Aragon 24K Volume control noise and dc - diyAudio
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Old 15th August 2014, 09:50 PM   #1
rickcl is offline rickcl  United States
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Join Date: Mar 2003
Location: California
Default Aragon 24K Volume control noise and dc

Hello. I have an Aragon 24K preamp that has a little scratchiness in the volume control in the first 1/4 turn on the left channel. I had a cheap linear pot. so I stuck that in circuit and it did the same thing. I took the original Noble pot. apart and cleaned it. It's fine.

I did measure -49mv across each the sliders to ground. I did stop all the noise by soldering in a couple of 4.7uF NP caps in series with the slider.
There are a couple trimmers close to the line amp. I was wondering maybe these are offset adjusts.
For ref: power supply output: -24.70 and +25.32

Thanks all! I am stumped....
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Old 15th August 2014, 11:29 PM   #2
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Join Date: Nov 2004
Location: Germany
Sounds like input bias current of the following amplifier stage is at fault, which would indicate either a leaky existing coupling cap or none being present at all (which would be a design issue). It's hard to tell more without a decent idea of what the circuit looks like. Seems to be a discrete affair.
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Old 17th August 2014, 05:06 PM   #3
rickcl is offline rickcl  United States
diyAudio Member
Join Date: Mar 2003
Location: California
Default Schematic available

I have the schematic now so if anyone want to take a stab at troubleshooting this one I would be really grateful.

Just shoot me a PM with your email address.

Thanks, Rick
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