Doepfer

Do the A-14x EGs feature logarithmic, linear or exponential response curve of the segment voltage function?
I wonder especially for the A-143-1

Best, Diego

Hi!

> Do the A-14x EGs feature logarithmic, linear or exponential response curve of the segment voltage function?
> I wonder especially for the A-143-1

I'm *guessing* linear, as you can make them control a VCA that can be switched between linear and exponential (e.g. A-132-3), and I'm guessing the VCA is converting the linear input into an exponential one or leaving it alone based on the setting, rather than the other way around.  I'm not sure, but that would be my best guess, if no one else is answering. :)

Aren't exponential and logarithmic essentially the same thing? I'm pretty sure they are, as in, you use a logarithmic graph to more easily depict an exponential curve.  So a signal's either adding the same amount each time (linear) or doubling it (exponential).

It's times like this I really want to set aside some time to study maths, heh...

Hope that helps,
Zoë.

> Aren't exponential and logarithmic essentially the same thing? I'm pretty sure they are, as in, you use a logarithmic graph to more easily depict an exponential curve. So a signal's either adding the same amount each time (linear) or doubling it (exponential).

The are as similarly "same" to each other than multiplication and
dividison are to each other. It depends which variable you are
considering in relation to the other.

In my opinion, when generating frequencies, it's better to call it
exponential, since the output is exponential in relation to the input.
And it's more natural to describe functions as the output they are
generating. (In math the function and its output are often
exchangeable in discussion.)

- Ville Oikarinen

Hello

Am 25.11.2016 um 01:15 schrieb diegora@free.fr [Doepfer_a100]:
> Do the A-14x EGs feature logarithmic, linear or exponential response curve of the segment voltage function?
> I wonder especially for the A-143-1
They are exponential (for log-vs-exp see Ville Oikarinens comment).

It is quite difficult (but not impossible) to create linear envelopes 
with an analogue circuit, but it is dead simple to create an exponential 
envelope.

Take as a basic princible: you have usually always a controlling source 
(example: Envelope or LFO) and a controlled destination (example: VCA, 
VCF). To get a linear increase of the recognized behaviour, always 
combine an exponential part with a linear part. Means:

Use a linear VCA with analogue envelopes (because the envelope is 
exponential).
Use an exponential VCA with an LFO (because the LFO is always linear).


Florian

Greetings and thanks to everybody for the feedback. 
I indeed referred to the Make Noise Maths panel control which gradually moves from log-->linear-->exp for a given AR envelope, cycled or not. As far as I can “listen”, I find that they are not very much the same, surely not in musical terms. Probably the specular/opposite, in the sense that the segments are bended in the opposite direction curves and upside down…one way for the first segment, the other way for the second, and this probably matches with the multiplication/division ratio mentioned above (?). As for the A-143-1, the graphical marks show curved segments for Attack (rises faster in the second portion) and Decay (falls faster in the first portion). Especially the attack slope sounds more expressive and naturally picking than the one performed on an A-140. So I thought there must be a huge difference in the design between the two EG. 


Another open matter to me is the possibility to take advantage of the velocity out on the Doepfer MIDI interfaces. Many users adopt the gate only to open the vca. I tried to fire velocity cv into the TipTop EZ4000 Deviater input with non enthusiastic results. I wonder if possible to have it to control a second cv input on a vca. It's not that common. Maybe the new Doepfer quad vca might respond properly to both gate and velocity, having 2 cv input jacks? Or would the exp character of an EG soon saturate into an exp VCA? 


Best, Diego 






Il giorno 25/nov/2016, alle ore 14:46, "Florian Anwander fanwander@mnet-online.de [Doepfer_a100]" < Doepfer_a100@yahoogroups.com > ha scritto: 







Hello 

Am 25.11.2016 um 01:15 schrieb diegora@free.fr [Doepfer_a100]: 
> Do the A-14x EGs feature logarithmic, linear or exponential response curve of the segment voltage function? 
> I wonder especially for the A-143-1 
They are exponential (for log-vs-exp see Ville Oikarinens comment). 

It is quite difficult (but not impossible) to create linear envelopes 
with an analogue circuit, but it is dead simple to create an exponential 
envelope. 

