Diagnosis nasty sustain in vintage TB

[s1m0n]

I'm stuck for a few days in a place with only an old no name tenor banjo to play, but can't play it for long because of a horrible, metallic, grinding sustain that I can't diagnose, and I don't know enough about banjo pots to know what to check next.

I've got leather damping the strings at the tailpiece, so it's not that. I can induce the ring just by tapping on the skin without touching the strings, though not when I lightly damp all 4 strings at once. The skin is one of those ones that are plastic with paper backing, and it was on when I bought it a decade or so ago. It didn't make this noise then. The skin feels very taut, but I don't have a banjo key and haven't adjusted it since I've owned it. The strings are a decade old but haven't actually been played much.

Anyone have any suggestions what else to try?

[Charles E.]

A lot of banjo players dampen overtones in the head by placing a sock or padding between the dowel stick and the underside of the head. Usually it is placed behind the bridge, sort of under the tailpiece.

[s1m0n]

Thank you. That sounds like a good idea.

[texaspaul]

If you have not tightened your banjo's head in 10 years you might want to check it.
I simple way is to place a straight edge along side of the bridge inside the edges of the tensioning hoop. A 10" or 10.5 straight edge for an 11" rim, a properly tightened head will sag at the bridge about the width of a US Quarter. You can use a common open end wrench to tighten the nuts on the J hooks. Do this a 1/4 a turn evenly all around and repeat until the head tension is as desired. You can feel the amount of force needed to turn the nuts and which ones are harder to turn. You do not want to over tighten the nuts but they do need to be approxible the same tension. This will brighten your banjo and help with to much sustain. I use a thick boot sock also as suggested in previous post.

[Jess L.]

... metallic, grinding sustain... I can induce the ring just by tapping on the skin without touching the strings, though not when I lightly damp all 4 strings at once. ...The strings are a decade old but haven't actually been played much.

(bold above added for clarity)

I think the key here is that you said the problem goes away when you "lightly damp all 4 strings at once". To me anyway that points suspicion to something with the strings or neck or headstock, so I would suspect one of the following:

1. A loose winding on one of the strings. Or:
   
   
2. Open string(s) contacting fret(s) if the action is too low or if there is a rogue fret that's too high.

You said the tenor banjo's strings were a decade old.

The loose-winding scenario is plausible even if the strings haven't been played.

10-year-old strings can corrode just from moisture in the air and develop weird problems such as metallic sounds and buzzes on the wound strings, and other more subtle problems such as intonation issues etc.

I had a loose winding on a fiddle string once, although that was an instrument that got played quite a bit, but it took me a while to track down where that horrible new buzzing sound was coming from. (I was still new at fiddle, so unpleasant sounds were part of my everyday practice experience at the time.)

I'm stuck for a few days in a place with only an old no name tenor banjo to play...

If you're able to get out to a music store to procure a new set of strings to put on, that would be the first thing I'd try.

If I didn't have tenor banjo strings handy, if there were any spare guitar strings laying around, I would be tempted to (temporarily) cobble together a set made from guitar strings of similar gauges, just to experiment with.

If the problem goes away after you change the strings, cool.

However, if that doesn't solve the problem, and if the strings aren't too low and contacting the frets unexpectedly... then... hmm, what else could it be... guessing, maybe something loose in one of the tuners on the headstock? Or something loose or weird about the nut or nut slots?

But I'd change strings first (if you have access to new strings, although if you're in a mountain cabin or something that might not be an option), and see if that helps, then proceed from there.

Edited to add:
It just occurred to me that there could be another possibility as well, that the problem could still be something in the rim *if* the undamped open strings are somehow inducing sympathetic resonance with some loose part in/on the rim... guess it might be more complicated than I'd first thought... What happens when you slightly change all the strings' pitch just a small amount? I'd experiment with that as well, tune the strings up or down just a little bit, not necessarily even a whole fret, see if the unwanted sound is still there. And as already mentioned by other posters, if you can get ahold of a Crescent wrench to adjust the head tension, that would be another thing to try, because the head might happen to be tuned to some note (banjo heads are tuneable just like strings are) that causes excessive vibration at a certain frequency that might make other stuff vibrate in undesirable ways. I wish I had that banjo to experiment with, it's got my curiosity.

[s1m0n]

Thank you. The action is far from low, and the noise is certainly coming from the pot end, not the headstock. I can hear that much. I'll try the strings and the head next week when I'm back to civilization, but for now the sock cure is making enough difference to make it playable, although the sound isn't optimal.

Your theory about the strings is a good one, because the problem seems much less apparent when I mute all the wound strings and leave the E string open.

[s1m0n]

Well I'm out of reach of new strings, but not of an egg-beater drill & a set of bits. I took the resonator off the back and started looking at what I could do to fix the action. It turned out that the action was determined by the position of the stick relative to the far end of the far the pot which is screwed to the tailpiece-end of the pot. I looked, and realized that two holes meant that the position has been adjusted at least once, and given that the action was ridiculously high, I decided that it might not hurt to add a third stick landing, about the same distance from the first, and hope that the ensuing lower action isn't too low.

Which it isn't. This banjo went from "absurd" to, "upper end of playable; no chance of fret-buzz noise".