Help Me Understand The AMZ Presence Control

Started by SpringbokUK, February 14, 2019, 02:24:25 PM

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Hi all

So I get it, it's a standard BMP tone control that has a HPF on one side of the tone pot and a LPF on the other with a pot in series with the HPF to scoop or boost the mids. What I don't get is how if you turned the tone control all the way to the LPF side, the body control connected to the HPF still functions. I thought if there's a bunch of resistance on that side then surely the HPF nor the body control would pass through the signal? Unless it's relevant to what ohm the tone pot is? In that case if I took out the 250ka tone pot from AMZ2 and then slap in a 500ka, will there be less signal passing from the HPF side if I turn it fully to the LPF? Or will I just get a wider sweep overall? Or both?

And I'm guessing that body control is just like adding resistance to R1 of the HPF equation?

Nice one

Mark Hammer

Each side of the tone control exerts a fairly shallow filtering effect, given that each half is 6db/octave slope.  Although the resistance of the 100k Tone pot does result in attenuation of whatever side the control is turned "away" from, there is still some content getting through.  So, if one adds the appropriate resistance to the treble/highpass side, and lowers the corner frequency of that side, then as you turn from full treble to full bass, there will be a broader range of higher frequency content that still "sneaks" through.  And the same thing going the other was with the bass content.

Think of it like being able to persuade the doorman/bouncer at a club that they can let your friend in along with you, even though everybody else has to stay out in line.


Ah cool okay!
And what if I increased the value of the tone control? Just a wider sweep?


maybe. the sweep may get wider, or it may stay about the same. breadboard it bro!

to me? best mod is taking the resistor to ground out, and replacing with a 50-100k pot.
then ya got the classic mid scoop, no mid scoop, or more of a mid scoop and all ya gotta do is add one part.
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