Take as a basic princible: you have usually always a controlling source 
(example: Envelope or LFO) and a controlled destination (example: VCA, 
VCF). To get a linear increase of the recognized behaviour, always 
combine an exponential part with a linear part. Means: 

Use a linear VCA with analogue envelopes (because the envelope is 
exponential). 
Use an exponential VCA with an LFO (because the LFO is always linear). 

Florian

Hi

Am 25.11.2016 um 16:33 schrieb diegora@free.fr [Doepfer_a100]:
> As for the A-143-1, the graphical marks show curved
> segments for Attack (rises faster in the second portion) and Decay
> (falls faster in the first portion). Especially the attack slope sounds
> more expressive and naturally picking than the one performed on an
> A-140. So I thought there must be a huge difference in the design
> between the two EG.
Nope. There isn't any difference in the characteristic of the 
attackphase. This is psychoacoustic: you hear what you want to hear.
Electrically the type of the envelope circuit (loading / unloading a 
capacitor) is completely the same on both modules.


> Another open matter to me is the possibility to take advantage of the
> velocity out on the Doepfer MIDI interfaces. Many users adopt the gate
> only to open the vca. I tried to fire velocity cv into the TipTop
> EZ4000 Deviater input with non enthusiastic results. I wonder if
> possible to have it to control a second cv input on a vca. It's not that
> common. Maybe the new Doepfer quad vca might respond properly to both
> gate and velocity, having 2 cv input jacks? Or would the exp character
> of an EG soon saturate into an exp VCA?
The correct patch of a velocity voltage for a velocity controlled 
signal-level is like this:

You need one exp-VCA and one lin-VCA

The VCO-signal is sent to the signal-in of the lin-VCA and the 
signal-out of the lin-VCA is the outputsignal

The envelope (any Doepfer envelope) is sent to the signal-in of the 
exp-VCA, the signal-out of this exp-VCA is sent to the control-input of 
the lin-VCA which carries the audio signal.

The velocity voltage from your interface is connected to the 
control-input of the exp-VCA which handles the level of the envelope.


Florian

Florian, thanks for focusing on the characteristics of Doepfer EGs attack slope… 


I see what you mean by psychoacoustics, though I did believe that those audible differences are real rather than consequences of individual perception. 


As for the velocity to modulate amplitude besides gated envelopes, do you mean that the velocity voltage and EG voltages should be mixed together and the sum sent to the unique VCA control input? If I am correctly following, I believed that this way they would mutually affect the result of each other. That's why I was thinking to rely on a 2 cv inputs VCA, one for the average amplitude (velocity) for each gate, the latter for more detailed amplitude “drawings”… Maybe it would be just the same result... 



Best, Diego 





Il giorno 25/nov/2016, alle ore 17:35, Florian Anwander fanwander@mnet-online.de [Doepfer_a100] < Doepfer_a100@yahoogroups.com > ha scritto: 







Hi 

Am 25.11.2016 um 16:33 schrieb diegora@free.fr [Doepfer_a100]: 
> As for the A-143-1, the graphical marks show curved 
> segments for Attack (rises faster in the second portion) and Decay 
> (falls faster in the first portion). Especially the attack slope sounds 
> more expressive and naturally picking than the one performed on an 
> A-140. So I thought there must be a huge difference in the design 
> between the two EG. 
Nope. There isn't any difference in the characteristic of the 
attackphase. This is psychoacoustic: you hear what you want to hear. 
Electrically the type of the envelope circuit (loading / unloading a 
capacitor) is completely the same on both modules. 

> Another open matter to me is the possibility to take advantage of the 
> velocity out on the Doepfer MIDI interfaces. Many users adopt the gate 
> only to open the vca. I tried to fire velocity cv into the TipTop 
> EZ4000 Deviater input with non enthusiastic results. I wonder if 
> possible to have it to control a second cv input on a vca. It's not that 
> common. Maybe the new Doepfer quad vca might respond properly to both 
> gate and velocity, having 2 cv input jacks? Or would the exp character 
> of an EG soon saturate into an exp VCA? 
The correct patch of a velocity voltage for a velocity controlled 
signal-level is like this: 

You need one exp-VCA and one lin-VCA 

The VCO-signal is sent to the signal-in of the lin-VCA and the 
signal-out of the lin-VCA is the outputsignal 

The envelope (any Doepfer envelope) is sent to the signal-in of the 
exp-VCA, the signal-out of this exp-VCA is sent to the control-input of 
the lin-VCA which carries the audio signal. 

