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soft thump and driver moves...even with no signal

Anyone experience anything like this? Was listening to Spotify when I noticed a slight noise in between tracks. Saw the left driver move slightly then again maybe 10 seconds later or even less. No music was playing at that time. Turned volume down completely but still had the periodic movement. Similar to what you might see with a warped record. Shut things down for the evening. Hoping it's just some old tubes finally failing. Plan to change out power tubes tomorrow. Let me know if you've any insight into what might cause such a thing. Thanks in advance.
ghosthouse

Showing 3 responses by atmasphere

atmasphere's avatar
atmasphere
12,128 posts
 
Hoping it's just some old tubes finally failing. Plan to change out power tubes tomorrow.

Based on the description this is quite possibly a bad tube in the signal chain somewhere after the volume control. Its likely not a power tube.
atmasphere's avatar
atmasphere
12,128 posts
 
If this occurs fairly often, first thing to do is swap the interconnects from the preamp left for right and see if the problem moves to the other channel. If so, the problem is in the preamp. If not- its likely one of the driver tubes.
atmasphere's avatar
atmasphere
12,128 posts
 
Ha! Called it.

Its not likely that its a bad connection on the tube socket- that would sound different. Your handling of the preamp tubes has likely stopped the errant tube for a while, but my forecast is that it will be back eventually.

You swapped the preamp tubes left for right so now the problem will be back in the left channel if it is a tube.
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