[sdiy] ARP VCO PNP-NPN exponential pair matching

[Pete Swarbrick]

Hi guys
Just to add my recent experience on this very subject, I breadboarded a pair of  Oddy-style VCOs using THAT 340P which worked a treat - no surprises there.
Out of curiosity I substituted a heatsink-gooped BC547/557 pair in one osc and achieved identical performance, at least in the conditions of the hook-up.
THAT340P - £4 each
BC547/557 - £0.10 pair
As Paul says, modern parts are SO much better than the originals available to the designers.

Best 
Pete


PETER SWARBRICK
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-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Dave Leith
Sent: 08 June 2008 05:47
To: Paul Schreiber
Cc: SDIY
Subject: Re: [sdiy] ARP VCO PNP-NPN exponential pair matching

OK, thanks, I have some handy

is there any matching or selection needed?

Dave

On 6/7/08, Paul Schreiber <pschreiber at sbcglobal.net> wrote:
> > The THAT 340P  may work fine for this application but I'm not going to
> > be able to squeeze a 14pin dip package into the space of 2
> > transistors, well at least not with extreme difficulty :-)  so I think
> > I'll prefer to go with discrete transistors if at all possible.
> >
> >
>
>  Then use a BC550/BC560 pair, cheap, high gain, better than ARP ever had :)
>
>  Paul S.
>
>
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