how could I scoop a specific frequency?

[Derringer]

I've got a fuzz build and I want to scoop out 1.5kH ... but I want to leave the frequencies above and below that

I arrived at the frequency by playing with a post active-EQ



Thanks for any tips

[frank_p]

Search for an active band-pass (BP) filter.  There is an example in Microelectronic circuits book chapter 11.6 : second order active filter without inductors.  You will need one or two dual opamps for that. 

[frequencycentral]

Search for an active band-pass (BP) filter.  There is an example in Microelectronic circuits book chapter 11.6 : second order active filter without inductors.  You will need one or two dual opamps for that. 

Wouldn't it actually be a 'notch reject' filter - not a band pass filter? The poster wants to reject the frequency not accentuate it.

http://en.wikipedia.org/wiki/Notch_filter

[alanlan]

Search for an active band-pass (BP) filter.  There is an example in Microelectronic circuits book chapter 11.6 : second order active filter without inductors.  You will need one or two dual opamps for that. 

Wouldn't it actually be a 'notch reject' filter - not a band pass filter? The poster wants to reject the frequency not accentuate it.

http://en.wikipedia.org/wiki/Notch_filter

Bandpass filters usually have cut and boost capability so it can do both.

You could also consider a passive LCR notch filter.

[R.G.]

Twin-T, either passive or active, or Bridged-T. Much simpler than LC and easier to tune to a specific Q.

You'll find that the issue is not can you remove one frequency, but whether you can remove a specific one, and how much of the frequencies near it on either side that you lose as well.

[B Tremblay]

Check out this thread:
http://www.diystompboxes.com/smfforum/index.php?topic=25788.0

[frank_p]

Sorry I red too fast...   

[Derringer]

Check out this thread:
http://www.diystompboxes.com/smfforum/index.php?topic=25788.0

good thread ... thanks

I didn't know that circuit had a name (T-Notch) but that's what I've actually been working with so far .... I had taken it from the Superfuzz design


but that info for finding the right frequency is just what I was looking for

thanks for the replies all!

[frank_p]

I remember R.G. talked about a book called Active Filters Cookbooks:

http://www.diystompboxes.com/smfforum/index.php?topic=67249.msg535641#msg535641

If I remember well it is about 40$.  I would like to buy it but I still have to do some homeworks since I bought a bunch of electronics books lately (including R.G.'s one about layouts).

Stopping buying equipment and buying book is good, but you still have to read them (a couple of time so everything get glued in your mind) : it's like having tons of guitars and playing only one of them. 

Have fun !