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Old 30th April 2011, 09:22 PM   #1
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Default Help With Alps Volume Pot Noise

Can someone help me with this peculiar issue?

I replaced a cheap 100K Ohm volume pot on an tube amplifier kit with a 100K Ohm Alps Blue Velvet volume pot. With the Alps volume control at the extreme ends, near the most quiet and near the most loud, I get a slight hum with a noise, a sort of rushing sound.

Between those extremes the Alps volume control is dead quiet.

The original cheap volume pot had a similar issue but less pronounced.

This was an S5 Electronics K12G kit. I did remove two 0.22uf DC blocking caps in line with the two inputs.
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Old 30th April 2011, 09:29 PM   #2
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you can try 100ohm grid stopper. or put the DC blocking caps back.
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Old 30th April 2011, 09:29 PM   #3
ilimzn is offline ilimzn  Croatia
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You might have an oscillation problem, as well as a ground issue. The residual resistance of the Alps in both extreme positions is only a few tens of an ohm, unlike cheap pots where it's 10x more, which may account for the less pronounced effect with the cheap pot. For an experiment try connecting a ~1k resitor in series getween the pot wiper and the amp input, and report what happens.
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Old 1st May 2011, 12:48 AM   #4
Michel is offline Michel  Canada
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Make sure there is no measurable DC on the pot. If DC is present, you will always have the kind of noises you describe.
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