Page 1 of 1

1 - 2 pole switchable filter

PostPosted: 15 Nov 2017, 02:24
by Optical
Hi all
I'm looking to build an adjustable filter that is switchable slope between 1 and 2 poles. Minimising part count and complexity without sacrificing tone are the objectives. Both high and low pass filters are needed.

Options I'm looking at are:
1. Sallen-key for the 2 pole and RC for the 1 pole, switch selects between output of either. The highest part count and complexity but best tone(?)
2. RC filter in series with another RC filter. Switch selects between output of first or second filter. Easy but I'm not sure not sure how good a series RC filters sound?
3. Some way to use a switch to change a Sallan-key filter into a single pole. Might be possible by disconnecting the feedback cap on a low pass filter although the series resistors would change the corner frequency. Not sure about how it would be done on a high pass filter...

Any opinions?

Re: 1 - 2 pole switchable filter

PostPosted: 15 Nov 2017, 13:06
by phatt
You can always find cal online stuff to get an idea,, one here (http://sim.okawa-denshi.jp/en/OPseikiLowkeisan.htm)
But I would simply breadboard the circuits and test all options. Although it sounds like a lot of work and takes a long time,,,,,,,,,,
IMExperience I've found that is the shortest path to success. :secret:
I use a sim and bread board and my ears to fine tune the outcome. :thumbsup
Phil.