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Random pop sounds in my system are scaring me

Hi, I need some help and expertise on this potentially expensive situation! The last few times I've powered up my 18wpc SET amp it has been plagued by some startling "pop" sounds at random intervals. The amp switch is in the mute position, with no source selected and yet at random intervals I hear an alarming pop sound coming from the speakers. The volume of the popping isn't SUPER loud, but it does startle me and has me worried. The weird thing is, sometimes it happens, sometimes it does not. I'll have to do some more testing, but I haven't noticed this happenig when a source is actually playing through the speakers. When I bias the tubes immediately after hearing a pop, I don't see any weird numbers or behavior on the bias meter. The amp is only about 3 months old and it took so long to get, I'd hate to lose it! I know it could probably be a million different things, but does anyone have an idea of what might be happening here? Help!
Thanks!
mbleming
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lak
4,550 posts
 
I agree sounds like a bad tube.
As Beerad and Jaiello said try the tube swap and post the results.
mbleming OP
33 posts
 
First, thanks to everyone who has offered their help and expertise on this, I'm new to tubes and need all the help I can get. I played around a little bit last night and I could reproduce the pop when I plugged and unplugged my phono stage. The weird thing is, it didn't happen every time! I have no idea what it could be, does the problem lie with the amp itself or my wall outlets, or both? Again, this is a new problem, only within the last week. It's strange because I was hearing it on its own, withough plugging or unplugging components...only today it happened when I plugged/unplugged my phono stage.
rodman99999
6,035 posts
 
Are you saying that you are plugging in and unplugging your interconnects with the equipment turned on, and selector turned to that input? That's never a good idea, and will always result in a "pop". Lots of potential for sending an unhealthy transient to your speakers. Have you tried any of the above suggestions regarding your tubes?
mbleming OP
33 posts
 
No, no, I'm not unplugging the ICs, just the power unit to my phono stage and I haven't done the plug/unplug thing with a source selected...the times I've heard the sound, the amp's source select switch has been in mute! I've tried tapping the tubes lightly, but nothing. Its a strange problem as it seems very random, other than today when I plugged in my phono stage.
steidlguitars
90 posts
 
Yet another vote for a power tube going south, just happened to me the other day (grumble, grumble).

Do you have a spare? If so, change out the tube or tubes in the channel where the pop is occurring.
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