hello zoran,

i mostly use 2 old a131, but i also have two newer a131 and
i don't have that problem you mentioned. the newer a131 are a bit
more noisy, but they do not distort the signal like you described,
it is just a bit of hum and you can barely notice it.
i believe you, don't get me wrong. i just don't understand
how different our modules can be. maybe i'm too much
on the lofi side these days ;-)

i also have a blacet vca and i like it very much, but you have to
notice that the blacet needs a voltage of +10v to open completely,
which is not common with doepfer modules.

best wishes

ingo



--- In Doepfer_a100@yahoogroups.com, "Zoran Bosnjak" <dj_allin@h...>
wrote:

> Hi, thanks for the post. Unfortunatelly, I don't have any old A-131

VCAs!

> Both units I had problems with are 2 to 7 months old. Please don't

get me

> wrong, but what I am experiencing on both of these A-131s is not

occasional

> distortion at the loudest points, but pitched hum that follows the

melody. I

> have samples to illustrate this for both VCAs I owned (returning

second one

> today, first one was returned already).
> So what is my solution than First, I tested all three available

VCAs (A131,

> A132, A109) last night little bit more, to confirm results. And

here it is:

> - A-131 - cannot use it (pitched hum)
> - A-109 - barely noticable distortion on loudest notes in bass line

(your

> "normal" distortion) - I am keeping this module, because VCA on it

can do

> the task, and filter is very good
>
> So you might be asking: look at this guy! He says both A-131 and A-

109 are

> at least imperfect but he still takes one anyway. And this is my

point

> exactly: imperfection between two is very different in character

and

> loudness (I am looking for the right word - while you really have

to try

> hard to notice distortion on A109, on A131 it is more like a second

voice

> :-).
>
> - I also checked A-132 - no noise whatsoever. But dynamics (volume

changes)

> were slightly different than what I am used to (I guess because it

is linear

> VCA).
>
> So, my choice is A-109 for audio. What would have happened if A-109

was not

> good enough I would play more with A-132, and if they were not
> satisfactory, I could always use them for CV duties. And than I

would have

> ordered Blacet VCA and see where that takes me.
>
> Regards
>
> Zoran
>
>
> >From: Florian Anwander <Florian.Anwander@c...>
> >Reply-To: Doepfer_a100@yahoogroups.com
> >To: Doepfer_a100@yahoogroups.com
> >Subject: Re: 1 Noisy A-131 VCA
> >Date: Wed, 04 Feb 2004 11:29:05 +0100
> >
> >Hi Zoran
> >
> >The reason for the noise is quite simple to explain. The old A-

130/131

> >used Curtis CEM-VCA-Chips (which is out of production as far as I

know),

> >which had low noise. The new 130/131 uses CA3080 OTAs (like the 132
> >always did). To my knowledge there is no difference between the

Audio

> >circuit of the new 130 and the 132. The new 131 is noisier,

because its

> >logarithmic behaviour requires a higher amplification. More
> >amplification -> more noise.
> >
> > > This noise disappears when using A-109 VCA.
> >This is clear, because the A-109 uses again another Curtis CEM-

Chip (but

> >a different from the one in the old A131).
> >
> >If you have an old 131, you should think about an extension as it

is

> >mentioned in the service manual of the module. The CEM VCA-chip in

the

> >A131 contains two(!) VCAs but only one is used. The pcb of the A-

131

> >offers the possiblity to access the second VCA, you need a second

A-131

> >pcb and frontplate, but without the second CEM-chip.
> >
> >It should be possible also to implement this as a quite simple diy

project.

> >
> >
> >Florian
> >--
> >Florian Anwander |ConSol
> >Tel. +49(89)45841-133 |Consulting&Solutions Software

GmbH

> >Fax +49(89)45841-111 |Franziskanerstr. 38, D-81669

München

> >email: florian.anwander@c... |http://www.consol.de
> >
>
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