I've got a Carr Rambler with some NOS late 1960s tubes in it. I've recently noticed that when I play a few certain notes (for example, an open A string), there is a bit of noise behind the note being played that sounds roughly like the sound you'd get if you were blowing into your partially closed fist on a cold day (to try to warm it up).

It's faint, but it's there.

But it's only there on a few notes (most of which are in the lower registers). And it stops before the string has stopped vibrating.

It doesn't seem to be related to string height but I haven't gone crazy testing that or anything.

It's not a big deal because I do have to listen for it to hear it most of the time (though it's more prominent on the open A string). It's just sort of annoying. I don't know if this is a recent occurrence or something long-term that I've just not noticed before.

Anybody have any ideas?

I have a Rambler, an earlier one from before the change to the silver cord around the front. I'm using the stock tubes, but for what it's worth I've never heard a noise like the one you've described.

David

Easiest thing to do is tap lightly on the glass of each power tube with the eraser end of a pencil. In your case, you should play the open A string and tap the tube while the noise is happening. If the noise changes while you're tapping a certain tube, that tube is most likely the culprit. If your amp is making noise even when you're not playing, it's the same thing -- the noise will change when you tap on the bad tube. A good one should remain quiet. If you find one that's noisy, take it out and stick in a new one and see if your problem is resolved.

If your amp has pre-amp tubes, they can start making weird noises, even like the one you describe, when they start to go bad. Don't bother with the tapping method with these tubes -- just take a known good replacement tube and swap it one by one with each pre-amp tube. After each swap, see if the problem remains until you find the offending tube.

Another source of noise that's easily resolved are pots that have become dirty/oxidized because they haven't been used in a while or they've remained in one position for a long time. If possible, clean them with electrical contact cleaner -- if they're sealed, just turn each knob back and forth 15-20 times each throughout its entire range -- you'll hear the dirty ones -- they crackle on the the first few turns and then the crackling slowly disappears after each turn.

Try what redavide says, and if that doesn't work:

http://tubedepot.com/

Send him an email with a description of the problem. He's been helpful with me and he carries very good tubes. Prices are reasonable.

Hopefully it won't come to that.

Thanks guys. I'll give this stuff a run this evening. Just seemed super-odd to me that the "issue" would only present itself on a few notes (the same ones, consistently) across the fretboard. Just doesn't seem to like those frequencies right now ...

Will keep you posted.

Maybe those notes are the resonant frequency of the amp, and the added vibrations shake the tubes, and the shaking reveals itself as that kind of added noise...

quote:

Originally posted by elambo:
Maybe those notes are the resonant frequency of the amp, and the added vibrations shake the tubes, and the shaking reveals itself as that kind of added noise...

Given that it only happens with a few notes, something like this seems (to me) to be a lot more likely. And again, it's very much in the background. You'd never hear it in a mix and I doubt it would even be present in a recorded track.

Nothing showed up with the power tubes last night. I'll play around with it a bit more and see what happens.

It sure sounds like a tube-related problem.