Volume attenuator resistance question

Manolo47 · 1st May 2012, 11:10 AM

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.
Thanks

cliffforrest · 1st May 2012, 11:15 AM

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.

AndrewT · 1st May 2012, 11:43 AM

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.

1st May 2012, 11:10 AM	#1
Manolo47 diyAudio Member Join Date: Mar 2006 Location: San Juan	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. Thanks

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1st May 2012, 11:15 AM	#2
cliffforrest diyAudio Member Join Date: Sep 2004 Location: 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.

1st May 2012, 11:43 AM	#3
AndrewT 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.