Doepfer

I've just got my first eurorack modular which I've been using for the
first time today and have a question regarding the A-132-3 VCA. I
bought two of these as they seem to offer the most flexibility in a
small system, but when I patch the VCO directly into the VCA and
control the amplitude with an A-140 ADSR, even with the gain control
set to zero, there is a constant bleed-through of the note.

To be honest, I don't completely understand the function of the gain
control, as I'd have assumed that when set to zero no sound would pass
through the VCA, and there appeaar to be no manual pages for it. Can
anyone help?

Thanks,
Matt

Hi Matt,

You are right in assuming that a VCA shouldn't pass any
signal when the gain is completely closed.

A "Gain control", or "Initial Gain" as it's mostly labeled, 
is actually nothing more than a variable (through the pot)
DC voltage added to the CV inputs. For instance, if you'd
close the Gain pot, and then add a steady DC signal 
(say +8V) to the CV input, you'd achieve the same effect.

Unfortunately "Gain" or "Initial Gain" isn't entirely correct
as a label -- though it's been in use since ehm, forever -- 
because it doesn't add any gain in most VCA's.
In the case of the 132-2 however, it is possible to have
more than "unity gain" (1 to 1), which can possibly lead
to clipping...

Most VCA's have trimmers on the PCB to trim back the
"CV rejection" and "signal bleedthrough" (*). This should
be set properly in the factory. If that's not the case, then
I guess the module should be re-trimmed at the factory.

(*) I don't know if the 132-3 has preset trimmers.


If you're 'opening' the VCA with a ADSR, make sure that
the Sustain is completely closed and the gate is OFF.
Otherwise you're sending a DC voltage to the VCA, 
which could account for the so-called bleedthrough.


_g

On 19 Jan 2011, at 13:24, Matt wrote:

> I've just got my first eurorack modular which I've been using for the
> first time today and have a question regarding the A-132-3 VCA. I
> bought two of these as they seem to offer the most flexibility in a
> small system, but when I patch the VCO directly into the VCA and
> control the amplitude with an A-140 ADSR, even with the gain control
> set to zero, there is a constant bleed-through of the note.
> 
> To be honest, I don't completely understand the function of the gain
> control, as I'd have assumed that when set to zero no sound would pass
> through the VCA, and there appeaar to be no manual pages for it. Can
> anyone help?
> 
> Thanks,
> Matt

> I've just got my first eurorack modular which I've been using for the
> first time today and have a question regarding the A-132-3 VCA. I
> bought two of these as they seem to offer the most flexibility in a
> small system, but when I patch the VCO directly into the VCA and
> control the amplitude with an A-140 ADSR, even with the gain control
> set to zero, there is a constant bleed-through of the note.
>
> To be honest, I don't completely understand the function of the gain
> control, as I'd have assumed that when set to zero no sound would pass
> through the VCA, and there appeaar to be no manual pages for it. Can
> anyone help?
>
> Thanks,
> Matt

In the linear mode the VCA should let pass no signal if the Gain control is
set to zero and no CV external CV signal is applied (or the CV attenuator is
set to zero). In the exponential mode the situation is different. Please
refer to my message/answer from January 10th 2011 concerning the lin/exp
mode of the A-132-3.

Best wishes
Dieter Doepfer

Dear Dieter,

Both of the A-132-3 modules I have (purchased new very recently) pass continuous low level audio signal even when the Gain control is set to zero, the module is switched to Linear, and no  external CV signal is applied (although the signal level varies with each VCA). Is there an internal adjustment I could make to fix this? 

With thanks for your help.
Matt

>In the linear mode the VCA should let pass no signal if the Gain >control is set to zero and no external CV signal is applied (or the >CV attenuator is set to zero). In the exponential mode the situation >is different. Please refer to my message/answer from January 10th 2011 >concerning the lin/exp mode of the A-132-3.
> 
> Best wishes
> Dieter Doepfer
>

> Dear Dieter,
>
> Both of the A-132-3 modules I have (purchased new very recently)
> pass continuous low level audio signal even when the Gain control
> is set to zero, the module is switched to Linear, and no
> external CV signal is applied (although the signal level varies
> with each VCA). Is there an internal adjustment I could make to fix this?
>
> With thanks for your help.
> Matt

There is no internal adjustment but it's possible to connect the CV summing
node via a high value resistor (MOhm range) to -12V. This offsets the bias a
bit to the negative and the VCA will close. For details I need to know if
you own the old version with CEM3360 or the new one with SSM2164 ?

Best wishes
Dieter Doepfer

Dear Dieter,

Both of the A-132-3 modules I have contain the SSM2164. If a modification is possible that would be great, but I would need clear layman's instructions as my understanding of electronics is minimal, although I can solder adequately.

