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Level pots and degrees of attentuation
Level pots and degrees of attentuation
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Old 20th October 2011, 06:28 PM   #1
jeffreybehr is offline jeffreybehr  United States
diyAudio Member
Join Date: Mar 2005
Location: Phoenix, Arizona USA
Default Level pots and degrees of attentuation

I recently installed a quad of somewhat-expensive, hi-end TDK 50K pots in my four Marantz MA-24s.
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(One pair of amps has high-pass-filter caps installed between the input terminal and the pot.) The goal was to reduce their excessive (about 30dB) of Voltage gain and to further adjust the lower- v. higher-frequency balance.

Each amp had a 56K load resistor as the 1st device following the input jack. I removed this and installed the pot with its 50K winding from hot to ground and the wiper output to the circuitry. The input resistance is now 52K - 53K on each amp (within tolerance), and the pots work in that when turned down, the output level decreases, all the way to zero.

However, the problem is that even tho these are log-taper pots, -15dB isn't reached until about 10 clock-hours of rotation, and then the adjustments are very course, making fine adjustment of treble level about impossible.

I'm no technician or engineer, but I have a vague 'understanding' that one can place a pot between resistors to alter its range...affect...on the output level. What I'd like to try is to add a 50K resistor above or below the pot's 50K winding. I realize the input resistance will now be 100K (which is better for other reasons), and what I hope is that the amount of attentuation will be decreased and the same 15dB attentuation will be reached earlier in the rotation.

Am I headed in the right direction? Should I start with the additional resistor above the pot's winding (at the input jack) or on the bottom, to ground?

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