Posted by James W on June 23, 2000 at 08:08:33:
In Reply to: Re: Questions posted by Rick Denney on June 22, 2000 at 13:36:04:
Another reason for venting valves (or, as you say venting the tubing) is that when you release a valve whilst blowing, the air trapped in the valve tubing will be at a higher pressure than the air around it. If this is released when not blowing then you get the same popping effect as you would by moving slides with the valve released and then pressing it. I don't know how audiable this is with a tuba (I have only ever really played piston valve horns), but on trombones it is loud enough to have made Conn produce their CL2000 valve with the ports aligned so that the opening into the slide is opened before the opening to the bell, so that the "pop" of air is directed into the slide and not amplified by the bell.
James.