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Old 1st May 2012, 11:10 AM   #1
diyAudio Member
 
Join Date: Mar 2006
Location: San Juan
Default Volume attenuator resistance question

I was under the impression that I could measure a variable resistance thru the RCA input in my preamplifier with a meter as the attenuator was rotated. The attenuator is connected to this input.

Well, it turned out the resistance was the same irrespective of the control rotation.

I was expecting to have a zero to 50K reading, so how is the signal attenuated then? Or, am I doing something wrong.
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Old 1st May 2012, 11:15 AM   #2
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Join Date: Sep 2004
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you are doing something wrong

Without doing a drawing, imagine the RCA input going to the TOP end of the potentiometer - so one will measure 50K (or whatever) to ground.

The WIPER then goes on into the amplifier. allowing a proportion of the signal from 100% to 0% to pass through, without affecting (loading) the source.
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Old 1st May 2012, 11:43 AM   #3
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Usually that wiper tapping is connected to the next stage with a series capacitor.
That capacitor appears to DC as an infinite resistance.

A meter measuring at DC will simply measure the resistance top to bottom of the vol pot and ignore what is beyond the DC blocking capacitor.
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