bass boost filter circuit

[Frances Rhodes]

hi everyone

i have been trying to find information about bass booster circuits and stumbled upon baxandall circuits quite a few times but didn't really find the information i was looking for.
after quite some time i thought of 3 options
- modify a baxandall circuit to have only a bass frequencies lift with well chosen values to have an effect only on needed frequencies
- modify a multiband EQ to only boost the needed frequency range
- use a sallen-key style high pass filter with a fairly low fixed cutoff frequency and change the resonance with a pot

i know the baxandall circuit isn't a bad idea since it is used in many effects such as Xotic AC/RC boosters, but maybe there is a better (easier, more musical, nicer-to-the-ear...) way of doing it.
if anyone has a suggestion, i'd be happy to talk about this.

also if someone knows about baxandall circuits/theory, i would have some questions about the "cutoff frequencies", since the variation of gain is continuous, the +/-3dB frequency varies, depending on the amount of feedback.
so is the cutoff frequency the one we find when the pot position is fully clockwise or fully counter clockwise, or is it something completely different?

cheers

[GibsonGM]

Anderton Freq Booster is a prime candidate for what you are describing.

Check out this link:  http://www.diystompboxes.com/smfforum/index.php?topic=65585.0

2nd post down has the schematic....set it up using the 90Hz values and there you go!  GREAT little circuit!!    Feel free to play with the cap values to tailor the frequency response to your taste.  MUCH better than any kind of tone stack-derived boost I've seen....bandwidth is such that is is "more musical, nicer to the ear" IMO.   

[Frances Rhodes]

great!! thanks a lot!

do you think it could be used to give a little push to what's lost (or lowered) using a guitar pedal on bass instead of changing the amp EQ, like that:
bass > guitar pedal > low freq booster > amp
?

[thelonious]

do you think it could be used to give a little push to what's lost (or lowered) using a guitar pedal on bass

It certainly could, but it might be a better solution to mod the guitar pedal (especially its coupling caps) to allow more bass through. Modding the pedal = lower noise and simpler solution, but might change the sound of the pedal in other ways. Building a separate circuit = more noise and more complicated, but might preserve the original sound/gain structure of the guitar pedal better.

[GibsonGM]

do you think it could be used to give a little push to what's lost (or lowered) using a guitar pedal on bass

It certainly could, but it might be a better solution to mod the guitar pedal (especially its coupling caps) to allow more bass through. Modding the pedal = lower noise and simpler solution, but might change the sound of the pedal in other ways. Building a separate circuit = more noise and more complicated, but might preserve the original sound/gain structure of the guitar pedal better.

+1    If you're going to 'dedicate' the pedal to bass use, I'd modify the pedal.   But for occasional use, this would be a good and non-destructive way to bring back some bass.    Or to enhance any rig that needs some more bass!   

For use with bass, you may want to increase the cap from .22 to .33 or even .47 - play a little bit on a breadboard to get the frequency dialed in a bit before you make it permanent.     

I have 2 of these around, bass and low mids, to perk things up when needed....

[Frances Rhodes]

do you think it could be used to give a little push to what's lost (or lowered) using a guitar pedal on bass

It certainly could, but it might be a better solution to mod the guitar pedal (especially its coupling caps) to allow more bass through. Modding the pedal = lower noise and simpler solution, but might change the sound of the pedal in other ways. Building a separate circuit = more noise and more complicated, but might preserve the original sound/gain structure of the guitar pedal better.

+1    If you're going to 'dedicate' the pedal to bass use, I'd modify the pedal.   But for occasional use, this would be a good and non-destructive way to bring back some bass.    Or to enhance any rig that needs some more bass!   

For use with bass, you may want to increase the cap from .22 to .33 or even .47 - play a little bit on a breadboard to get the frequency dialed in a bit before you make it permanent.     

I have 2 of these around, bass and low mids, to perk things up when needed....

actually, my purpose is to add this circuit to the pedal as a mod because the pedal i want to use is a distortion. i read many many articles and tried several bass fuzzes and distortions, none of them sounded good to me. always very "fizzy", cold and all lacked body. i can easily get bigger sounds with a guitar and a regular big muff, that's really surprising!
but i saw a demo of a fuzz pedal (forgot its name...) with 2 filter sections, one before and one after the fuzz circuit, providing 4 types of filters (if i remember well...) and i remember it sounded great, that's why i was looking for a bass boost circuit instead of letting more bass in so that i can bring some body back and not get that "muddy" sound everyone talks about when using modded guitar distortions.
one thing i would like to try also is jack orman's booster but the tube version at a high voltage, and use 2 of these to make an overdrive, that way i don't think i would need to add a bass boost but that would be a different topic!

anyways, thanks for the great advice, i'll definitely try this as soon as i can!!
cheers