, Feb 20, 2009 at 10:34 PM, mirror_saw7778
><<mailto:haven1%40gmail.com>
haven1@...
> wrote:
>> I have a pair of 132-3 VCAs and love them except one thing which is
>> making me sad. When I control them with a 143-2 ADSR they make a low
>> "thump" sound. This sound happens regardless of input signal volume or
>> frequency. the sound actually makes nice kicks ;) but makes a mess or
>> my delayed arpeggio patches.
>>
>> The VCAs are in exp mode. the only way I can make it go away is to use
>> a slower attack on the ADSR. the only other VCA I have tried is a Asol
>> SY02 which does not "thump". the SY02 is not DC coupled AFAIk.
>>
>> I have the ADSR and the VCA's in separate G6 racks.
>>
>> any suggestions could this be DC offset due to ground issues I do
>> have a furman power conditioner on the AC.
>>
>>
>
>
>
[Non-text portions of this message have been removed]