The velocity voltage from your interface is connected to the 
control-input of the exp-VCA which handles the level of the envelope. 

Florian

Florian, I see that the second possibility would mean also to spare a VCA (which are never enough), though I still believe that it would be necessary to adopt a VCA with «two» cv inputs, that is to have two control voltage inputs on the VCA module in order to modulate the amplitude through both EG and velocity voltages. Or there's a step I missed in the understanding of the patch? Maybe you just intended to mix the two signals... 


Best, Diego 



Il giorno 25/nov/2016, alle ore 21:14, "Florian Anwander fanwander@mnet-online.de [Doepfer_a100]" < Doepfer_a100@yahoogroups.com > ha scritto: 







Hello Diego 

On 25.11.16 20:25 , diegora@free.fr [Doepfer_a100] wrote: 
<blockquote>




As for the velocity to modulate amplitude besides gated envelopes, do you mean that the velocity voltage and EG voltages should be mixed together and the sum sent to the unique VCA control input? If I am correctly following, I believed that this way they would mutually affect the result of each other. That's why I was thinking to rely on a 2 cv inputs VCA, one for the average amplitude (velocity) for each gate, the latter for more detailed amplitude “drawings”… Maybe it would be just the same result... 


if you mix the velocity voltage with the envelope voltage and feed the sum into one VCA, it will cause the VCA all the time a little bit (according to the velocity voltage) and the evnelope will add on top of this basic level. 

You have two possibilities: 
1.) Use the envelope and a first VCA, as you do it always, and then add a second VCA after the first one which is controlled by the velocity. 
2.) send the envelopes voltage through a VCA, and control this VCA by the velocity voltage. The result will be an envelope voltage whose amount depends on the velocity. With this modulated voltage you can control again the audio VCA as you are used to do. 
The advantage of solution 2: you send the audiosignal only through one VCA, which will be better for the audiosignal. 

Florian 



 
</blockquote>

Hi Florian, thank you very much for the patience, the support is much appreciated!

My issue to grasp depends on different 'subjective' factors among which prevails the lack of electronics basic principles. :-)

Then I got confused because in one of the previous messages of yours, before mentioning the 2 possibilities for using Vel and EG, you patiently tried to follow my proposal of mixing Vel+EG, but the core phrase you wrote missed the essential “verb” and so I still don't know exactly what really would entail mixing Vel+EG:

«if you mix the velocity voltage with the envelope voltage and feed the sum into one VCA, it will cause the VCA all the time a little bit (according to the velocity voltage) and the evnelope will add on top of this basic level.»

Anyway, now I see I always need to adopt 2 VCAs, probably (I try to guess again) the better quality VCA will preferably manage the audio signal (and here I can choose to fire the velocity OR the EG). 

Another subject which probably crosses this application is the difference between linear and exp VCA. Sorry, I won't you to go back to the lin/exp dilemma of the EG segments :-) but if EGs segments are always exp (because it's easier to design), then probably wouldn't be that wise to have an amp which features exp control scales, it might be redundant. It seems that linear VCAs finally are more versatile...

As for the AC-coupled / DC-coupled thing, I really understood very little when I tried to go wiki. I only got that there are advantages and disadvantages in both ways of coupling. I just acritically rely on the assumption that a vca having DC-coupled ins/outs is suitable for better processing both audio and voltage signals, and that is also preferable that voltage signals are processed by linear VCAs. Don't know if there's a relationship between AC or DC coupling and Exp or Lin response, probably not at all..

One last thing: why do we found some VCA's who offer 2 CV Ins if they cannot be used to process EG + Velocity? Do the 2 inputs affect the amp in the same way or they are wired to different stages?

I was interested in this quad VCA, what do you think about it?

https://www.modulargrid.net/e/doepfer-a-132-4

Thanks a lot !

Best regards,
Diego



----- Mail original -----
De: "Florian Anwander fanwander@mnet-online.de [Doepfer_a100]" <Doepfer_a100@yahoogroups.com>
À: "Doepfer a100" <Doepfer_a100@yahoogroups.com>
Envoyé: Dimanche 27 Novembre 2016 19:57:27
Objet: Re: [Doepfer_a100] A-14x EG segment slopes






On 26.11.16 19:09 , diegora@free.fr [Doepfer_a100] wrote: 


though I still believe that it would be necessary to adopt a VCA with «two» cv inputs, that is to have two control voltage inputs on the VCA module in order to modulate the amplitude through both EG and velocity voltages. Or there's a step I missed in the understanding of the patch? Maybe you just intended to mix the two signals... 
You still miss something. You always MUST have two VCAs to use velocity on the signal level. It does not matter, whether the velocity controlled VCA works DC coupled and manages the level of the envelope or whether it works AC coupled and manages the level of the audiosignal. 

