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Old 1st May 2012, 11:10 AM   #1
diyAudio Member
Join Date: Mar 2006
Location: San Juan, Madrid
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
diyAudio Member
Join Date: Sep 2004
Location: South Coast, UK
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 online now AndrewT  Scotland
diyAudio Member
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.
regards Andrew T.
Sent from my desktop computer using a keyboard
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