3db-12db drop/octave variable filters?

[Earthscum]

I was wondering if there is any way to make a variable 3-12 db filter. I want something that will have a nice even dropoff.

Most of the variable filters I've tried seem to have some sort of shelving effect to them. Is this maybe sorted out by altering values for more or less circuit impedance? I don't have an o-scope yet, so it's hard for me to tell what's getting dropped smoothly or not.

Thanks.

[Mark Hammer]

Do you mean something that can be continuously varied between 3 and 12db slope, or do you mean anything with a slope somewhere in that range, whose corner frequency can be varied?

[PRR]

> I don't have an o-scope yet, so it's hard for me to tell what's getting dropped smoothly

That's not even a good job for a 'scope.

You want a variable sine signal-generator and a good AC/Audio voltmeter.

An R-C or C-R filter will give a low-pass or high-pass at 6dB/octave to "infinity". If you are getting a shelf, you have a R-C-R filter; many boosts are this way.

Variable 3dB/octave is difficult and so gentle that it probably isn't what you want.

Variable 12dB/oct is a standard circuit, examples all over the interweb. In addition to frequency, you may specify a Q or Damping to give a bump-up before the roll-off.