madbeanpedals::forum

Projects => General Questions => Topic started by: LaceSensor on September 24, 2025, 06:42:11 AM

Title: Adjust LP and HP filters
Post by: LaceSensor on September 24, 2025, 06:42:11 AM
Had a request to adjust the sweep range of this project .
https://docs.pedalpcb.com/project/FrequencyInterchange-PedalPCB.pdf

Does anyone have a good calculator for the type of LPF and HPF here? Im comfortable with one-potentiometer LP circuits, but these are dual-gang and I am not sure how to adjust the capacitors/resistors to effect the change.

The desired range is LP - 1k to 6k HP 30-250hz

Thanks for your help

Ian
Title: Re: Adjust LP and HP filters
Post by: LaceSensor on September 25, 2025, 10:03:12 AM
Ive been reading some documents on second order filters and I cant even get the example maths they provide to work with their "default" circuits.

eg https://k7mem.com/Fil_2nd_Active_LP_HP.html
eg https://www.electronics-tutorials.ws/filter/filter_6.html

Any help would be super appreciated!

Cheers
Title: Re: Adjust LP and HP filters
Post by: mauman on September 26, 2025, 01:04:23 AM
You could try a sim in Spice and experimentally tweak the components around the LP and HP pots, there aren't that many. 
Title: Re: Adjust LP and HP filters
Post by: NorthCoast on September 26, 2025, 02:42:11 AM
How about this:

https://www.allaboutcircuits.com/video-tutorials/op-amps-low-pass-and-high-pass-active-filters/

http://sim.okawa-denshi.jp/en/OPseikiLowkeisan.htm
http://sim.okawa-denshi.jp/en/OPseikiHikeisan.htm
Title: Re: Adjust LP and HP filters
Post by: LaceSensor on September 26, 2025, 01:31:58 PM
Quote from: NorthCoast on September 26, 2025, 02:42:11 AMHow about this:

https://www.allaboutcircuits.com/video-tutorials/op-amps-low-pass-and-high-pass-active-filters/

http://sim.okawa-denshi.jp/en/OPseikiLowkeisan.htm
http://sim.okawa-denshi.jp/en/OPseikiHikeisan.htm
Dude! Legendary. This works/worked perfectly to simulate the original circuit.
Im working on adjusting values now. Cheers