Help me out designing two simple filters

[soggybag]

I'm working on a circuit with two parallel fuzzes. I want add a simple tone control on the end of each. On the first I want high  pass and on the second I want to use a low pass. I'm trying to find some values that will fall in a useful range.

The goal is to make a box with two fuzzes inside each with it's own drive and tone control and a mix on the output. I'd like one fuzz to work with the lows and the other to work on the highs. I'm figuring the one tone control can roll off the lows while the other rolls off the highs.

[CountryBoyAtHeart]

I'd use the stupidly wonderful tone control I'd do the 2nd one, and instead of a cap for the lowpass, use an inductor/choke. I think you'll need a buffer to split the signal path as well. If you look at the beginners equations thread there's stuff of reactances, I'd find values for them that will have medium/high impedance to the frequencies of your choice. You should have a rough idea of the frequencies you'll want to pass. But by connecting a lowpass and high pass in parallel, you can easily scoop or boost mids in reference to the other frequencies, so that should be a key focus as far as values are concerned. Of course doing it passively doesn't actually boost, but rather less cut that other frequencies.

[soggybag]

Thanks for the reply. I forgot about this page, that's a good idea fro the treble side.

Is there an equivalent low pass control? I'm not sure how to modify this to be a low pass.

[CountryBoyAtHeart]

Instead of using a capacitor, use an inductor. They do the opposite of each other, one only allows high frequencies, the other only allows low frequencies to pass through. 500uH should work nicely, if it seems odd, try a 250uH and 1000uH inductor

[earthtonesaudio]

SWTC#1 on the Muzique.com page is a lowpass, but SWTC#2 is a highpass.  The first uses a cap to shunt high frequencies to ground, the second uses a cap to allow high frequencies to go "around" the series resistor, so lower frequencies see progressively more voltage division.
I would avoid using an inductor unless nothing else will work.

[effdub]

I would avoid using an inductor unless nothing else will work.

Interesting. Why do you advise this?

[CountryBoyAtHeart]

The inductor cuts both bass and treble, and adds hiss.  Not ideal, and if I were to box this up I'd omit it altogether.

This is probably why. I haven't worked with inductors much outside of wahs, so I can't really comment much.

[earthtonesaudio]

I was actually thinking of why inductors are avoided in general.  I'm really not sure why mine added hiss in that past experiment, though I suspect the lack of shielding as the culprit.

The reasons most people avoid them are:
Physically large
hum pickup
expensive
difficult to find in large values (the 1/2 Henry typical value for a wah is a notable exception)

There are some specific cases where NOTHING else will do (such as many switching power supply designs), and some aesthetic points of view will call for an inductor because that's what is traditional (such as most wah circuits), or because it reduces circuit complexity or parts count.  But most of the time you can do what you want without using an inductor.

I'm not saying inductors are evil or bad, just a bit inconvenient.

[CountryBoyAtHeart]

I'll agree with wound inductors, but for simple chokes, http://futurlec.com/Inductors.shtml has a ton. Should be fine for stompboxes yes? and Sbe sell that wind your own inductor kit, I did it, takes like 45 minutes of time (really handwound), but better than my fasel imo.

[effdub]

Sbe sell that wind your own inductor kit, I did it, takes like 45 minutes of time (really handwound), but better than my fasel imo.

You had wire and wax and all that on hand? Amazing. 

[CountryBoyAtHeart]

I didn't wax, nail polish is a very cheap and usable potting method. but yeah, I had the wire bobbin about a foot from the potcore, winded it (the bobbin spins as you go from the little friction it gets on a tabletop) and as the wire's bobbin got too close I'd push it back while unwinding it a bit, and started over; I wouldn't wind a pickup with this method, but for a little wah inductor it works great. Good activity for while watching tv.