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Title: Low pass filters
Post by: Narcosynthesis on March 16, 2004, 04:23:54 AM

if you saw my posts before you would know i am making a stompbox for a school project

for this i need to split the signal into two halfs, treble and bass, i intend doing this by boosting the signal, then putting half through a low pass filter, and half through a high pass filter

anyone got any ideas on how to make the filters, i have a few diagrams but i dont really know how good they are or how to choose teh component values

the frequency's i want are 800Hz or less for the bass, and 600Hz or hihger for the treble

any ideas?

David

Title: Low pass filters
Post by: SaBer on March 16, 2004, 04:32:30 AM

http://www-k.ext.ti.com/SRVS/CGI-BIN/WEBCGI.EXE/,/?St=65,E=0000000000005171349,K=5305,Sxi=2,Case=obj(26886)

Title: Low pass filters
Post by: Ge_Whiz on March 16, 2004, 04:34:56 AM

http://sound.westhost.com/project09.htm

You'll need to build the 24 dB per octave version, and download the L-R calculator at the bottom of the page to calculate R and C values. It works, I've done it (although 600 Hz seems on the high side to me).

Title: Low pass filters
Post by: brett on March 16, 2004, 05:26:58 AM

This might be too simple for what you're after, but the Big Muff Pi (I kid you not) has a tone control that mixes 2 signals that have been split into bass and treble components. There's schematics of the BMP over at generalguitargadgets.com and tonepad.com. You'll see a section with a 100k potentiometer, which does the mixing. The 2 resistors and two capacitors before the pot so the low and high passing. (Low pass has the capacitor to ground, and high pass has the resistor to ground). The cutoff frequncy can be calculated from fc = 1/(2.pi.R.C) where R is in ohms and C is in farads and pi=3.14.

Sounds complicated, but it only involves 4 components and might do what you are after.

good luck

Title: Low pass filters
Post by: Narcosynthesis on March 16, 2004, 08:38:06 AM

Quote from: brettThis might be too simple for what you're after, but the Big Muff Pi (I kid you not) has a tone control that mixes 2 signals that have been split into bass and treble components. There's schematics of the BMP over at generalguitargadgets.com and tonepad.com. You'll see a section with a 100k potentiometer, which does the mixing. The 2 resistors and two capacitors before the pot so the low and high passing. (Low pass has the capacitor to ground, and high pass has the resistor to ground). The cutoff frequncy can be calculated from fc = 1/(2.pi.R.C) where R is in ohms and C is in farads and pi=3.14.

Sounds complicated, but it only involves 4 components and might do what you are after.

good luck

So would i be able to split this into two.
cap then r to ground then into the treble side, r then capto ground into the bass side, so instead of having a pot to blend the two after, keeping them separate

and are these calculations right...
fc = 1/(2xpixRxC)
-> 2xpixRxC = 1/fc
-> RxC = (1/fc)/2xpi

or have i got it wrong somewhere
from there, do i just make up a nice looking ratio that gives me the answer to RxC

David

Title: Low pass filters
Post by: bwanasonic on March 16, 2004, 12:34:39 PM

If you decide to play around with the BMP tone control, be sure to get the Duncan Tone Stack Calculator:

http://www.duncanamps.com/tsc

Educational and free!

Kerry M

DIYstompboxes.com

DIY Stompboxes => Building your own stompbox => Topic started by: Narcosynthesis on March 16, 2004, 04:23:54 AM