High pass active filter questions

[Heemis]

So I've been looking for a way to set up a variable frequency active high pass filter.  If someone can confirm this, I would be eternally grateful.  I'm looking at this schem from the National Semiconductor op amp notes:



As per my thinking, if I switch the 110K resistors to a 100K dual gang pot, with 20K series resistors with each, that will give me variable resistance from 20K to 120K, which should result in a sweepable frequency from about 88 Hz to 530 Hz.  Am I correct in this assumption?

[alanlan]

Don't see why not although I haven't checked the actual frequencies

[chi_boy]

This conversation was along those lines.  You may be able to glean some information here:

http://www.diystompboxes.com/smfforum/index.php?topic=72601.0

[Sacorus]

Old topic here, but quick question.

When using a filter like this;


When using a single 9V supply(V- on op amp grounded), should the ground on the the filter be tied to Vbias instead of ground?

[ashcat_lt]

It absolutely must be.

[Sacorus]

Cheers, good to clarify before i build