Pre amp tube weirdness. Or not?

[Thoth105]

Howdy,
I just retubed my XTC 101B, including the preamp tubes. Before this retube, I had been hearing buzz/rattle whatever coming from the head when I played a note. The rattle/buzz sounded more or less like what I was playing, just metallic/glassy buzz. After retubing and biasing, I still heard it. I think its v3, and I've tried 6 tubes there and it doesn't change. Put a boost in front of the amp and the rattle is, wait for it, boosted! The typical microphonic checks were negative, and the amp doesn't squeal.

The amp seems to sound fine through the cab, but I can't imagine I'm supposed to hear what I'm playing through the glass of the tube. I don't think I've ever had another amp do this. Any ideas? Could it be the EL34's rattling, and it just seems like its coming from V3?
I don't really know what "EL34 rattle" sounds like.

DB

[Pietro]

I've heard of "tube dampers"... might need to try that.

[Ray K.]

If this is a head, I agree it is unusual. Though not entirely impossible.

You mentioned testing for microphonic tubes, so I assume you've tried tapping each tube with a pencil or chopstick?

If so, it does sound like tube dampeners would be the ticket. Here's a suggestion. (http://eurotubes.com/euro-damper.htm)

Good luck,
Ray K.

[okstrat]

Do this:

Put the old power tubes back in. Does the problem go away? If so, then it's an issue with the new EL34s. If not, then it's a preamp tube for sure.

It's just a matter of being consistent with testing. If it's the EL34s, then pull half of them and see if it goes away. If it does, then it was one of the two tubes you pulled. Take whichever pair was still 'bad' and replace one. Problem goes away, it was the tube you replaced. If not, then it was the one that was left behind. Use the same method to find a bad preamp tube.

Pete

[okstrat]

Do this:

Put the old power tubes back in. Does the problem go away? If so, then it's an issue with the new EL34s. If not, then it's a preamp tube for sure.

It's just a matter of being consistent with testing. If it's the EL34s, then pull half of them and see if it goes away. If it does, then it was one of the two tubes you pulled. Take whichever pair was still 'bad' and replace one. Problem goes away, it was the tube you replaced. If not, then it was the one that was left behind. Use the same method to find a bad preamp tube.

Pete

Forgot to mention, if you pull new tubes, put the old tubes in their place. ;) Just make sure you can't mix them up.

[Thoth105]

Thanks for the suggestions folks. The rattle was there before I retubed it. That was part of the reason I did it. Now I think one of the tube sockets itself is rattling. It's a pain.

[okstrat]

Thanks for the suggestions folks. The rattle was there before I retubed it. That was part of the reason I did it. Now I think one of the tube sockets itself is rattling. It's a pain.

Could it be a cabinet resonance issue? Take the head off the cab and try again. BTW, the 101B is a fantastic amp and I love mine.

[Thoth105]

Doubtful. I have the cab in an iso box about 10' away so it isn't sitting anything making noise.

The 101b is great and very flexible. Definitely has it's guitar preferences though.

Edit: I've got a Goldfinger coming this month - I can't wait to compare the 2.

[jamme61]

did you check the speakers and try a different guitar cable too

[Thoth105]

I use several different heads into this cab and the only one that does it is the xtc. Besides, the sound is actually coming from the head, not through the speakers. I can put my head up to it and hear the sound from the amp itself.