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My Fender Twin is emitting a sound (birdlike or radio chatter interference-not loud) sound. The "idiot lights" in the back light green and everything sounds fine when playing the guitar. I turned all lights, electric devices I could to eliminate any possible interference. The sound is intermittent and lasts maybe 5-10 seconds. I spoke to someone at a large music store (repair area) and they said it could be one or more of the 12AX7 preamp tubes going microphonic. The Amp is just a year old played maybe ten hours a week at volume 2-3. I thought the power tubes wear out faster then the preamp tubes. Anybody have ANY ideas...?

Bogoboy
 

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you are right about power tubes wearing out faster than preamp tubes...at least from what I have read. I have no idea what is causing that though...sorry.
 

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Twin Noise

I would try swapping the preamp tubes. You have two channels so that may help you in locating the problem.
Try tapping the tubes and see if the bird sounds can be reproduced.
You said it happens for 5 to 10 seconds. Does it occur on a regular basis or just after power on?
You may have a microphonic tube. Do the swap thing and see what happens.
 

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My Fender Twin is emitting a sound (birdlike or radio chatter interference-not loud) sound. The "idiot lights" in the back light green and everything sounds fine when playing the guitar. I turned all lights, electric devices I could to eliminate any possible interference. The sound is intermittent and lasts maybe 5-10 seconds. I spoke to someone at a large music store (repair area) and they said it could be one or more of the 12AX7 preamp tubes going microphonic. The Amp is just a year old played maybe ten hours a week at volume 2-3. I thought the power tubes wear out faster then the preamp tubes. Anybody have ANY ideas...?

Bogoboy
Maybe it IS radio interference!

Do you live next door to a taxicab with a dispatch radio?

Ever watch the Spinal Tap movie?:smile:

:food-smiley-004:
 
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