#1
I have an ENGL Powerball. The tubes are almost a year old now I think. I rarely play it very loud, and I have only gigged with it once. I'm playing in the local church tomorrow, and I brought my amp up there this evening just to set things up. Then I get this horrible squealing feedback. It sounds just like if I had my gain on 10 and played on max volume, but it happens at really low volumes too, and I keep my gain at about 3-4, it's never been like this before. I tried moving around, moving the amp around, using different power outlets - nothing worked. The feedback didn't appear on clean or cruch, only on a typical high gain setting.

So I called a friend of mine and asked him what to do. He told me to tap the tubes with a pencil. I did, but there was absolutely NO sound coming out when I did that. From what I can tell, all the tubes light up the way they are supposed to. While I'm actually playing there is no feedback.

So, do I have a microphonic tube? Is it SAFE to play it tomorrow or should I just bring my microcube and scare people away with crappy tone?
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#2
Go to the music store, pick up a preamp tube, and swap it out in all positions to see which one is microphonic. That is the only sure way of finding out.
#3
I thinkthere's a test where you tap the tube eith a pencil lightly, ask Dave_MC h know A LOT about tubes.
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#4
Quote by al112987
Go to the music store, pick up a preamp tube, and swap it out in all positions to see which one is microphonic. That is the only sure way of finding out.


The only problem is that I don't have the time to do that before the concert tomorrow. Should I just stay on the safe side and use my microcube?
Guitarist and composer of the band SHADOWMIND. Check it out:

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#5
Quote by Fat-bastard0603
I thinkthere's a test where you tap the tube eith a pencil lightly, ask Dave_MC h know A LOT about tubes.


That is EXACTLY what his friend told him to do, did you read the post?

TS: I'd play it safe and use the MicroCube, but try the amp again and see what happens. Are all the tubes lighting up properly?