Doepfer

Hi,

I just found on the doepfer page  http://www.doepfer.de/a1324.htm

Does it make senst to make this VCA exponential, if it does not offer an 
offset?

To make it clear: VCAs without an offset are mostly usable for real 
overall signal control only, like the classic "loudness" envelope to the 
final VCA. It basically has to be clear, that there is a standard 
situation "no signal at all" ( = "note off" at the classic synth structure).
Most other use cases like AM of audio or velocity control of signals 
etc. pp. have the standard situation "some signal has to pass", which 
means an offset voltage must control the VCA and this offset control 
must be adjusted always to the corresponding control signal amount.


Now: The mentioned standard situation of VCAs without offset uses 
envelopes as CV. But envelopes do not need exponential VCAs. The CV 
itself has already an exponential characteristic.


So to my opinion is:
if this VCA is intended to be exponential it misses a onboard standard 
offset (without that it is useless for exponential use)
if this VCA is intended to have no onboard standard offset, then it 
should be linear.
But as it is planned now, it is "neither fish nor fowl".

Florian

> Hi,
>
> I just found on the doepfer page  http://www.doepfer.de/a1324.htm
>
> Does it make senst to make this VCA exponential, if it does not offer an
> offset?
>
> To make it clear: VCAs without an offset are mostly usable for real
> overall signal control only, like the classic "loudness" envelope to the
> final VCA. It basically has to be clear, that there is a standard
> situation "no signal at all" ( = "note off" at the classic synth
> structure).
> Most other use cases like AM of audio or velocity control of signals
> etc. pp. have the standard situation "some signal has to pass", which
> means an offset voltage must control the VCA and this offset control
> must be adjusted always to the corresponding control signal amount.
>
>
> Now: The mentioned standard situation of VCAs without offset uses
> envelopes as CV. But envelopes do not need exponential VCAs. The CV
> itself has already an exponential characteristic.
>
>
> So to my opinion is:
> if this VCA is intended to be exponential it misses a onboard standard
> offset (without that it is useless for exponential use)
> if this VCA is intended to have no onboard standard offset, then it
> should be linear.
> But as it is planned now, it is "neither fish nor fowl".
>
> Florian

Florian,

I'm sorry but the A-132-4 is already in production and we expect the first
batch of modules about end of April. Since we announced the A-132-4 about
half a year ago (see the corresponsing messages around October 03, 2009 in
the group) nobody recommended to add an offset nor any other modification.
To my mind customers tend to have small an compact modules. Adding an offset
would we possible for a "Mark II" version of the module and increase both
price and width. From my point of view an offset should be combined with an
attenuator for the CV input. This leads to a totally different module with
all controls like the A-132-3. The A-132-4 is just what is says: a compact
and affordable exponential quad VCA. If offset and CV attenuators are
required the A-183-2 could be added or another VCA module should be used.
I do not agree that the double exponential shape (envelope and VCA control
scale) cannot be combined. Though I'm not an practicing musician any more I
used very often the exponential VCA A-131 in combination with the A-140 ADSR
(rather than the linear A-130) to obtain snappier sounds.

Best wishes
Dieter Doepfer

Don't we all own A176 modules to provide for the offset?
I see double CV inputs...
That's how I go about it on the A132-1. (which is not exponential I know!)


grtz

Ernst






On Tue, Apr 13, 2010 at 11:41 AM, Florian Anwander <fanwander@mnet-online.de
> wrote:

> Hi,
>
> I just found on the doepfer page  http://www.doepfer.de/a1324.htm
>
> Does it make senst to make this VCA exponential, if it does not offer an
> offset?
>
> To make it clear: VCAs without an offset are mostly usable for real
> overall signal control only, like the classic "loudness" envelope to the
> final VCA. It basically has to be clear, that there is a standard
> situation "no signal at all" ( = "note off" at the classic synth
> structure).
> Most other use cases like AM of audio or velocity control of signals
> etc. pp. have the standard situation "some signal has to pass", which
> means an offset voltage must control the VCA and this offset control
> must be adjusted always to the corresponding control signal amount.
>
>
> Now: The mentioned standard situation of VCAs without offset uses
> envelopes as CV. But envelopes do not need exponential VCAs. The CV
> itself has already an exponential characteristic.
>
>
> So to my opinion is:
> if this VCA is intended to be exponential it misses a onboard standard
> offset (without that it is useless for exponential use)
> if this VCA is intended to have no onboard standard offset, then it
> should be linear.
> But as it is planned now, it is "neither fish nor fowl".
>
> Florian
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>


[Non-text portions of this message have been removed]

surely it would make sense to offer a quad vca in both exponential and linear versions? i would certainly rather see a version b with linear charactaristic than with a bunch of knobs :)

stu

(sorry, hit return too early)

i'm a big van of these smaller utility modules - the only thing i like more than reducing costs is reducing width! and for patches with four voice polyphony, these modules really are a godsend, and my drum patch rack will also benefit from the upcoming quad modules (although i think the quad decay envelope would have been better as a slew limiter, allowing dynamic control as well).

so i'll be ordering several quad vca's as it is, but i'd also be interested in a couple of linear versions too.

> (sorry, hit return too early)
>
> i'm a big van of these smaller utility modules - the only thing i
> like more than reducing costs is reducing width! and for patches
> with four voice polyphony, these modules really are a godsend,
> and my drum patch rack will also benefit from the upcoming quad
> modules (although i think the quad decay envelope would have been
> better as a slew limiter, allowing dynamic control as well).
>
> so i'll be ordering several quad vca's as it is, but i'd also be
> interested in a couple of linear versions too.

Unfortunately all currently available high quality VCA circuits (THAT,
SSM2164 and similar) have an exponential control scale. We still have linear
VCAs with good quality in stock (e.g. CEM3381) but as they are no longer in
production we do not want to start a development with obsolete circuits.
Converting an exponential VCA into a linear one is not that easy because a
exp/lin converter is required. One could use another of the same VCAs to
obtain this function but this would require 2 VCA circuits (one for the VCA,
one for the exp/lin converter) to obtain one VCA. Of course OTAs (CA3080,
LM13700) could be used - as used in some of the existing VCA modules (A-130,
A-131, A-132-1) but the audio quality is not as good as for the THAT/SSM
circuits. We want to use only these high end VCAs in all new designs.

Best wishes
Dieter Doepfer

Hello

> one for the exp/lin converter) to obtain one VCA. Of course OTAs (CA3080,
> LM13700) could be used - as used in some of the existing VCA modules (A-130,
> A-131, A-132-1) but the audio quality is not as good as for the THAT/SSM
> circuits. We want to use only these high end VCAs in all new designs.
OK, then I'll stay with the original A132.

Florian

> > one for the exp/lin converter) to obtain one VCA. Of course
> OTAs (CA3080,
> > LM13700) could be used - as used in some of the existing VCA
> modules (A-130,
> > A-131, A-132-1) but the audio quality is not as good as for the THAT/SSM
> > circuits. We want to use only these high end VCAs in all new designs.
> OK, then I'll stay with the original A132.
>
> Florian

Good idea. A quad linear VCA based on the A-132 circuit (OTA) would not be
much smaller or much cheaper that two A-132-1. Only if we find an affordable
solution to offer a linear quad VCA with higher audio quality it makes sense
to start the design of such a module.

Dieter

Do I understand the way normalizing is used in this module correctly:  that one could input one audio source in In 1, and up to four CV sources to differentially distribute that audio source out of the four Outs?  And conversely, one CV source to control the amplitude of up to four different audio sources?  If so, that seems hugely versatile....