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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
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.
rodman99999
6,159 posts
 
No surprise that you would hear a pop when powering up a source while the rest of the system is active. You've still not mentioned if one or both channels are making noises. If one- Have you tried the tube swap?
mbleming OP
33 posts
 
I think it's both channels, but I'm not 100% sure yet, as the last two times I've heard it I've been next to the left speaker. I haven't tried to swap tubes as money is a little tight at the moment...I'll definitely have to bite the bullet soon though, as a bad tube seems to be the most likely culprit. Its tough to figure out because the instances are so random. Also I've noticed that the pops seem to happen more or less within the first 20 mins after power up, after that point I haven't heard much. So many variables! I'd love to just move the whole thing to another room/power outlet, but this is impossible in my apartment at the moment.
kgturner's avatar
kgturner
663 posts
 
mbleming:

when people tell you to swap the tubes, they don't necessarily mean to buy a new set, they mean for you to take the tubes that run the right channel and place them in the sockets of the tubes that run the left channel, and vice versa. by switching the tubes positions in the amp, you can narrow down if it's a bad tube causing the pop as the pop will travel from one channel to the next.

now, if the popping is in both channels, it might not be a fault tube. as you stated, there are lots of variables at work. out of curiosity, what amplifier are you using?
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