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Passive equalizer

John36

Jun 11, 2021
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I'm looking to build a passive equalizer/ volume pedal for an electric guitar foot pedal. I want to use choke coils instead of capacitors to slow the response of the amp. Can you take a look and make sure my design is good? The coils should be 1.6H I think, but it's just an educated guess. It's basically an adjustable high pass and low pass filter.
upload_2021-6-11_10-42-58.png
 

WHONOES

May 20, 2017
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You will need some source resistance otherwise you are just shunting the output of what ever it is connected to.
Are you averse to using an active circuit?
 

John36

Jun 11, 2021
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Don't wanna do active because of voltage supply, and trying to learn electronics so I want to keep it simple.
What do you mean by shunting the output?
Here's what I ended up with.
upload_2021-6-14_11-5-14.png
 

John36

Jun 11, 2021
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Great article. I read through half of it so far. I'll get thorough the rest and get back to this.
 

VenomBallistics

Aug 30, 2018
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You really should get over your fear of active circuitry. Often times, after we hack, slash, and sculpt a signal via passive means, we encounter a need to amplify the product back to a usable level anyhow. Just embrace it
The Boss MT-2 "Covid tracking chip" has a really good three band parametric EQ to use as a springboard, even if you hate everything else about the pedal
 

John36

Jun 11, 2021
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The problem with active and boosting a signal with guitar is what are you hitting the amp with. A humbucker, as I have, puts out a hot signal that drives most any amp into distortion. I generally use a 1M pot passive volume in my guitar chain turned down about 1/2 to 2/3 to solve this. I was wanting to include some tone shaping with my volume pedal. I could do it with my guitar volume knob, but I use that for volume swells. For tone I could use the tone knob on the guitar, but I would like to make that a blend knob. So, that said, there's a method to my madness.
 

John36

Jun 11, 2021
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It looks like I need an inductance meter since I built my own choke coils. I'll get back with a schematic when I do all the math.
 

VenomBallistics

Aug 30, 2018
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The problem with active and boosting a signal with guitar is what are you hitting the amp with. A humbucker, as I have, puts out a hot signal that drives most any amp into distortion. I generally use a 1M pot passive volume in my guitar chain turned down about 1/2 to 2/3 to solve this. I was wanting to include some tone shaping with my volume pedal. I could do it with my guitar volume knob, but I use that for volume swells. For tone I could use the tone knob on the guitar, but I would like to make that a blend knob. So, that said, there's a method to my madness.
okay ... so basically you're trying to "offshore" your guitars tone control.
I can see some value in this. however, as we deviate from a simple treble bleed as we have in out guitars, we start to get outside the passive wheelhouse.
Passive methods can only make reductions and they cannot do so without having some influence the other bands, such as band shift and unintended reductions. You may require and active "sandwich" for isolation and make up gain, like we do in compressors.
 
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