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What do you do about a tuba that is frequently flat with the main slide all the way in? . . Cerveny 686-5R.

How flat is it? when you first start playing? ... or after a reasonable warm-up period?

Have someone else play the horn and see if the results are the same.

Check for leaks.

Check rotor rotor alignment.

Report back.

sailn2ba wrote:What do you do about a tuba that is frequently flat with the main slide all the way in? . . Cerveny 686-5R.

Go adjust the thermostat. That should help.
I can't remember if hot or cold helps you go sharp...

On a more serious note: Check for an old sock in the bell. Adding an impediment to the air stream makes your horn play flat. Want a more pronounced effect - add a small pillow, that makes you really flat. Any smaller impediment (like from misaligned valves) gets into having a tech check the horn instead of doing it yourself.

Have the horn thoroughly checked before you have any "cuts" made. Like the above posts say take it to a good tech before hand. One that also is a tuba or brass player usually helps.

Some tubas are sensitive to some constellations of playing style and mouthpiece.

First, get a Kelly plastic mouthpiece and file down the shank so it goes farther into the receiver. If that's not enough (and all other things mentioned above have been checked) then get out a fine-toothed hacksaw and take an inch or more off the main tuning slide. If you do it carefully and use a file to trim the cut ends it is possible to make the repair look good as new. (First put duck tape over any areas that might be hit or scratched in the process.) If you have never tried such operations before it's a good idea to practice on a junk horn first.

The 183 I recently purchased had corrosion in the receiver/leadpipe joint, and the wrong "gap," resulting in inconsistent intonation and generally flat pitch, getting worse when ascending in register, so that the upper octaves were almost major 7ths. A cleaned up leadpipe and new receiver installed with the correct "gap," and the horn now again plays well in tune.

If the horn plays consistent in scale from octave to octave and interval to interval, then yes, there may be something in the horn, there may be another leak somewhere, or it could just be a flat horn that needs shortening of tubing somewhere.

TubaTinker wrote:How flat is it? ...
Report back.

bloke wrote:Isn't there another regulating variable (how's that for juxtaposing two words with somewhat opposing meanings) ?

- Organ pipes will have room-temperature air blown through them, and will continue to sit in room temperature air.

- Tubas will have 98° F. air blown into the small ends of them, and tubas will be snugged up next to a mass that is generating 98° F. from its core.

In theory, The air in the majority of a tuba (or sousaphone) will remain at 'room' temp. Only a small portion of the tuba is heated by the player.
There may be 98°F air entering the tuba, but the tuba (being made of brass) is like a heat sink. It will reject most of that heat back to the air around the instrument. Even with a fiberglass sousa, the brass section is more than enough that it should be at room temp by the time that the air inside reaches the fiberglass section.
Also, your body isn't radiating heat at 98°F. More like ~70°F at the skin level, Potentially MUCH cooler at the finger tips too. Any clothing will prevent that radiating heat from reaching the instrument. Your surface temp (at the surface of your clothing) is very close to room temp if you're wearing more than 1 layer of clothing.

I've got access to a thermal camera. I think I'll try and take a look at this with the guys in the community band and report back here. That may take a week or 2 to get the permissions on the camera from the guys at my office.

I've often wondered what effect this has on instrument production.
Will, for example, a Kanstul tuba made in sunny California be constantly out of tune in Alaska?