Doepfer

Rack space is an issue atm and i need both lin and log vcas, so im
looking at a little shopping. Since the quad vca was put back to
summer ive started to look at the A-132-1 was wondering if it was
possible to modify it?

regards

Paul

> Rack space is an issue atm and i need both lin and log vcas, so im
> looking at a little shopping. Since the quad vca was put back to
> summer ive started to look at the A-132-1 was wondering if it was
> possible to modify it?
>
> regards
>
> Paul

Depends upon the perception of "modify". You have to replace the linear
current source of the A-132-1 by an exponential type (one operational
amplifier, two transistors and a couple of resistors and capacitors). In any
case electronic experience is necessary. Or you look at the A-132-3 which
has two VCAs that can be switched to linear or exponential.

Best wishes
Dieter Doepfer

Thanks for the reply, yes i did look at the 132-3 but i simplt dont have the
rack space, i need to add 4 vcas. Changing the parts is no problem (i do
this all day at work) Are you able to let me know a parts list and which
need to be changed.

Paul

On Tue, Feb 9, 2010 at 6:21 PM, <yahoo@doepfer.de> wrote:

>
>
> > Rack space is an issue atm and i need both lin and log vcas, so im
> > looking at a little shopping. Since the quad vca was put back to
> > summer ive started to look at the A-132-1 was wondering if it was
> > possible to modify it?
> >
> > regards
> >
> > Paul
>
> Depends upon the perception of "modify". You have to replace the linear
> current source of the A-132-1 by an exponential type (one operational
> amplifier, two transistors and a couple of resistors and capacitors). In
> any
> case electronic experience is necessary. Or you look at the A-132-3 which
> has two VCAs that can be switched to linear or exponential.
>
> Best wishes
> Dieter Doepfer
>
>  
>


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

> Thanks for the reply, yes i did look at the 132-3 but i simplt dont have
the
> rack space, i need to add 4 vcas. Changing the parts is no problem (i do
> this all day at work) Are you able to let me know a parts list and which
> need to be changed.
>
> Paul

You do not simply have to change parts but to built a exponential current
source which you can find in an electronic schoolbook (e.g. Tietze/Schenk
Halbleiter Schaltungstechnik in Germany, but I'm sure there are many English
books available too). Sorry - I don't have the time to write a detailed
explanation how to do this as it's not that easy. In any case you have to be
experienced with electronics. The exponential current source circuit is used
in most of the CA3080 based filters and exponential VCAs and you will find
it in the internet (e.g. http://www.musiksynthesizer.de/?p=84). You may even
use the exponential current source of the VCF in the Oberheim SEM module
which can be found also in the internet.
If you search e.g. for "exponential current source" or "exponential
voltage-to-current converter" in Google or Wikipedia it should be no problem
to find the circuit.

Best wishes
Dieter Doepfer

thanks for the tips, itll give me something to get my teeth into :-)

Paul

On Wed, Feb 10, 2010 at 10:24 AM, <yahoo@doepfer.de> wrote:

>
>
> > Thanks for the reply, yes i did look at the 132-3 but i simplt dont have
> the
> > rack space, i need to add 4 vcas. Changing the parts is no problem (i do
> > this all day at work) Are you able to let me know a parts list and which
> > need to be changed.
> >
> > Paul
>
> You do not simply have to change parts but to built a exponential current
> source which you can find in an electronic schoolbook (e.g. Tietze/Schenk
> Halbleiter Schaltungstechnik in Germany, but I'm sure there are many
> English
> books available too). Sorry - I don't have the time to write a detailed
> explanation how to do this as it's not that easy. In any case you have to
> be
> experienced with electronics. The exponential current source circuit is
> used
> in most of the CA3080 based filters and exponential VCAs and you will find
> it in the internet (e.g. http://www.musiksynthesizer.de/?p=84). You may
> even
> use the exponential current source of the VCF in the Oberheim SEM module
> which can be found also in the internet.
> If you search e.g. for "exponential current source" or "exponential
> voltage-to-current converter" in Google or Wikipedia it should be no
> problem
> to find the circuit.
>
> Best wishes
> Dieter Doepfer
>
>  
>


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