Influence of shortening back bow on a specific note

[willako]

Hello,
I have a question about the infuence of shortening the back bow on the quality of a specific note. I have a B & H 1976 4-valve e flat tuba, on which I had the back bow shortened a small amount according to what is called the "Fletcher cut" so that the instrument does not play flat (with a modern mouthpiece). Since then, the F just below the bass clef staff has been very fuzzy and does not resonate well. The tubing that was shortened was straight and many people have done it. Could it affect the sound badly, or is there some other reason for that particular note sounding bad? I never noticed it before I had the cut. I have read that any change in the taper can affect specific notes but this is not a change in the taper, although the straight tubing is shortened. Thanks for any suggestions. William

[iiipopes]

It sounds more like either the solder joint has a glob on the inside of it, or with the cut the nodes/antinodes positions changed and one is on a bracket damping the horn. Any way to conveniently scope the joint inside?

[joh_tuba]

I've played modern German made 4+1 Besson Ebs with the exact same problem. In the case of that horn I think the problem is that the 4th valve slide is too long making the F flat. The owner chose to just learn to lip it up.

Try ignoring intonation and seeking out the center of the resonance and see if the sound improves.

The Fletcher cut may have raised the pitch just enough that your 4th slide is now a smidge too long for the bugle.

[willako]

Thanks a lot for the replies. William