Posted by Eric on December 21, 2003 at 16:26:49:
I just realized my Besson 1918 Eb tuba uses a different compensating valve system than my 1970's Besson baritone.
On the baritone the setup is like a standard 3 valve system, except that the third valve slide loops up to the top of the first valve where the sound can go through additional loops of tubing for each of the first two valves pressed, then back down to the third valve and into the bugle.
The tuba is designed differently. On it the leadpipe feeds into the top section of the third valve and when no valves are pressed loops back to the bottom section onthe first valve slide and progresses normally through the valves into the bugle. If the third valve is pressed, the sound goes though the top section of each of the first two valves, each of which having a completely seperate and longer tuning slide. From the first valve the sound goes though a length of tubing equivalent to a third valve slide, then back into the third valve and onward into the bugle.
A full double french horn has seperate tuning slides for both pitches, whereas a compensating double feeds the sound through each valve twice to add the additional tubing for the lower key. The baritone is akin to a compensating single, so what is the tuba? Is it a half-double, a full single, semi-double or do both systems have the same name?
What system is used on current production compensating instruments?