So is it normal for the A-132-3 to continually pass low-level audio (as I wrote, the amount varies from each VCA)?

Thanks again for your help with this.

Best wishes,
Matt


--- In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote:

>
> > Dear Dieter,
> >
> > Both of the A-132-3 modules I have (purchased new very recently)
> > pass continuous low level audio signal even when the Gain control
> > is set to zero, the module is switched to Linear, and no
> > external CV signal is applied (although the signal level varies
> > with each VCA). Is there an internal adjustment I could make to fix this?
> >
> > With thanks for your help.
> > Matt
> 
> There is no internal adjustment but it's possible to connect the CV > summing node via a high value resistor (MOhm range) to -12V. This offsets the bias a
> bit to the negative and the VCA will close. For details I need to know if
> you own the old version with CEM3360 or the new one with SSM2164 ?
> 
> Best wishes
> Dieter Doepfer
>

Hi Giorgio,

I bought the P9 suitcase new from Thomann about two weeks ago.

Matt

--- In Doepfer_a100@yahoogroups.com, dancemachine <dancemachine@...> wrote:

>
> my 132-2 does not do this.  sounds like you might have something wrong with
> your system.  did you get them new?  if so maybe something with your power
> supply is off.  or used?  if so, ask whoever you got them from.  I will
> check mine again and see if I can pop it out and figure out which version it
> is as well.
> 
> good luck
> 
> -giorgio
> 
> On Wed, Jan 19, 2011 at 7:24 AM, Matt <matt.fretton@...> wrote:
> 
> >
> >
> > I've just got my first eurorack modular which I've been using for the
> > first time today and have a question regarding the A-132-3 VCA. I
> > bought two of these as they seem to offer the most flexibility in a
> > small system, but when I patch the VCO directly into the VCA and
> > control the amplitude with an A-140 ADSR, even with the gain control
> > set to zero, there is a constant bleed-through of the note.
> >
> > To be honest, I don't completely understand the function of the gain
> > control, as I'd have assumed that when set to zero no sound would pass
> > through the VCA, and there appeaar to be no manual pages for it. Can
> > anyone help?
> >
> > Thanks,
> > Matt
> >  
> >
> 
> 
> [Non-text portions of this message have been removed]
>

my 132-2 does not do this.  sounds like you might have something wrong with
your system.  did you get them new?  if so maybe something with your power
supply is off.  or used?  if so, ask whoever you got them from.  I will
check mine again and see if I can pop it out and figure out which version it
is as well.

good luck

-giorgio

On Wed, Jan 19, 2011 at 7:24 AM, Matt <matt.fretton@gmail.com> wrote:

>
>
> I've just got my first eurorack modular which I've been using for the
> first time today and have a question regarding the A-132-3 VCA. I
> bought two of these as they seem to offer the most flexibility in a
> small system, but when I patch the VCO directly into the VCA and
> control the amplitude with an A-140 ADSR, even with the gain control
> set to zero, there is a constant bleed-through of the note.
>
> To be honest, I don't completely understand the function of the gain
> control, as I'd have assumed that when set to zero no sound would pass
> through the VCA, and there appeaar to be no manual pages for it. Can
> anyone help?
>
> Thanks,
> Matt
>  
>


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

with the modules?  you might want to talk to them about this.  unless maybe
you are just getting a tiny bit of bleed through and somehow your gain
staging is goofed up.  that's the only other thing I could thing of besides
faulty gear.

On Thu, Jan 20, 2011 at 12:00 PM, mfretton <matt.fretton@gmail.com> wrote:

>
>
> Hi Giorgio,
>
> I bought the P9 suitcase new from Thomann about two weeks ago.
>
> Matt
>
>
> --- In Doepfer_a100@yahoogroups.com <Doepfer_a100%40yahoogroups.com>,
> dancemachine <dancemachine@...> wrote:
> >
> > my 132-2 does not do this. sounds like you might have something wrong
> with
> > your system. did you get them new? if so maybe something with your power
> > supply is off. or used? if so, ask whoever you got them from. I will
> > check mine again and see if I can pop it out and figure out which version
> it
> > is as well.
> >
> > good luck
> >
> > -giorgio
> >
> > On Wed, Jan 19, 2011 at 7:24 AM, Matt <matt.fretton@...> wrote:
> >
> > >
> > >
> > > I've just got my first eurorack modular which I've been using for the
> > > first time today and have a question regarding the A-132-3 VCA. I
> > > bought two of these as they seem to offer the most flexibility in a
> > > small system, but when I patch the VCO directly into the VCA and
> > > control the amplitude with an A-140 ADSR, even with the gain control
> > > set to zero, there is a constant bleed-through of the note.
> > >
> > > To be honest, I don't completely understand the function of the gain
> > > control, as I'd have assumed that when set to zero no sound would pass
> > > through the VCA, and there appeaar to be no manual pages for it. Can
> > > anyone help?
> > >
> > > Thanks,
> > > Matt
> > >
> > >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>  
>


