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I got a good deal last year on a used Dynasty M890 four-valve BBb sousaphone. It's been nice to not have to hold my concert horn on those occasions when I'm asked to stand and play. The horn looks good and has a smooth sound.

The only issue I have with the horn is that the fourth-valve plays extremely flat. When trying to play a C below the staff it sounds closer to a B. It's so pronounced, that I've searched Tubenet and Google to see if some fourth valves are designed to play that low. I haven't found that information, so I'm left still wondering whether or not it's meant to be that flat or if it's a flaw in the horn.

In the meantime, I use 1&3 instead of 4 and I feel silly carrying around a horn with a valve that I don't use.

Do any of you have any experience with this horn or have any leads on what's going on here?

Thanks.

Thanks, Bloke. That's the conclusion that I was coming to as well.
Now I just need to find the time to practice the new fingering combinations!

bloke wrote:It seems to me that you might either have the 4th valve loop shortened, or (as you are doing) use 1-3 for C/F, use 2-4 for B/E, and use 1-4 for Eb...eh...??

Could he likely do both? I tune 4 flat, on my 40K, but not that flat. It doesn't need to support combinations like 1-34. I'd want to be pretty sure I was solving the right problem before an irreversible operation like that - for example it would be a shame to shorten a valve because it's got a leak that makes it flat - but it seems like something that would be easy to do.