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As the sousaphone's valve section is unsuitable for your purposes and you don't seem too attached to it anyway, sell it to someone who wants one, and use the money to procure a valve section that will work?

I completed a similar project myself several months ago. But I had thought about it for many months before knowing it would work! I took the 4v cluster from my King Eb raincatcher and soldered it my old "extra" Holton Monster Eb I had laying around. The King Eb raincatcher was very out-of-tune with itself, and wasn't being played; but had a great valveset. The Holton Eb was only a 3-valver, but it played in-tune with itself and made a nice sound. The Holton Eb valve bore is around .660", and the King .687" wasn't much bigger, so it worked very well. There was LOTS of re-adjusting & cutting, though, to make it work. I also soldered-on a Yamaha leadpipe. I call it my "FrankenHolton". I've used it on quite a few rehearsals/gigs over the months. The Yammy leadpipe and .687" valveset give it a little more "horsepower" than before. Had to cut the leadpipe and main tuning slide a little to bring it up to A-440. I designed it to use a mpc adapter or sousa bit, and it works very well. It's a very funky-looking tuba, though

There is a big difference between a .687" valveset and a .812" valveset. I'd leave the King Jumbo alone, especially if it plays well. Obviously, the easiest route would be to track down a 4v cluster from an old crapped-out 1241 or 2341 for your King Monster project. But if you want a bigger valveset bore (for more "horsepower"), maybe go up to a .729"-ish valveset from an old crapped Selmer or Yammy sousa? I honestly think if you go much bigger than that, you will encounter intonation/response issues on your King due to major/immediate changes of inside bore pipes
Or, like you said, go the Oberloh route.

KiltieTuba wrote:Uh... No. The King .812 is staying with me until I die or suffer a serious back injury that would prevent me from marching with it.

But you would harvest a valve set from it?

Why have a valve set for each tuba, when you can only play one tuba at a time? Just swap the one valve set into whatever tuba you want to play, remembering of course to leave 15 or 20 minutes time for this task before you take off for your gig. Naturally the largest bore valves.

Ian, .812 is such an unusually large size bore for a piston tuba - the stroke must be quite long. The largest bore I ever saw in a piston valve was .773 - I used to own a 4 valve 6/4 Conn that was that size.

Do you want this horn to have 4 valves? I'm assuming the .812 set you have is also 4 valves.....

If so, you might be better served if you look for an old Yorkmaster (Boehm & Meinl, .748 bore), or, occasionally I see Conn 4 valve E flat sousaphones with .734 bore, up for sale.

I think the offset style valve cluster would work better than the "in-line" Holton - Meinl Weston variety, especially on a sousaphone.

.734 or .748 would be a closer compromise to .812 than would .687.

Good grief, those stems are looonnggg!

From the looks of it, that piston needs to be pushed down 3 seconds before you play the note...

KiltieTuba wrote:It's reassuring that people have some of the same ideas that I do and I'm not just going crazy!

Don't count me, I was only joking! Taking that valve section out is the best way to make sure you will never play that sousaphone again. I am no tuba designer, but my intuition is that the best valves for that King Monster will be very close to its .687 bore, and as toobagrowl suggests the natural solution is valves from a 2341 or whatever. Aren't they identical, in orientation, to the King sousaphone, minus the 4th valve?

I tend to agree with Donn. There might be a reason why King tubas with a .750 bore (or .812, for that matter) are so rare.

Besides (not intending to open a can of worms), there's been a fair amount of speculation out there that larger horns *may* benefit from smaller bore valvesets, such as the Martin.

I could certainly be wrong, but I think the King sousaphone 4 piston valvesets were oriented differently than their "concert" tuba varieties.

roweenie wrote:I could certainly be wrong, but I think the King sousaphone 4 piston valvesets were oriented differently than their "concert" tuba varieties.

OK, I see this is true also of the 3 valve sousaphones. I get along OK with the 1240 valve setup, bell straight up. Though it did cross my mind recently that lighter valve springs might be in order.