You may have a look at 
http://www.doepfer.de/a100_man/A132_man.pdf 
page 4, left example 

Florian

> Electrically the type of the envelope circuit (loading / unloading a
> capacitor) is completely the same on both modules.

That's correct. But the switchover point (i.e. where the attack ends and the
decay begins) is another parameter which is normally fixed in envelope
generators. If this level is smaller only the lower section of the loading
curve is used for the attack. If it's higher more of the asymptotic share
(where the voltage converges to the max. capacitor value) of the curve is
used. I have considered to add this as an additional parameter to an
envelope generator but then rejected this idea because changing this
parameter also affects the maximal envelope level and the attack time. It's
very difficult to compensate this with analog circuitry.

Best wishes
Dieter Doepfer

Hello Diego

Am 28.11.2016 um 00:36 schrieb diegora@free.fr [Doepfer_a100]:
> but the core
> phrase you wrote missed the essential “verb”
You are right. Sorry for that

> «if you mix the velocity voltage with the envelope voltage and feed
> the sum into one VCA, it will cause the VCA all the time a little bit
> (according to the velocity voltage) and the evnelope will add on top
> of this basic level.»

This should read "...it will cause the VCA to let the signal through all 
the time a little bit...".


The important thing is, to remember that MIDI-control and 
voltage-control work different:

The MIDI-system is event orientated. This means: the event Note-On tells 
the note value and the velocity value. It is not the job of the 
MIDI-Keyboard to keep up this information. The receiver has to compute 
and remember the status until the next event is received.

The CV/Gate-system is status orientated. This means: in a CV-system the 
sender of the information (let it be the keyboard or the MIDI-interface) 
has to deliver continuosly the information about the actual status. The 
receiver does not have to care about it, he can rely that the sender 
provides the status all the time.



Now back to the velocity topic.

Lets take an example:

We switch on the complete system. All voltages, let it be pitch / 
velocity / gate, are 0 Volt.


 From the MIDI-keyboard an noteOn event comes to the MIDI interface. 
This event says: "Note D#1 has been pressed with 50% velocity".

The MIDI-Interface will translate this to
* Pitch-voltage = 1.32 Volt (I'm not sure 1.32 is the right value for 
D#1, but it does not matter in this case)
* Velocity-voltage = 2.5 Volt (assuming the velocity voltages cover 0 to 
5 Volts)
* Gate-voltage = 5V (assuming gate is 0V/+5V)

The next event will say: "Note D#1 has been released".

Now the MIDI-Interface will change only the gate-voltage back to 0 
Volts, but the pitch and velocity voltage will remain:
* Pitch-voltage = 1,32 Volt
* Velocity-voltage = 2,5 Volt
* Gate-voltage = 0V

Now let us assume, we have used an organ-like envelope at the ADSR (this 
makes it easier to calculate the voltages, because we can simply use the 
gate-voltage as envelope). If we add the envelope-voltage and the 
velocity-voltage, then we would get a voltage of 7.5 Volt at the noteOn 
(2.5V velocity + 5V envelope). At the noteOff event we would get a 
voltage of 2.5 Volt (2.5V velocity + 0V envelope).

If you feed this to the audio-VCAs control input, then the VCA still 
would send some signal through continuously after the noteOff.




> Anyway, now I see I always need to adopt 2 VCAs, probably (I try to
> guess again) the better quality VCA will preferably manage the audio
> signal (and here I can choose to fire the velocity OR the EG).
Right.


> Another subject which probably crosses this application is the
> difference between linear and exp VCA. Sorry, I won't you to go back
> to the lin/exp dilemma of the EG segments :-) but if EGs segments are
> always exp (because it's easier to design), then probably wouldn't be
> that wise to have an amp which features exp control scales, it might
> be redundant. It seems that linear VCAs finally are more
> versatile...
As written before: our hearing expects exponential changes signal 
levels. So you always need one exponential part in the game.
As you have both, linear voltages (velocity or LFOs) and exponential 
voltages (envelopes), you need both types of VCAs in your system. But I 
tend to have more linear VCAs than exponential ones.

