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Audible Illusions Tube Pre-Amp Hum- Help Diagnosing

Began getting a low-level hum from the pre-amp which stays at the same low volume no matter where volume pots are set.  Both channels are affected, although it seems to have begun in one channel (or maybe it had been more noticable in one channel, or maybe it was my imagination.)

Is this a tube thing, a ground thing, or some other issue?  

Would like to narrow down possibilities before tearing apart the installation and/or buying tubes or other things unnecessarily. 

Thanks in advance for any guidance.
jimbo3
newbee
4,767 posts
 
You are right re tube noise being static and ground hums being varible depending on volume setting. I was just trying to simplify. If you have them on hand, it is more simple to change out the small tubes and see what happens.
audioconnection
1,271 posts
 
Mute the unit
 If it still hums let me know
Move the outboard power supply away.
Move the unit farther away from what is under it or above it.
Try 2 new shielded cables from pre amp to Power amp
If you have Cable tv disconnect the feed from the cable box to the pre
 if it goes away you need a Transformer on the cable coax in line.
 Best JohnnyR 
oddiofyl's avatar
oddiofyl
3,700 posts
 
I have a C-J that uses a 6922 tube.   I had the same symptom.  Replaced tube and it was quiet again.  Used Gold Lion 6922, excellent tube.  
pasaarun
2 posts
 
Not sure whether this thread would still be seen. I have the same issue and if I mute the unit, the hum/hiss/buzz goes away. It is more of a static sound. I am going to try to take the tubes out and clean the socket with deoxit and see if that solves it.
audioconnection
1,271 posts
 
(((It is more of a static sound. I am going to try to take the tubes out and clean the socket with deoxit and see if that solves it.)))

Don't gum up things inside there.
 unplug the unit from AC
 Just use compressed air.
 install a new set of 6 H 23 tubes if
you are still getting static after that install a better pair of shielded cables.
  Dont forget this unit inverts polarity swap both speaker wires at speakers.
Best JohnnyR
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