Plz advise on balanced pot wiring - diyAudio
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Old 13th March 2012, 12:20 AM   #1
spazz is offline spazz  United States
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Join Date: Feb 2011
Default Plz advise on balanced pot wiring

Hi all-

I need to wire a pot (4 gang, bolted to a small metal enclosure) for a quick-n-dirty volume control for a balanced stereo interconnect. Using a shielded twisted pair cable for each channel, i will split the pair between two gangs, and do the same on the output of the pot. My question is about the ground:

Do I need to have the ground leads on the pot all connect to a central point, to which I wire the input shield, as well as the output shield?

If so, do I maintain 2 such points for the left and the right channel, or do I connect the two separate shields together?

The alternative being, to split the incoming shield in half, send one half to the + gang on the pot, and the other half of the shield to the - gang. Further, wire the outgoing shield to the same ground leads in the same way??

Thank you much!

PS this is the box i am using...

Click the image to open in full size.
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Old 13th March 2012, 12:51 AM   #2
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Join Date: Sep 2004
Location: hobart tasmania
Hi spazz
Here is info on attenuator pads;
Uneeda Audio - Build your own attenuator pads

In balanced configuration, Ground is not part of the signal path, rather it is a shield. Separate paths usually called Hot and Cold represent the signal paths. a balanced L pad, called a U pad ( visualise by turning the U a quarter turn to the left ) when it is balanced, is the easiest connection. To do that place fixed resistances of 1000 ohms as R1 on Hot and 1000 ohms as R2 on cold then vary resistance after the junction of R1 and R2 - and between those points to 20k or more.

Cheers / Chris

Last edited by Chris Daly; 13th March 2012 at 12:57 AM.
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Old 13th March 2012, 12:13 PM   #3
DF96 is offline DF96  England
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Join Date: May 2007
If the pot has a ground tag, presumably connected to a metal case, then this can be connected to the in and out screens. The pot track and wiper connections should be kept quite separate, and wired to the signal pins.
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Old 13th March 2012, 12:34 PM   #4
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Wiring unbalanced resistors into your balanced impedance connections will ruin the sole advantage of the balanced impedance topology, namely rejection of common mode interference.
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regards Andrew T.
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