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@bloke serious question, have you ever seen any rotor witness marks put on by a factory that are actually off? in other words, from the factory, the rotor is marked for misalignment? I've got to think that is rare but not unheard of.bloke wrote: Thu Jan 08, 2026 9:24 pm Here are the "have you checked to see if it's plugged into the wall?" questions:
- rotor alignment?
- rotor leakage (often caused by a "repair tech") ?
- leaky solder joint or rot hole(s) somewhere in the circuit?
plenty.tubatodd wrote: Fri Jan 09, 2026 10:48 am@bloke serious question, have you ever seen any rotor witness marks put on by a factory that are actually off? in other words, from the factory, the rotor is marked for misalignment? I've got to think that is rare but not unheard of.bloke wrote: Thu Jan 08, 2026 9:24 pm Here are the "have you checked to see if it's plugged into the wall?" questions:
- rotor alignment?
- rotor leakage (often caused by a "repair tech") ?
- leaky solder joint or rot hole(s) somewhere in the circuit?
I have not checked any of this things, all I did was clean it the best I could. Thanks for the advice, it is much appreciated.tubatodd wrote: Fri Jan 09, 2026 10:48 am@bloke serious question, have you ever seen any rotor witness marks put on by a factory that are actually off? in other words, from the factory, the rotor is marked for misalignment? I've got to think that is rare but not unheard of.bloke wrote: Thu Jan 08, 2026 9:24 pm Here are the "have you checked to see if it's plugged into the wall?" questions:
- rotor alignment?
- rotor leakage (often caused by a "repair tech") ?
- leaky solder joint or rot hole(s) somewhere in the circuit?
So did you only change the rotor or the casihg as well?BramJ wrote: Fri Jan 09, 2026 10:58 am My Amati 6/4 has an aftermarket 4th valve. It is an "open wrap" and not stuffy at all.
Thanks for the answer I will check for missaligment.the elephant wrote: Fri Jan 09, 2026 10:55 am I have seen several Cerveny and B&S stencil instruments where they were carelessly struck, so that the die bounced, leaving two marks nearly overlapping and giving a "blurry" look to one of the two marks.
I believe there is too much ressistance, the problem is indeed with 4th valve low F and lower. When you play the 4th valve it just does not want to take air. Now at first I believed that I just have bad technique. But I had my ex professor, who is a very good and succesful tuba player with different orchestras, to try it and he came to the same conclusion. Now I do not see how sleeving would help, but I guess sometimes the opposite of what looks logical could work. Since I have no knowlege of the tuba design/build you answer seems very interesting. Thanks for your replyarpthark wrote: Fri Jan 09, 2026 11:01 am Random thoughts/observations that may or may not be applicable to your situation (if the rotor is properly aligned and all the stuff bloke said above):
"stuffy" is a subjective term.
Sometimes, the problem isn't too much resistance, but not enough resistance. I think of the big York style 6/4 CC tubas, one of which I own and two of which I played recently (a demo model Eastman 836 and a very well preserved Hirsbrunner HB-50). The bore size on the fourth valves and the fifth valves on these tubas is quite large, but the low range can be, for want of a better term, "stuffy." I don't think valve bore size has a lot to do with it and the problems are elsewhere in the instrument, which is overall a very large horn.
Last thing. The low C on German style F tubas can be finicky. Your big Cerveny Kaiser is essentially a blown-up F tuba (in proportion/wrap), and those issues can still persist with your big BBb's equivalent low fourth-valve F. Some folks have had some success by "sleeving" the inner bore of the fourth valve tubing, making it smaller and introducing a bit of resistance into that circuit.
Edit to add that the Cerveny/Amati/Lignatone 6/4 kaiser bore is 21.2mm (.834"). That is already very large, and I don't think you'll easily find a meaningfully larger rotor.
It was done before I bought the tuba, so I don't know the details, but the bore of the 4th valve is the same as the othersTubadbadu wrote: Sun Jan 11, 2026 3:12 pmSo did you only change the rotor or the casihg as well?BramJ wrote: Fri Jan 09, 2026 10:58 am My Amati 6/4 has an aftermarket 4th valve. It is an "open wrap" and not stuffy at all.
Also where did you buy an aftermarket rotor? I can't seem to find it on the internet. I will first check for any leaks/missaligments, but if that does not work I would try to change the rotor. Thanks for the reply