Cut/Boost of Shelving Filter
« on: December 12, 2018, 01:07:38 PM »
Hello everybody

This circuit is a high shelfing-Filter. I do have trouble calculating the maximum cut / boost. I know that the devider (R3 and R4) sets the maximum cut and boost but how do I calculate it exactly, with the given resistor values? Thanks for your help!


moamps

Re: Cut/Boost of Shelving Filter
« Reply #1 on: December 13, 2018, 04:13:08 PM »
max boost=max cut=20log ((1-2R4/(R3+R4))=16.8dB
You will get more attention if you post it to Drawing Board.

Re: Cut/Boost of Shelving Filter
« Reply #2 on: December 13, 2018, 05:15:14 PM »
Thank you very much for your help! I really appreciate it!

Re: Cut/Boost of Shelving Filter
« Reply #3 on: December 14, 2018, 04:44:28 AM »
@moapms:

With this equation, I get the max. cut of -16.8dB. I know that the max. Boost is the same, with +16dB. But the equation for the max. boost must be slightly different?! Do you know this equation as well?

moamps

Re: Cut/Boost of Shelving Filter
« Reply #4 on: December 14, 2018, 07:02:34 AM »
Here you go:

Re: Cut/Boost of Shelving Filter
« Reply #5 on: December 14, 2018, 04:33:54 PM »
Thank you very much!!

abbey road d enfer

Re: Cut/Boost of Shelving Filter
« Reply #6 on: December 16, 2018, 10:01:51 AM »
Hello everybody

This circuit is a high shelfing-Filter. I do have trouble calculating the maximum cut / boost. I know that the devider (R3 and R4) sets the maximum cut and boost but how do I calculate it exactly, with the given resistor values? Thanks for your help!
Note that, according to the mathematical analysis, the max boost/cut will never be achieved because it is an asymptotic response, that can be reached only at a virtual infinite frequency. In reality, the finite gain of the opamps will define the actual response.
I would suggest you simulate the circuit in LTspice (a free software by Linear Technology), so you will see practical results and how components interact with the actual response.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

Related Topics

  Subject / Started by Replies Last post
26 Replies
17406 Views
Last post September 17, 2004, 05:33:53 PM
by NewYorkDave
4 Replies
2406 Views
Last post November 03, 2004, 04:23:06 PM
by Joechris
2 Replies
1666 Views
Last post December 09, 2005, 01:02:41 PM
by extraware
7 Replies
1810 Views
Last post May 04, 2010, 09:27:11 PM
by PRR