> As for the AC-coupled / DC-coupled thing, I really understood very
> little when I tried to go wiki.
Basically everything works fine with DC-coupled VCAs, but one might get 
some "whumppp"-sounds at immediate noteOns, if you use a DC-coupled VCA 
with an audiosignal that contains a DC-offset (example: unsymmetric 
pulse wave).

> One last thing: why do we found some VCA's who offer 2 CV Ins if they
> cannot be used to process EG + Velocity? Do the 2 inputs affect the
> amp in the same way or they are wired to different stages?
Example: if you want to control the overall level of a voice with 
velocity and with an slight amplitude modulation, then you may do that 
with the mix of two voltages on one VCA.


> I was interested in this quad VCA, what do you think about it?
The http://www.doepfer.de/a1324.htm is the exponential counterpart to 
the http://www.doepfer.de/a132.htm (and of course the 132-4 is fourfold, 
while the 132(-1) is twofold).

Florian

> why do we found some VCA's who offer 2 CV Ins if they cannot be used to process EG + Velocity?

I've wondered this too.  In simplified mathematical terms, they're added together like with a mixer, not multiplied together like with another VCA.  Which is all well and good, but it means you can't use it for velocities, you have to use two separate VCAs.  Which is why I'd recommend having an A-132-3 instead of an A-131, given that velocity sensitivity is very expressive and pretty much necessary for making interesting music.

This is a really useful thread, thanks everyone.  All this time, I'd managed to work out the two different ways of wiring up my two VCAs together for velocity sensitivity, but completely overlooked that I should have one of them set to linear mode.  Whoops!  No wonder the CV input of that one had to be so low and its gain so high...  So you've helped me out too with this advice!

All the best,
Zoë.

I must try the Linear / Exponential thing on my after pressure voltage that controls how much vibrato come through. 

David

www.movingisliving.co.uk

Sent from my iPhone 

> On 28 Nov 2016, at 14:39, Zoë Blade zoe@bytenoise.co.uk [Doepfer_a100] <Doepfer_a100@yahoogroups.com> wrote:
> 
> > why do we found some VCA's who offer 2 CV Ins if they cannot be used to process EG + Velocity?
> 
> I've wondered this too. In simplified mathematical terms, they're added together like with a mixer, not multiplied together like with another VCA. Which is all well and good, but it means you can't use it for velocities, you have to use two separate VCAs. Which is why I'd recommend having an A-132-3 instead of an A-131, given that velocity sensitivity is very expressive and pretty much necessary for making interesting music.
> 
> This is a really useful thread, thanks everyone. All this time, I'd managed to work out the two different ways of wiring up my two VCAs together for velocity sensitivity, but completely overlooked that I should have one of them set to linear mode. Whoops! No wonder the CV input of that one had to be so low and its gain so high... So you've helped me out too with this advice!
> 
> All the best,
> Zoë.
> 
>

Hello Florian, 


your focus is magistral, again: thanks ! 


Just few things more. You wrote: 









As written before: our hearing expects exponential changes signal 
levels. So you always need one exponential part in the game. 



And this is assumed now in my comprehension. 

<blockquote>





As you have both, linear voltages (velocity or LFOs) and exponential 
voltages (envelopes), you need both types of VCAs in your system. But I 
tend to have more linear VCAs than exponential ones. 
</blockquote>

Here I have two questions. The first is more about definitions. For each note played by the midi keyboard, the midi interface will provide the system with a fixed voltage (offset) and so the “lin/exp” question is not really meaningful here: there's no evolving data to be sent, just a static value for each note which is neither linear neither exponential. As for the LFO, on the contrary, it is continuously changing and, as far as I can see, it derives more from a (cycled) envelope, which is usually exponential (unless probably the LFO is shaped on a triangle wave). 


The second question is definitely “practical”. 
How better would I combine the parts, this way? 


linear voltage --> exp VCA 

exp voltage --> linear VCA 


Kind regards, 
Diego 




Il giorno 28/nov/2016, alle ore 11:27, Florian Anwander fanwander@mnet-online.de [Doepfer_a100] < Doepfer_a100@yahoogroups.com > ha scritto: 

<blockquote>





Hello Diego 

Am 28.11.2016 um 00:36 schrieb diegora@free.fr [Doepfer_a100]: 
> but the core 
> phrase you wrote missed the essential “verb” 
You are right. Sorry for that 

> «if you mix the velocity voltage with the envelope voltage and feed 
> the sum into one VCA, it will cause the VCA all the time a little bit 
> (according to the velocity voltage) and the evnelope will add on top 
> of this basic level.» 

