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I have an Eastman 864 F tuba (great tuba, by the way), but the 3rd slide is too long.... 5th position (2+3) is always flat

Sousaswag wrote: Fri Jun 26, 2026 2:30 pm That’s not unusual for many makes. On their rotor F tubas? I haven’t experienced that.

You say 5th position… Are you a recovering trombone player? Practice with tuning drones in your ear with long tones. See if the pitch comes up.

bloke wrote: Fri Jun 26, 2026 3:18 pm

I have an Eastman 864 F tuba (great tuba, by the way), but the 3rd slide is too long.... 5th position (2+3) is always flat

I'll take your word for this...

Typically (with many conical brass instruments) the 2-3 combination (just as with 5th position on a trombone) is severely sharp for some pitches and severely flat for others. I'm pretty sure this is because there's a tremendous amount of cylindrical tubing involved (distorting the taper) YET it's used for FOUR pitches - rather than only two, such as with 6th and seventh position (or 4th valve and 2&4 valves).

Typically (valve combination 2-3 with F tuba) 2nd partial C# (just below the staff - F tuba) tends sharp, 3rd partial (G# at the bottom of the staff - F tuba) tends slightly sharp, and C# (middle of the staff - F tuba) tends flat. whereas the top C# (just above the staff (also tends flat.

BUT THESE CAN ALL VARY ON VARIOUS MODELS OF F, E-flat, C, and B-flat TUBAS (as their body tapers all vary from each other so drastically)...

but (in general, being less specific about particular partials' tuning characteristics) 2-3 is "squirrely" (again, just as is 5th position on the trombone).

Eastman rotor tubas are (sort of, though some config and taper differences) copies of early B&S F tubas.
With my (6-valve) B&S F tuba, I LOWER the pitch of the C# below the staff by playing it with 1-2-6, whereby I can tune the #3 slide to FAVOR the two flat-tendency pitches played with 2-3. G# (as far a so-called "slot") is so barn-door wide, that I can put it anywhere (as long as I'm paying attention - and I believe I generally do).

bloke wrote: Fri Jun 26, 2026 3:23 pm good...but - based on experience - I wouldn't (if doing a build) just start measuring and cutting - fully relying on that chart.

bloke wrote: Fri Jun 26, 2026 4:15 pm top C# (above the staff) usually works quite well (security and pitch) with 2-4 if 2-3 is flat for that particular pitch.

I know others who've shortened that circuit.

If yours is a rotary B&S copy, I'd recommend (if shortening is decided upon) shortening the circuit tubes which lead up to the slide, and not shortening the slide tubes themselves. (remove the #3 slide assembly, shorten the tubes, reinstall the assembly...It's actually LESS work).

RoseCityInstruments wrote: Fri Jun 26, 2026 3:19 pm
F Tuba 12 ft. open pipe

F
1st valve = 18"
2nd valve = 8"
3rd valve = 27"
4th valve = 48"