Need help with Dr Boogey - mods for bass guitar

[kalin1981]

Hi and sorry for my bad english. I use "search" but not find how to solve my pproblem. Sorry if im in wrong forum too.
Im beginner in electronics,  but i build 2 dr boogey`s for my friends guitarist. The pedals running without problem, i use schematick from gaussmarkov site.
Now wana make one for me, but im playing bass guitar. What mods i need? Use passive PJ configuration bass, and one with albert kreuzer onboard preamp, PJ too. Please, explain me what parts i need to change? Maybe some caps, but please tell me not just to change this and this cap or resistor, but why to change it. I wana using my head, not just copy-paste schematics. Thanks

[Mike Burgundy]

A capacitor acts as a high-pass filter - it lets through higher frequencies more easily than low frequencies, and DC voltage (basically frequency = 0) is totally blocked. A cap of higher value lets through lower frequencies. Where exactly the caps starts to "open up" is detemined by that caps value and the resistance coupled to it - google something like RC formula (R for resistor, C for cap). Formula goes f=1/(2πRC)
With that in mind you can figure out which caps are important for the sound - mostly coupling caps and the tone control. Start out with doubling those to half the frequency - one octave down. That'll get you started. Figuring out which ones exactly does involve knowing/learning what each cap is *for* - a coupling cap has significant impact, but a tiny feedback cap filtering out supersonic radio interference or a power supply filter cap don't need to be changed.
That said: adding distortion changes *everything*. Experiment. Sometimes it sounds better *not* to let in all those lows to be clipped (end up with a fart sound). A big muff is a great example - it's notorious/famous for it's big fat sound and loved by bass players - and it filters the lows so they're not clipped. Because everything else is clipped (and thus limited to a lower level), the lows come back for a big fat result.

[Giglawyer]

I suggest you socket the input and output capacitors, so you can swap different values in and tune in the sound you are looking for.  If that's not an option, build a paralooper (see this excellent article - http://moosapotamus.net/paralooper.html) and just use it in conjunction with the Dr. Boogey.