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Edit:

This thread is me tracking what the heck is making my Yamaha 621 F clone buzz on pitches that involve the first and second valves.

Since it follows the piston,

Is there anything that is possibly slightly loose on the piston?

Stem, valve guide, button, etc?

If you put light sideways pressure on the button while playing, does it still buzz?

I tend to doubt that's the cause of the buzz.

I would look towards a #3 top valve cap ("cap", NOT "button") which FEELS tight, but - when you actually "CRANK" it - the buzz finally stops.

Depressing the piston puts pressure on the top valve cap, which also causes the buzz to stop.

Hasn't the valve cap threading already been criticized ?

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I could easily be wrong...

another thought,

if the bottom of the piston isn't flat where it touches the valve spring, I suppose the spring could become somewhat undamped. Ie, the circle of the spring might only touch on one side of the bottom of the valve and therefore the spring gets unintentionally canted. It might then buzz in the up valve position, but not when the spring is compressed by the down position.

Thanks for your input, sincerely. Will read over these responses later this afternoon. Feel free to keep theories coming.

I believe that pistons are actually hollow. There could be something inside it?

What exactly is the "weird buzz" like?

If it's the porting thing, that would affect response and if it was extreme enough (sounds like not) some kind of flutter?

I think the port issue is something you might find throughout the tuba, rough edges that should/could be straightened out during manufacturing to make everything fit as cleanly as possible. It's an easy step to say "good enough" and solder it, or to pick at it until it's perfect, then do a little more, then solder it.

If it's truly a buzz, that says to me "metal on metal"
* Check the valve springs... Better yet, order some Yamaha springs that are plastic coated, those things are silent.
* Do t just check the 3rd valve spring, sometimes the resonance of the horn makes the other springs vibrate too. Cheapo and worn out springs are the loudest.
* Check to make sure there's no loose or broken solder joints. They can be weird and only be noticeable on certain notes. Given Chinese tuba QC experiences shared in the past by others, make sure that every brace and connection point is actually soldered, and nothing was forgotten. I would check them all, including the bell to top bow connection point.
* Check the bell rim... Anything funky there?
* Any chance the knuckle on the valve block isn't fully soldered? You'd notice an air leak too... But that's more metal on metal that to check.
* No loose screws on water keys, lyre holder, or anywhere else (not sure if you have detachable leadpipe or whatever).
* No loose rotor linkage/other parts that rattle at that resonant frequency?

I'm doubting it's the port, but I could be wrong!

Oh, and also, maybe just flush it out just in case. Something might be lodged in the horn?

I also doubt a burr in the piston would cause a buzz... You'd probably notice it on the valve action. My bet is also on the spring(s) or a solder joint that's broken or just barely not soldered enough.

Yamaha springs are something I have put into all my piston tubas, regardless of make/model. The plastic coating does indeed make them silent, but as usual make sure they're seated correctly. If they're off center they will buzz. They're like $20 on Amazon for a set of four.

One other thing it could be- shake the tuba with the springs out and listen for debris moving around? It IS a cheap clone after all. There could be "stuff" lodged inside some hard-to-empty tubas.

If you find that the buzz completely stops when you really crank on the threads of that top cap, you can take a plastic or rawhide mallet that's not large and tap fairly smartly around the sides of that cap and then tightening it and loosening it after a set of smart taps. Eventually, the soft brass threads will cut in hard all the way to the very end, and you'll be able to tighten that cap properly without the buzz and without having to crank hard on it.

All of this assumes that it is the top cap, but that is a common culprit, based on how far you've chased down the source.

I did a lot of messing with the valve caps and such and didn't have any results. I also took off all the valve caps, and the ring/resonance thing I am getting is still there, so I don't think that's the issue.

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Part 2 (edited):

If it's happening with all those different situations you may have a solder joint that's loose. The last thing to try before finding the loose solder joint is probably to take all the springs out and see if it still makes those noises.

bloke wrote: ↑Tue Apr 25, 2023 9:59 pm If it's happening with all those different situations you may have a solder joint that's loose. The last thing to try before finding the loose solder joint is probably to take all the springs out and see if it still makes those noises.

I messed around with it for about an hour and a half out in the barn chasing all possible avenues. I took out the springs, yeah, still happening.

I actually do think it's a loose solder joint, but would this go away if the solder joint were grabbed/held fast? I can't find where it is.

I have an appointment with a repair guy, so we'll see if we can chase this issue down.

Thanks all for your help and for listening to that goofy video.

Messing around with it last night for so long, I made those videos but didn't really offer a report:

Although the buzzing problem occasionally goes away with D and A when playing those pitches 3 instead of 1-2, the buzzing issue is still present when playing notes 1-2-3 (which I hadn't really experimented with before), so I don't think the issue is in the 3rd valve porting, as many of you correctly guessed.

I was able to track it down a bit more by taking out the fourth valve slide and pressing down different valve combinations to see where I was getting the buzz. I think it's in the first valve circuit, because that telltale buzzy synth sound I was getting, I could hear come out of the open fourth valve slide when depressing 1. It seems to be near the spring bar for the fifth valve lever that is soldered there. I am guessing a loose solder joint or something.

I have an appointment with Dick Hansen up in MA, who a lot of the Coast Guard Band guys take their tubas to, so hopefully he will be able to help me track it down and offer a solution.

I think you'll find a loose solder joint more likely by pulling and tugging on tubes, rather than depressing valves, since you've eliminated valve caps.

I depress valves by telling them their sole purpose in life is to be manipulated.

Took it to a repair guy today and he couldn't figure it out. Solder joints seem fine.

I'll do some more stuff to try to isolate it. It's definitely somewhere between the mouthpiece and the fourth valve tubing section, because removing the fourth valve slide and depressing 1-2 also makes the buzz. Piston porting was fine. Alignment was great.

He said that it is not noticeable to anybody but the performer, but it's still irking me.

Drawing board...

The pitches you're playing sound to me as if they're "in the cracks"...maybe (??) somewhere in nebulous-land between D and E-flat.

Was I seeing you mash two buttons? (me: old / phone screen: small)

I wonder - if it's a sympathetic vibration, and if you lower the pitches down to pitches that are useful - if your buzz will still occur (??)

Of course, I too would prefer that my tubas not sympathetically vibrate with any played pitches - whether they're useful pitches or not.

bloke "If you brought it to me, I - too - could fail to find the cause."

Yeah, I was playing with all the slides all the way in, while diagnosing.

Still occurs at A=440... I did check that with the tuba properly tuned. Good thought though!

God bless my repair guy. I was there for four hours. Had quite a bit of work done on other stuff, but this was the stumper.

Taking out the first valve slide and playing through it, the buzzing still happens. Swapping the 1st and 3rd pistons and taking out the third valve slide and playing through it, it still has that buzz, so I think it might (???) be something in the first piston that is sympathetically vibrating. I shake it and hear nothing. However, the valve stem is really cranked on tight and I can't get it loose. I wonder if that's related.

I have some other folks I am considering taking it to, but will keep trying my primitive home diagnosing for the time being.

In the meantime, I have a really excellent Besson Eb for my bass tuba needs, so this isn't a pressing/urgent deal. Just kind of annoying, because I am ready to really like this tuba.