Hi Thomas,

I just changed the LM324 for the TL074 (very cheap €0,30) in A-131 and a138b.
Cannot compare A/B, but I also think that it handles higher inputs better.
Do you think the LME49740 (around €8) will be another improvement Is the
pin-layout the same So just swap it

Thanks
Dirk


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Am 03.07.2012 um 13:55 schrieb thomas_escure < thomas_escure@... >:



Hi Dmitry,

I also am very interested about the possibility of replacing ICs to increase
the audio quality of my beloved Doepfer modules.

For example, I used to have problems with my A-131s : the noisefloor was a
little too high for my tastes and when I tried to increase the input level I
wasn't pleased by the distortion.

Then a very kind fellow on Muffwiggler's forum suggested that I replace the
LM324 IC (responsible for audio duties) by an LME49740. The difference, to my
ears, was astonishing ! So I did this very simple mod on my three A-131s and
now I love the A-131, it has become my favorite VCA (and I tried about 6 from
different makers).

It must be noted that the IC swap does not really lower the noisefloor, but it
handles higher input levels much better (in my opinion) so that noise becomes
inaudible. Also when I really push it into distortion I like the caracter of
the sound.

I do not own an A-138 for the moment but I will sure try this AD OP470 IC when
I get one.

Please let me know if you can find other good sounding ICs for Doepfer modules
!

Dieter, if you're reading this please be sure that I greatly respect your
work.
I understand that compromises have to be made when running a product line,
that I think is well appreciated by a lot of customers.

Best regards,

Thomas

--- In Doepfer_a100@yahoogroups.com , "therpocc" <dmitry.shtatnov@...> wrote:
>
> Dear Dieter, i'm glad to hear about your interest.
> Concerning the price: you pricelist includes different rack cases having
different cost, items such as Hi-End VCO, blue-LED versions of modules and
other items. Offering high-fidelity might be just another option. (Finally it
can be just another OEM items such as CEM chips, LEDs, sockets etc)
> I'm not a professional engineer, but you are. So, i believe you can find
some more cost-effective components with quality close to this particular
Analog Devices component but higher then just plain TL064...
> Anyway, thanks for your interest.
> Best regards,
> Dmitry
>
> --- In Doepfer_a100@yahoogroups.com , <yahoo@> wrote:
> >
> > Dmitry,
> >
> > thank you for the detailed report. That was interesting for me too.
> > Unfortunately the OP470 is very expensive (~ Euro 15 here in Germany) and
> > would increase the price of the modules clearly.
> >
> > Best wishes
> > Dieter Doepfer
>



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