Microphonic from Vacuum Tubes?

HI,  I have a question regarding microphonic from vacuum tube.  I have a Cary SLP-05, and I've changed the output gain tubes to some NOS RCA, and also recently purchased a pair of Linlai for the balanced buffer stage.

I now occasionally hear a loud pop in the music.   It doesn't happen very often, but when it does, it is quite loud.   This happens when I am streaming digital music, so it can't be those occasional pops you hear from vinyl.  

Can someone tell me if this loud pop possibly caused by microphonic in my tubes?  if so, how do I track down which tubes?   My guess there is no easy way but change one tube at a a time, which can be extremely time consuming.   Also I don't own a tube tester.  I wonder that would help tracking it down.

Also I read something about vacuum tube damper rings,  would that help calming down possible microphonic?

I still  consider myself a newbie in tubes,  so any hep will be appreciated.  Thanks very much.


@xcool OK- keep in mind to make no assumptions. That can lead you on a wild goose chase.

The first thing to do is swap the interconnect cables left for right at the amplifier inputs and see if the problem moves.

If yes => the cable, preamp or source is on the hook

If no => the amplifier is the problem.

So do that and get back to us.

Or, if the problem moved, the next thing to do is swap the connections from the source at the input of the preamp.

If the problem moves its the source or its interconnect cable.

If the problem stays put then the preamp is on the hook.

If you get to that point then you swap tubes from one channel to the other, a pair of tubes at a time. Between each swap you play the system until you can determine which channel has the bug. If it moved you know which tube is bad, if it didn't then you proceed to the next pair of tubes and repeat the process - do this until the problem moves and then you've located the bad tube.

Good Luck!

Thanks @atmasphere for your instructions.  The problem is that I think I've heard the pop from either left and right channel before, but not at the same time.   So the problem doesn't seem to be specific to a single channel.

I sure hope that this is not an issue with my Cary preamp.  I've had enough problems with it since I bought it about 7 months ago.  😀

@xcool Like I said, don't make any assumptions. Right now it sounds like you need to sort out for real which channel its in or if its in both.

If its randomly in both, FWIW I'd be more suspicious of your source... but keep an open mind. That's the first rule of troubleshooting. The second is not to make assumptions.

I would start by pulling and reseating all the tubes (rectifier included) when the amp/tubes are cold.

If the popping persists replace the new tubes with the old ones.

If there is no popping after this systematically swap in the new tubes one @ a time.

Aside from a bad tube poor pin/socket contact can cause the noise you describe.

This will take time, but it's easy.