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Having A Brain Fart Need Some Help


Nalo1022

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While playing around with tone mods I decided to make it a high pass filter. When I went to implement that on the guitar my brain locked up. A tone pot is wired up to be a low pass filter correct? Here is my dilemma:

This is a low pass filter

172px-RC_Divider.svg.png

but I see the tone pot as being wired like this

tonecontrol.png

for a tone pot to be a low pass filter shouldn't it be like this

lowpass.png

instead of this way, which is the normal method?

normaltone.png

I tried to supply images so everyone knows what I'm getting at. I know I mentioned that i was playing with high pass filters, but first I want to know if I'm correct. Is a tone pot not wired as a low pass filter? Also would my diagram work as a low pass filter. If not what is my brain missing?

Edited by Nalo1022
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the problem is your only looking at the very begining of the circuit. thats why it doesnt look like a standard low pass filter it took me a while to get that though my thick skull i kept trying to make a high pass filter my self i thought ansil's design was too complicated. but when you think off the guitar and amp as one large circuit and the guitars electronics being just one small part at teh begining it will make a little more sence.

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I understand that one has to consider the entire chain as a whole, but that is not what I am talking about. I want to to know what is accomplished with wiring a tone circuit the way it normally is. I was under the impression that it was a low pass filter, but the way it is wired up seems off. I am not looking for an example of what to use, but more an explanation of what and why the tone circuit is wired the way it is.

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The reason it is wired as shown is thus: you are putting a variable resistance between your signal (going out the jack) and ground. How much resistance before the capacitor (the pot) determines how much of the signal from your pickups gets sent through the capacitor to ground. The capacitor then allows the high frequencies to pass through to ground with much less impedance than the low frequencies (the impedance of a cap is 1/(jwc) where w is 2*pi*f and c is capacitance), so it forms a low pass filter (meaning the lows are passed to the amp while the highs are bled off to ground). This is just a very rudimentary explanation, but hopefully useful.

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I have considered your conundrum for about 2.5 minutes (it took me a bit longer than otherwise, as I was fabricating a large one)

during this short time I've established you don't know your R's from your elbow ;-)

Let me explain...the 'R' in your posted 'classic low pass filter' diagram is NOT the 'R' in play wrt a guitar tone control. The 'R' in play wrt a guitar low pass is the DC resistance of the pickup combined with the parallel resistance of the volume pot.

Therefore...

Pickup DC resistance + parallel resistance of the volume pot (this'll be the 'R' bit)

|

|

tone cap (this'll be the 'C' bit - albeit the resistance of the tone pot effects how much impact the cap has)

|

|

ground.

which should now look like something akin to your classic low pass circuit.

Scoop 'n Daddy....I have exorcised the demons....this thread is cleeeeeeeaaaaaaan.

Edited by big_boleros
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http://www.projectguitar.com/tut/blendmod.htm

check this out its a high pass filter but be warned Ansil is kinda bad about talking over your head but it works.

i put one in my strat i actualy find it more useful that the normal tone knob.

lol terribly sorry bro i never mean to talk over someones head but i am quite tall................. :D

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lol man i am not hurt or nothing i actually wanted to see how many people would get the tall reference. and then see of those would get the other meaning of tall. from the 1930's slang........... they didn't say "high" they would say "oh him? hes just tall......." :D

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