Author Topic: passive tone control  (Read 1167 times)

Dimitree

passive tone control
« on: April 17, 2015, 02:49:18 PM »
hello everyone
I'm having some doubts while substituting the "filter" potentiometer in this schematic (it's the final stage of a fuzz circuit).
I don't have any 10K-LOG potentiometer, instead I'd like to use a 50K-LOG potentiometer, but I can't understand if it is ok, and if yes what value should have the capacitor in order to get the same results.



thank you!

stonerbox

Re: passive tone control
« Reply #1 on: April 17, 2015, 03:18:30 PM »
Im guessing that cap is a 0.068uF and would gradually start to cut off frequencies above 234 Hz and if you use a pot that is five times bigger (50k) than the original 10k pot you'll have to divide the caps value by five, too. In that case you'll need a cap somewhere around 0.0136uF, maybe perhaps a 0.015uf?

However if the cap is a 0.0068uF it would cut off at about 2340.51 Khz and above...
Anyways here is a great tool for RC-filter calculations. http://www.ekswai.com/en_lowpass.htm

Good luck!
« Last Edit: April 17, 2015, 03:27:33 PM by stonerbox »
"JFETs are like people.... similar,  but different from one another."
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Dimitree

Re: passive tone control
« Reply #2 on: April 17, 2015, 03:26:16 PM »
thank you
my doubts was because this doesn't look (to my ignorance) like the usual tone cut "on line" with signal. I'd expected the Level wiper connected to the junction between C4 and Filter pot. What's the difference?

btw. the cap says .68J63, isn't it a 0,68uF?

stonerbox

Re: passive tone control
« Reply #3 on: April 17, 2015, 03:32:16 PM »
thank you
my doubts was because this doesn't look (to my ignorance) like the usual tone cut "on line" with signal. I'd expected the Level wiper connected to the junction between C4 and Filter pot. What's the difference?

btw. the cap says .68J63, isn't it a 0,68uF?

I'm not sure I follow your level wiper issue here? To me it looks like a pretty standard potentiometer/cap tone cut.

At first I thought that the cap could be a 0.68uF too, but that would mean the cut off would start at 23Hz (!). Which is extremely low.. like subwoofers-does-not-even-always-go-that-low.
"JFETs are like people.... similar,  but different from one another."
- BubbaFet

GibsonGM

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Re: passive tone control
« Reply #4 on: April 17, 2015, 04:12:16 PM »
Since the top end of the pot isn't connected, it is just a variable resistor...it's the resistance between wiper and junction of C4 that's important. Otherwise, it's a very standard circuit.
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