Posted by Klaus on April 08, 2001 at 10:57:21:
In Reply to: Conversion of F tubas to Eb posted by Jay Bertolet on April 08, 2001 at 10:13:36:
Adding cylindrical tubing to tubing, that ideally should conical all the way, is not without its problems acoustically. The technical side however is fairly easy, if one can get deliverance of tubing of the rigth diameter and wall strength.
I have used externders for bassbone 2nd valves, which is fairly unproblematic in sound.
To compensate for "sharpening-by-mute" I also have used extending of the main tuning slide of an Eb bass.
On the YFB621 you might only need extenders on the main tubing slide. And maybe on the 4th valve. Authorised Yamaha repairers should be able to get the original tubing for you.
To secure the positions of the pulled valve slides 1 through 3 (or 4) you could find hard plastic tubing, that could be cut in the extending length and be put on one of the male branches of each slide. That should prevent accidental push-in’s of the slides.
This method might appear low cost and low abitious, but it might give you a fair test of the very idea of extending from F to Eb.
Klaus