I replaced the tubes in the my Blue Voodoo today as it had quit producing sound a while back, presumably because the tubes had become microphonic. However, after changing the tubes, all I am getting is a very faint output which is almost inaudible. The amp is powering up normally and all the tubes are warming up, so I'm certain it's an internal issue. Any ideas as to what the issue might be?
If it's out of warranty then you should pop it open and take a look to see if anything is damaged or loose.

Also, for future reference, microphonic tubes tend to make a ringing sound, feed back endlessly, and generally amplify any mechanical noise you introduce, but they still amplify your signal properly.

Tubes don't usually fail completely and stop outputting a signal unless the filament wears out or the tube red-plates, the latter of which can damage your amplifier. In fact, you may want to look at the old tubes and see if any are burnt or damaged in some form on the inside, and pay close attention to the tube sockets when you open the amp.

You also should make sure you clean the tube pins and sockets whenever you replace them so you're not getting a marginal connection anywhere.
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Last edited by Mike-T93 at Jun 21, 2010,