This should read "...it will cause the VCA to let the signal through all 
the time a little bit...". 

The important thing is, to remember that MIDI-control and 
voltage-control work different: 

The MIDI-system is event orientated. This means: the event Note-On tells 
the note value and the velocity value. It is not the job of the 
MIDI-Keyboard to keep up this information. The receiver has to compute 
and remember the status until the next event is received. 

The CV/Gate-system is status orientated. This means: in a CV-system the 
sender of the information (let it be the keyboard or the MIDI-interface) 
has to deliver continuosly the information about the actual status. The 
receiver does not have to care about it, he can rely that the sender 
provides the status all the time. 

Now back to the velocity topic. 

Lets take an example: 

We switch on the complete system. All voltages, let it be pitch / 
velocity / gate, are 0 Volt. 

From the MIDI-keyboard an noteOn event comes to the MIDI interface. 
This event says: "Note D#1 has been pressed with 50% velocity". 

The MIDI-Interface will translate this to 
* Pitch-voltage = 1.32 Volt (I'm not sure 1.32 is the right value for 
D#1, but it does not matter in this case) 
* Velocity-voltage = 2.5 Volt (assuming the velocity voltages cover 0 to 
5 Volts) 
* Gate-voltage = 5V (assuming gate is 0V/+5V) 

The next event will say: "Note D#1 has been released". 

Now the MIDI-Interface will change only the gate-voltage back to 0 
Volts, but the pitch and velocity voltage will remain: 
* Pitch-voltage = 1,32 Volt 
* Velocity-voltage = 2,5 Volt 
* Gate-voltage = 0V 

Now let us assume, we have used an organ-like envelope at the ADSR (this 
makes it easier to calculate the voltages, because we can simply use the 
gate-voltage as envelope). If we add the envelope-voltage and the 
velocity-voltage, then we would get a voltage of 7.5 Volt at the noteOn 
(2.5V velocity + 5V envelope). At the noteOff event we would get a 
voltage of 2.5 Volt (2.5V velocity + 0V envelope). 

If you feed this to the audio-VCAs control input, then the VCA still 
would send some signal through continuously after the noteOff. 

> Anyway, now I see I always need to adopt 2 VCAs, probably (I try to 
> guess again) the better quality VCA will preferably manage the audio 
> signal (and here I can choose to fire the velocity OR the EG). 
Right. 

> Another subject which probably crosses this application is the 
> difference between linear and exp VCA. Sorry, I won't you to go back 
> to the lin/exp dilemma of the EG segments :-) but if EGs segments are 
> always exp (because it's easier to design), then probably wouldn't be 
> that wise to have an amp which features exp control scales, it might 
> be redundant. It seems that linear VCAs finally are more 
> versatile... 
As written before: our hearing expects exponential changes signal 
levels. So you always need one exponential part in the game. 
As you have both, linear voltages (velocity or LFOs) and exponential 
voltages (envelopes), you need both types of VCAs in your system. But I 
tend to have more linear VCAs than exponential ones. 

> As for the AC-coupled / DC-coupled thing, I really understood very 
> little when I tried to go wiki. 
Basically everything works fine with DC-coupled VCAs, but one might get 
some "whumppp"-sounds at immediate noteOns, if you use a DC-coupled VCA 
with an audiosignal that contains a DC-offset (example: unsymmetric 
pulse wave). 

> One last thing: why do we found some VCA's who offer 2 CV Ins if they 
> cannot be used to process EG + Velocity? Do the 2 inputs affect the 
> amp in the same way or they are wired to different stages? 
Example: if you want to control the overall level of a voice with 
velocity and with an slight amplitude modulation, then you may do that 
with the mix of two voltages on one VCA. 

> I was interested in this quad VCA, what do you think about it? 
The http://www.doepfer.de/a1324.htm is the exponential counterpart to 
the http://www.doepfer.de/a132.htm (and of course the 132-4 is fourfold, 
while the 132(-1) is twofold). 

Florian 

 
</blockquote>