Intonation Problem Identified

[Rick Denney]

It wasn't all those chill pills I've been taking. And it wasn't low F training on the F tuba. Nor was it any excuse for me to feel particularly good about my progress (or bad, for that matter).

You will recall that several weeks ago I started a thread asking for advice about my inability to play a Bb tuning note up to pitch on the Holton. I reported that I was 20 cents flat when tuning with the band at the start of rehearsal, using the oboist's reading of a tuner as a reference, but that it never seemed to be a problem later in the rehearsal. When the instrument was behaving this way, there was nothing I could do to pull it up. But sometimes, I would pick up the horn and it would play fine. Inexplicably right on the mark. Was I going crazy? Was my tuner battery going dead? Is my pitch sense even worse than I thought? Should the oboe player, who was looking at the needle during the tuning note at rehearsal, be shot at dawn? Should I sell my F tuba because it was ruining my embouchure? Should I retrain myself to play everything such that it feels sharp? Should I chop an inch off an already short main tuning slide with the nearest handy hacksaw?

Well, no.

I stumbled upon the answer this evening. I picked up the instrument (after, shall we say, several days of sitting in the case), and found that it didn't sound right. I was just blowing a few notes, chops cold, just to get the air going, and the first notes rarely sound right so I didn't really think about it. The horn was at room temperature and not particularly cold. But I turned on the tuner, and, sure enough, I was 20-30 cents flat across the scale.

Then, I oiled the valves. (Bloke will know where this is going, and he won't be the only one.)

On the next note, the needle was dead center. And on every other note after that. Right where I pointed it. The only remaining trouble note was the original difficulty with a sharp sixth partial (and this tuba is in good company with that problem).

Here's the post-mortem: The tubas sit in the car all day on rehearsal day. I spend 45 minutes or so in quintet rehearsal on the F, and then we break before the band rehearsal. I put away the F, pull out the Holton, blow one or two notes on it, and set it down for fear of destroying what few chops I have left at that point. I'm already warmed up, right? The next note I play is the tuning note. Then, the conductor often gives us the rehearsal order for the evening, and that's when I remember that I haven't oiled my valves. They are dry after sitting in the car (and for other reasons that we won't go into).

Note to self: Oil the valves before the first note. I should do that anyway, but now I have new motivation to remember. And it probably also means that I have a valve job in my future, though when oiled all is well.

Rick "glad he kept the hacksaw at bay or dispense with the oboist" Denney

[Mark]

I stumbled upon the answer this evening.

So those of us who encouraged you to have another player test the tuba were right. This is a quick method of determining if you should focus your investigation on the tuba or the player.

However, if you had oiled your valves before handing the tuba off to some one else, that really would have driven you nuts.

[Kevin Hendrick]

... when oiled all is well.

"Oil's well that ends well", eh? Glad you found the problem.

[Doug@GT]

How do dry valves affect tuning like this?

Doug "ignorant"

[Joe Baker]

That giant sucking sound is a LEAK. The oil just seals it up.

_____________________________________
Joe Baker, who was going to suggest Rick put it in the dryer and shrink it....

[tubeast]

I always thought valve oil in the tiny gap between valve and casing hardly was subject to evaporation, no matter what it consisted of, because of consealment from air.
I always figured the greater need for lubrication origined from the fact that the axial motion of the pistons leads to a greater amount of oil to be squeezed out of that gap. (Like if you take a handfull of sand and rub your hands, at the end of each stroke grains of sand will escape from your palms)

Well, luckily we keep learning something new each day.

[MikeMason]

my best guess: old valves with a bit too much play are somewhat sealed back up with oil. ie hetman's "classic" piston oil. a little higher viscosity for just this purpose... a loss of compression for any reason will affect intonation...

[Dan Schultz]

All of this seems pretty elementary. I always thought the main cause of intonation problems (other than my sometimes crummy chops) was leaks... including worn pistons, poor piston alignment, missing waterkey corks, loose slides, and just holes in general.

[windshieldbug]

My guess is that because the valves are loose, they allow the oil to go down to the "one molecule" (or whatever) level. Then the internal wave setup in the tube finds those "gaps", and reacts accordingly. I suspect that is why when only partly dry, only certain notes are "affected", finding new node points just slightly away from the usual. Oiling fills the gaps, the waves return to normal, and act the way they're supposed to.

Or not. Maybe your horn is haunted, and the spirits don't like to be left alone, with no human attention!

[Rick Denney]

How do dry valves affect tuning like this?

Doug "ignorant"

The others are right. It's leakage.

And when a tuba sits in a warm car, or over a period of several days, the valves will get dry, or at least dry enough to allow some leakage. Leakage is like not quite closing the tone hole of a flute all the way--don't we teach flute players to make sure they close the tone holes completely? It changes the resonance of the instrument. The valves don't have to be dry, the moisture just has to fall away from the gap enough so that surface tension and capillary action is no longer enough to keep the gap filled.

I've been using Hetman's Classic Piston oil, and have always been happy with the result in terms of valve action. And when freshly applied, it does seal the valves well enough. But it still means the gap is on the large side.

Rick "who takes care of his valves but whose Holton has obviously not benefitted from such care throughout its history" Denney

[Rick Denney]

All of this seems pretty elementary. I always thought the main cause of intonation problems (other than my sometimes crummy chops) was leaks... including worn pistons, poor piston alignment, missing waterkey corks, loose slides, and just holes in general.

It seems obvious in hindsight. But I don't recall seeing any mention of it in the previous thread, heh, heh.

Rick "who eliminated all other leakage possibilities with good service and careful inspection when the Holton was first bought" Denney

[ThomasDodd]

I always thought valve oil in the tiny gap between valve and casing hardly was subject to evaporation, no matter what it consisted of, because of consealment from air.

First it is exposed, through the vent hole in the botton and top cap.

All oils evaporate. The thin ones just do it faster. If you put a drop of 40W engine oil on a plate and let it sit, it will eventualy dry out, first becoming a thick sludge. Do the same with a drop of penetration oil, like WD40 or Liquid Wrench.

Some valve oils have aditives to slow their evaporation, and non-petrolium oils can be slower (like silicon based oil), but the still evaporate. That's why a horn that has sat for a while will have dry valves. My trombone sat in it's case for a few years, untouched. The slide was dry when I took it out. No oil on the inner or outer slide any more.

[MaryAnn]

Fascinating. And I will be more fastidious about oiling my instruments from now on. Maybe I'll become a wondrous player overnight!

MA