is this a sign my tubes are going microphonic?

[Christopher Caruana]

So ive been doing some expeimenting with my various OD pedals and I noticed something, when I activate my pedals (even with the drive low) I get this REALLY BAD squealing. Its not even feed back, its just really bad high pitched spueals. I have ruled out my pickups because I plugged in a different guitar and still the same thing. I also tried different cambles, lowering my pickups.......is this a sign I need some new pre amp tubes?

[Christopher Caruana]

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

anyone??

[GuitarDoc]

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

Sounds like it to me. If you've got a new 12AX7 laying around, start replacing one tube at a time and put it through the tests that you've done so far with each tube, and see if you can locate the culprit.

[frankfalbo]

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

So you put a SS overdrive in front and the tube amp squeals?

[Christopher Caruana]

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

So you put a SS overdrive in front and the tube amp squeals?

well the amp doesnt squeal when im playing into just it by itself. It only squeals when I use pedals in front of it

[Chickenwings]

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

cant hurt to try...12ax7s are cheap.

[ericmeyer4]

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

Have you tried ruling out each pedal and each cable in your signal chain? And have your checked your batteries? Tried plugging into a different wall power outlet?

[Christopher Caruana]

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

Have you tried ruling out each pedal and each cable in your signal chain? And have your checked your batteries? Tried plugging into a different wall power outlet?

I dont run an effects chain because I usually run right into my 800. Ive tried my SD-1, TS9DX and my rocket fuel each by themselves and each one of them gets real nasty squeals when I turn them on......even with the PA volume on my 800 at 2. It might also be the AC adapter im using too, since I only run one pedal at a time, I dont use a 9 volt, i just use an ac adapter. I havent tried plugging into different outlets yet though.

[richard parker]

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

Have you used pedals with this amp before without it squealing ? Are you using the pedals to boost volume as well as gain ? An overdrive pedal can introduce a lot of extra gain from it's volume control even if the drive/gain control is set to zero. Use one overdrive pedal and set the controls to zero. Gradually introduce the volume so that the pedal is no louder than the amp by itself. Then introduce gain making sure that you don't make the amp any louder than it is normally. If it doesn't squeal then I don't think you have a problem with tubes. Are you using the amp set clean or are you using overdrive pedals into an already overdriven amp ? To be honest it sounds like too much gain rather than a tube issue but I could be totally wrong.

Also, try turning the amp up to high volume with nothing plugged in and, very gently, tap each of the tubes with a fingertip. If you've got a microphonic tube it will be easy to hear which one it is.

[Christopher Caruana]

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

so i found out that the v1 tube on my 800 is the one that is microphonic because I turned the amp on and tapped all the PA tubes and the 1st one i could hea through the speakers, so i tried 5 different tubes and all 5 of them i could hear through the speakers.....does that mean thee is something wrong with the v1 socket of my 800?? because i highly dought that all 5 of my PA tubes were microphonic.

[richard parker]

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

Try the first things I suggested before you start worrying about the tubes.

[astrozombie]

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

if your amp is fine without the pedals, stop messing with your tubes man!

[Koreth]

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.

[guitfiddle]

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?

[ericmeyer4]

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.