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Help Diagnose Tube Preamp Problem

I have a George Wright preamp along with his mono 3.5 amps. I recently started hearing some noise or crackling through my speakers at various times. When I turned the system on the other day, it was very loud for a couple of seconds, but then went away. I've done some research and "tested" the tubes by gently tapping them with a pencil, and the weird thing is the tubes in the preamp all give off a ping that is not solid like the tubes in the amps (I don't believe the tubes in the preamp all went bad at one time). Even stranger, if I tap on the metal on/off switch, this also pings through the speaker as if it is somehow getting picked up by the current. Something strange going on, anyone with any ideas of the problem? thanks
skf3636
ahendler
416 posts
 
I don't think the preamp which he is talking about has adjustable tube biasing. A lot of preamps will ping if you tap on the tubes and does not mean that they are bad. Does the pinging get worse as you turn up the volumn?
ahendler
416 posts
 
Another question. Does your preamp have the switch on the back for low and high gain? If on high switch to low gain and see if this helps solve your problem.
marakanetz's avatar
marakanetz
5,473 posts
 
I don't think it's preamp. I think it's amplifiers. Tapping tubes isn't a good idea at all.
opus88
530 posts
 
I agree with Marakanetz on both points, especially the loud crackling, which typically indicates a problem with amp output tubes.
opus88
530 posts
 
Incidentally, chances are all your amps' tubes are not bad. I've experienced loud crackling through a speaker several times before with just one of my six output tubes per monoblock being bad.
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