[sdiy] Home made OTA !

[Roman]

those are common discrete transistors (not pairs). Their TH equivalents
are BC550 and BC560, or any other NPN and PNP respectively.
The VCA core is taken from SSM2040 cell, or was it 2044?
It works good, but with very small signal. AFAIR more than 30mVpp
at the base gives considerable asymetric distortion.
BTW, I'd use the dual versions now, that is with the 'S' suffix. That
VCA would be much smaller then, not to mention better thermal
behaviour.

Roman

----- Original Message -----
From: "Roy J. Tellason" <rtellason at blazenet.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, June 16, 2005 5:09 PM
Subject: Re: [sdiy] Home made OTA !


> On Thursday 16 June 2005 09:21 am, Yves Usson wrote:
> > Hi Fredrik
> >
> > I suggest that you have a look to the discrte VCA developped
> > by Roman Sowa who actually did all that some years ago. It will save you
> > times.
> > http://www.sowa.synth.net/modular/m_xvca.gif
> >
> > He uses very similar SMD transistors.
> >
> > Cheers
> >
> > Yves
>
> Interesting circuit,  but as for SMD I'm not going there.  Is this do-able
> with thru-hole parts?  Anybody care to recommend some other transistor
> numbers?
>