[sdiy] State Variable Filter in AudioXpress

[David Brown]

There's a 14 page article in this month's AudioXpress on a State 
Variable Filter design by Dennis Colin, designer of the original ARP 
1047 filter.  This design is for a stand alone filter for speaker 
testing.  I thought his temperature compensation was interesting.  He 
used a diode and two regulators to compensate the control voltages 
and includes data on the stability.  Full schematics for a 20 - 20 
KHz filter with adjustable Q of 0.5 to 100.  Nicely written.

Dave