Doepfer

> Hello,
>
> Curious about the new version of A-132-3.  On the page for the A-132-4 it
> says that at 0V it only attenuates -60db.  Is this true for the 132-3 as
> well, or is there negative offset built into the pc board?
>
> Thanks,
> Monroe

It's different for the linear and exponential mode. In the linear mode the
max. attenuation is much less than -60dB. In the exponential mode one never
reaches -00 dB (infinite) in theory as in the exponential mode a certain
voltage difference corresponds to an attenuation in dB (e.g. -10dB/V or
20dB/V). In reality of course the signal disappears in the noise floor if
the attenuation exceeds a certain value. We tried and discussed several
control scales for the exponential mode of the new SSM2164 based VCAs. If
the control scale is flat (e.g. -10dB/V) one obtains a smooth attenuation
but the min. attentuation is limited unless a negative voltage is applied.
If the control scale is steeper (e.g. -20dB/V) a min. attenuation close to
zero is reached (e.g. -100dB for 5V range). But in this case the attenuation
comes very fast (-20dB or 1/10 at 80% of full scale, -40dB or 1/100 at
60%, -60dB or 1/1000 at 40%, -80dB or 1/10000 at 20%). So one has to find a
compromise between min. attenuation and control scale. The new exponential
VCAs (A-132-3 in exp. mode and A-132-4) have about -12V/dB which is a good
compromise from our point of view. But it would be possible to change the
scale by changing some resistors on board.

Best wishes
Dieter Doepfer
(Back from holiday)