Suggestions for bass boost with narrow frequency range

[joeychickenskin]

Hi

I'm thinking of running an ABY box with a guitar signal with A straight into a guitar amp and B into a digital octave down pedal into a bass amp.

I'll be playing mainly part-chords (two-three finger power chord punk songs) so there shouldn't be too much top-end information but I wonder if there is already a circuit that could emphasise and boost the post-octave-pedal signal enough so that the bass signal is less muddy by boosting what would be the frequency-range of the octave down root notes more than the rest of the chords, maybe tweakable/sweepable with a pot?

Can anyone think of a circuit that does this?

[PBE6]

Maybe I'm misunderstanding what you want, but can't you just turn up the octave pedal? Simple, direct and focused on the new notes being created. If the pedal is already at "11", you can probably just turn up the BASS on the bass amp.

[PBE6]

If you're still looking for a frequency-specific boost/cut, a parametric or semi-parametric EQ would be your best bet. The GeoFEX parametric EQ is a simple, well-known and useful circuit:
http://www.geofex.com/article_folders/eqs/paramet.htm
If you want a bit more control over the Q value, try a state-variable filter like this one from Elliott Sound Products (see Fig. 5):
http://sound.westhost.com/articles/state-variable.htm
If you just want to add some more "thump" at a specific frequency, check out the "Bottom" and "Top" controls for Runoffgroove's Thunderbird:
http://www.runoffgroove.com/thunderbird.html
The frequency is fixed and it only boosts, but it does deliver a constant Q and it's very simple to tune and implement.

[joeychickenskin]

Perfect!

Just the things I was looking for. I have a really vague notion of what a parametric control is from an old Bass amp. I'm about to find out a lot more...

Thank you