[sdiy] steiner-parker

[Niels A. Moseley]

Hi,

>Hi I found this out and about;
>http://www-timc.imag.fr/Yves.Usson/personnel/SDIY/images/VCF-US1.pdf
>
>What kind of modification would this circuit need to run on less voltage? Is
>it even possible seeing as it's based on transistors?

One thing that comes to mind is that 3k9 resistor at the ground end of the 
differential pair.
This is supposed to be a constant current source. The current will change 
if you only supply -5 V.
This change in current will alter the gain of the differential pair which 
in turn will change the filter's cutoff frequency. It's been a while for me 
since I've analyzed differential pairs so I can't offer the "correct" 
resistor value but there should be plenty info on the web.

Okay, that's my bit ... good luck!

Cheers,
Niels.