Doepfer

Thanks Dieter

That's very interesting

Rgds

David 


David Salter
Senior Consultant
PSG 

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-----Original Message-----
From: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
On Behalf Of hardware@doepfer.de
Sent: 13 November 2006 16:02
To: Doepfer_a100@yahoogroups.com
Subject: AW: [Doepfer_a100] Re: 8 channel cv mixer

> Dieter,
>
> that would be interesting as it would save me daisy chaining mixers 
> and loosing an i/p
>
> david
>
> David Salter
> Senior Consultant
> PSG

David,

the mod is simple:

For the old version of A-138a/b remove the dual opamp IC1 (TL062) of one
of the two modules and connect pin #2 of IC1 (i.e. the inverting input
pin of the first opamp) of both modules. The module with the missing IC1
has no longer a output signal available. If you want to have a output of
this module connect pin #7 of IC1 (i.e. output of the second opamp) of
both modules. Now you have two outputs with adjustable levels available.

For the new version of A-138a/b its similar but here a quad opamp
(TL064) is used. Remove the quad opamp IC1 (TL064) of one of the two
modules and connect pin #9 of IC1 (i.e. the inverting input pin of the
first opamp) of both modules. The module with the missing IC1 has no
longer a output signal available. If you want to have a output connect
the output sockets of both modules. In this case the output of the
second module cannot be adjusted (different circuit compared to the old
version). But you may connect the pin header JP2 of the first module to
the output of the second module. Then you have the inverted output
available.

For the polarizing mixer A-138c remove IC3 (TL062) of one of the two
modules and connect pin #6 of IC3 (i.e. the inverting input pin of the
mixing opamp) of both modules. The module with the missing IC3 has no
longer a output signal available. If you want to have a output of this
module connect pin #1 of IC3 (i.e. output of the final opamp) of both
modules. In this case the level is the same for both outputs. The master
control of the second module has no function.

We already discussed a simple "mixing expander" module that could be
used to add 5 more inputs to A-138a/b. It will be about 20-30% cheaper
than an A-138a/b as no integrated circuits and no power supply are
necessary for such a simple module (only a front panel with five
sockets, five
potentiometers+knobs and five resistors). How about a poll ?

Good luck,
Dieter Doepfer



 
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