Posted by Rick Denney on April 19, 2002 at 15:38:59:
In Reply to: Re: Re: Re: Re: Re: An interesting tuba on auction site posted by Klaus on April 19, 2002 at 15:24:46:
I think it is a terminology issue. Yes, it functions as a double tuba. But the airpath is always going through all seven valves--at least that is my clear impression from the photos. In my own concept of a double tuba, the airpath goes through the other half of stacked valves only when the switch valve is brought into play. It is a distinction that doesn't affect how the buttons work, but it seems to me likely to feel the effects of going through seven sets of rotary-valve ports even when played as an open F.
The true double F/BBb made by York and pictured in Stauffer has ganged switch valves upstream and downstream of the valve body. In the F position of the switch valves, only the valves' F ports are used, and in the Bb position of the switch valves, only the valves' Bb ports are used (plus an addition length between the valves and the downstream switch valve. Thus, the air path goes through only one set of valve ports.
Rick "trying to make a distinction between these two approaches to double tubas" Denney