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MP-3 issue

50.137.120.38
Posted on April 15, 2014 at 16:36:10
jumpsturdy
Audiophile

Posts: 194
Location: New England
Joined: April 5, 2002
 Recently noticed a small problem on my MP-3. The trim pot for the right channel has become noisy (scratchy sound) when I turn it. Tried cleaning it but with no effect. Would not be concerned as I rarely turn it, except in the way it manifested itself. There is almost no noise until the last third of the way around (turning from left to right) and if I move it quickly the right DC offset light briefly flickers. No noise on the other trim pot nor any flickering of DC offset. Any thoughts on this issue would be appreciated.

 

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12AU7 voltage amplifier, posted on April 16, 2014 at 08:06:16
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 If the sections of the associated 12AU7 are mismatched, they can cause the gain trim control to have noisy operation as you have described.

 

RE: 12AU7 voltage amplifier, posted on April 16, 2014 at 08:49:53
jumpsturdy
Audiophile

Posts: 194
Location: New England
Joined: April 5, 2002
 Thanks Ralph,

I thought it might not be the trim pot.

I just changed all the !2at7s to Pvanes from china and this is a good excuse to do the same for the 12au7s. Really like these high quality chinese tubes; hopefully the 12au7s will be as well matched and quiet as the 12at7s

 

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