is this a sign my tubes are going microphonic?

[Christopher Caruana]

Re: is this a sign my tubes are going microphonic?

Simply getting a noise whenever you tap on the tube doesn't a bad tube make. If you get a tapping noise out of the amp's speaker whenever you tap on the tube, that's to be expected -- you're tapping on the thing! But if the only time the tube makes noise is when you tap on it, you're fine. Futhermore, it is to be expected that any tapping upon the tubes would be heard in the V1 position, as there are 2 more gain stages past V1 and a phase inverter to amplify whatever noises are passed into the signal chain to audible levels.

However, you do have a problem when tapping the tube sets it ringing. Giving a tube a tap and getting a tap sound is fine, but when the tube continues to make the noise all by itself after you have stopped tapping it, then you have a problem. If it doesn't start ringing and humming all by itself after you have stopped tapping it, it isn't microphonic. Leave it alone.

Where is your JCM800s preamp gain set? You're putting gain pedals in front of the amp. If you have enough gain dialed in on the amp, the extra gain added by the pedal could be enough set the amp over the edge and feeding back and squealing uncontrollably.

my 800 PA is set at 2 when I am running my pedals

[Christopher Caruana]

Re: is this a sign my tubes are going microphonic?

Do you plug into the high gain or the low gain input?

When you play loud clean, is there a ringing after you strike a chord, while you hold it out?

high gain input. and no i dont remember hearing any ringing or anything

[Christopher Caruana]

Re: is this a sign my tubes are going microphonic?

Also are you standing too close to the amp? Do you have anything else electronic in the room like a tv, computer, etc?

Some times standing to close to those you get weird sounds.

I am standing a few feet away from the amp. I do also have a tv, and a computer in the room. Im going to try taking the amp outside this weekend and playing it out there

[guitfiddle]

Re: is this a sign my tubes are going microphonic?

Are the pickups in your guitars wax potted? If not, they could cause a squeal like that.

Without any ringing, I'd say your tubes are ok.