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

Yes, I bought the ccase and modules at the same time. I'll wait to see what Dieter suggests in response to my reply to him but, as I'm new to modular, I'm concerned to ascertain if I'm doing something wrong, if the modules are faulty, or if it's in the nature of the module to bleed audio in this way (which it seems is not the case). Matt

--- In Doepfer_a100@yahoogroups.com, dancemachine <dancemachine@...> wrote:

>
> with the modules?  you might want to talk to them about this.  unless maybe
> you are just getting a tiny bit of bleed through and somehow your gain
> staging is goofed up.  that's the only other thing I could thing of besides
> faulty gear.
> 
> On Thu, Jan 20, 2011 at 12:00 PM, mfretton <matt.fretton@...> wrote:
> 
> >
> >
> > Hi Giorgio,
> >
> > I bought the P9 suitcase new from Thomann about two weeks ago.
> >
> > Matt
> >
> >
> > --- In Doepfer_a100@yahoogroups.com <Doepfer_a100%40yahoogroups.com>,
> > dancemachine <dancemachine@> wrote:
> > >
> > > my 132-2 does not do this. sounds like you might have something wrong
> > with
> > > your system. did you get them new? if so maybe something with your power
> > > supply is off. or used? if so, ask whoever you got them from. I will
> > > check mine again and see if I can pop it out and figure out which version
> > it
> > > is as well.
> > >
> > > good luck
> > >
> > > -giorgio
> > >
> > > On Wed, Jan 19, 2011 at 7:24 AM, Matt <matt.fretton@> wrote:
> > >
> > > >
> > > >
> > > > I've just got my first eurorack modular which I've been using for the
> > > > first time today and have a question regarding the A-132-3 VCA. I
> > > > bought two of these as they seem to offer the most flexibility in a
> > > > small system, but when I patch the VCO directly into the VCA and
> > > > control the amplitude with an A-140 ADSR, even with the gain control
> > > > set to zero, there is a constant bleed-through of the note.
> > > >
> > > > To be honest, I don't completely understand the function of the gain
> > > > control, as I'd have assumed that when set to zero no sound would pass
> > > > through the VCA, and there appeaar to be no manual pages for it. Can
> > > > anyone help?
> > > >
> > > > Thanks,
> > > > Matt
> > > >
> > > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> >  
> >
> 
> 
> [Non-text portions of this message have been removed]
>

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von mfretton
> Gesendet: Donnerstag, 20. Januar 2011 12:36
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Re: A-132-3 question
>
>
> Dear Dieter,
>
> Both of the A-132-3 modules I have contain the SSM2164. If a
> modification is possible that would be great, but I would need
> clear layman's instructions as my understanding of electronics is
> minimal, although I can solder adequately.
>
> So is it normal for the A-132-3 to continually pass low-level
> audio (as I wrote, the amount varies from each VCA)?
>
> Thanks again for your help with this.
>
> Best wishes,
> Matt

To add a small negative CV offset one has to solder a resistor with about
4M7...10M between pin 13 of IC2 (the upper TL072) and -12V for the upper
unit. And another resistor between pin 9 of IC3 (the lower TL072) and -12V
for the lower unit. These pins are the summing nodes for the control
voltages. With this modification the VCA should fully close in the linear
mode.

Please let me know if other user have similar problems. In this case I will
instruct our production company to add these resistors

Best wishes
Dieter Doepfer

Dear Dieter,

Thanks for your reply but, unfortunately, this is beyond my ability, so can I send the modules back to you for modification?

Thanks,
Matt

--- In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote:

>
> 
> To add a small negative CV offset one has to solder a resistor with about
> 4M7...10M between pin 13 of IC2 (the upper TL072) and -12V for the upper
> unit. And another resistor between pin 9 of IC3 (the lower TL072) and -12V
> for the lower unit. These pins are the summing nodes for the control
> voltages. With this modification the VCA should fully close in the linear
> mode.
> 
> Please let me know if other user have similar problems. In this case I will
> instruct our production company to add these resistors
> 
> Best wishes
> Dieter Doepfer
>

> Dear Dieter,
>
> Thanks for your reply but, unfortunately, this is beyond my
> ability, so can I send the modules back to you for modification?
>
> Thanks,
> Matt

It depends upon your home country. Shipments from outside the EU may cause a
lot of troubles. It happened already that we had to pick up such goods about
40 km away from the corresponding customs facilities and fill a lot of forms
for importation (causing charges far beyond the price of the module). If you
are within the EU it's no problem.


Best wishes
Dieter Doepfer