Odd noise in a champ

[Noval_novice]

Hello all! I just recently began to be interested in building amps. My first, a 5F1 build, sounds great overall but there is an annoying "tambourine" like sound when playing at high volumes or when playing certain notes (e.g. 12 fret, G string). I thought it was mechanical, but have tightened down every nut I can find to no effect. I've also swapped preamp and poweramp tubes with no effect. Just looking for some pointers?

[xtian]

"Tambourine" sounds like a rattling tube, and no amount of "tightening" will completely solve it.

The best test is to plug into a separate speaker cabinet so the speaker doesn't rattle the tubes. Do you still hear it?

Tube rattle has been audible in every combo I've ever played, and it always bothered me, so now I only play separate heads and cabs…but it's fun to mix and match!

[Phil_S]

Agreed on tube noise. Agreed on combos being vunlnerablet to it. I've got a pair of Sovtek EL84's that rattle on A. It happens. I use them for testing. 5F1 only has two tubes and a rectifier. See if a tube swap will help. BTW, don't discount the rectifier. I've got a Mullard EZ81 that does it. How disappointing it that?

[Noval_novice]

Thanks for the input. I had noticed just today that if I physically push down on the rectifier, the problem is much less noticeable. I will try a tube swap in the rectifier and see if that helps any.

[KellyBass]

If it turns out to be the rec tube, you might try one of those spring clamp hold down retainer gizmos for this tube. I had to use one recently on an octal valve junior...to keep the el34 from flyin' out Worked great!

A rattling mullard ez81 is a bummer indeed....

[Phil_S]

A rattling mullard ez81 is a bummer indeed....

Yeah, it must have something to do with it being GE badged It's a pretty black plate, seam on top, perfect printing, says made in Gr Britain. You can hear the rattle when you hold it to your ear and tap it. I don't know how it made its way past QC.

[Structo]

Another trick I learned here, is to take some heat shrink tubing of the proper diameter and cut a piece long enough to cover the top 1/2 of the tube, then heat it gently to shrink it.

It seems to work better than the O ring type which I have used on a Carvin Belair amp I have.

Usually it is filament rattle that makes the noise although it can be other components in the tube as well.

As mentioned a combo amp is a torture chamber for tubes but I would think a low powered three tube Champ would not be the worst offender.

[Noval_novice]

So I replaced the cheap Sovtek rectifier with a JAN GE tube and the sound is mostly gone. Now I can enjoy my first combo. Thanks, guys.

[Phil_S]

Another trick I learned here, is to take some heat shrink tubing of the proper diameter and cut a piece long enough to cover the top 1/2 of the tube, then heat it gently to shrink it.

It seems to work better than the O ring type which I have used on a Carvin Belair amp I have.

Usually it is filament rattle that makes the noise although it can be other components in the tube as well.

Are you saying this will work for a rectifier? My impression is, they get pretty darn hot. Will the heatshrink eventually start to burn?

[Structo]

No I think it's mostly used on preamp tubes.
I wouldn't put it on any octals.
I have used the O rings on EL84's before.

[Phil_S]

Yeah, what I thought. A 12AX7 almost stays cool enought to grab it bare handed (don't try it). A 6CA4 is really going to cook, along with just about any power tube. I might get some O rings for that rectifier to see if it can be salvaged. Thanks.