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This is my spanking new 21J conversion. It's a frankenhorn made from the body of a 20j, a valveset from a 2xK sousaphone, a new fitted lead pipe, and some new inner and outer slide tubes.
The process was this: Find a 20j clunker, torch it apart, find a suitable valveset, de-dent all the body parts, tack the body together, think a LOT, lap the valves a couple times, turn tubes around to slide the set into place, solder it in place, brace the hell out of it, attach the lead-pipe and receive, lap the valves again (1&3), stick a borrowed bell on it and honk.

here is the first picture of this honey, more to come later

I played some open notes and everything lined up great (there's still lapping compound in the valves, I finished this morning). The low Eb is still there!!! I was extremely excited about that, I am going to see later today how she sounds chromatically when I clean it out.

Rockin!

The Bb below the staff and in the staff are the worst notes (believe it or not ) Every other note is manageable and within reasonable tolerance (for my tastes). By worst I mean 20cents sharp pulled out a majority of the way. I was able to correct the problem with lipping and pulling, not too hard if practiced continually. It has a great warm sound and is gigantic! I am going to try to find a big concert hall when I get home to test this thing out.
Compared to a Miraphone 1291CC:

What would you say the TOTAL cost of this project was? (other than the price of the 21J itself). I have a 20J and am still interested in buying another one and having this done. It would be great if you could type up a STEP BY STEP procedure of this process for other people to use as guidelines. It would make things much easier for us! Thats a cool lookin horn though! Congratulations

to tubajohn
I wouldn't do this with 20j valvesets if that's what you intend.
find your beater 20j and find a crappy fiberglass sousaphone, short action if preferable.
I used the main slide from the 20j and made a collar to fit the small leg to the exit port from the valve set.
Buy a new leadpipe tube and bend it to fit, save the reciever and brace from the 20j.
Flip all the bows (goes without saying)
clean the joints and solder the body in place except the last couple sections, this will help when fitting the valveset.
set in the valveset to the best of your ability.
make some joints to keep rigidity
brace the tuba together wherever you see fit.
solder in your custom bent lead pipe clean it up and play it.

Sweet horn: any chance of adding a fourth valve down the road? (not that these beasts need them too much)

Don't know how much it matters to folks but the 20K has a smaller valve section than the 20J tubas.

I have a valve cluster waiting for me at home to convert into a fourth valve

TubaTinker wrote:Don't know how much it matters to folks but the 20K has a smaller valve section than the 20J tubas.

Ah, I figured he took the original 21J valveset and converted it to front action (haven't really been following the conversion process, though I knew he was working on it). The 20K does have a fine valve section. I wonder how this horn plays; it'd be cool to give this beast a toot, but I'm pretty far away. Nice project horn, though; I wonder how it'll compare to a 34J if you get that 4th valve in.

I am pretty confident that this horn will toot with the best of them once pitch is sorted out and the fourth is installed, it got the sound that I wanted out of it. I like it , hopefully a tubenetter will come to Aurora, IL and honk it to give me an honest opinion.

tubatom91 wrote:I am pretty confident that this horn will toot with the best of them once pitch is sorted out and the fourth is installed, it got the sound that I wanted out of it. I like it , hopefully a tubenetter will come to Aurora, IL and honk it to give me an honest opinion.

Well it does look pretty nice for being your first "frankenhorn"; if the pitch is manageable within reasonable tolerance -with just three sousaphone valves- I must tip my hat to you sir. Again, cool looking project!

tubatom91 wrote:.... hopefully a tubenetter will come to Aurora, IL and honk it to give me an honest opinion.

Mammoth2ba is around the corner from you in Michigan and Steve Marcus is there in Chicago. Both have experience with the large front-action Conns. Maybe you could meet up with them for a play test.

k001k47 wrote:

TubaTinker wrote:Don't know how much it matters to folks but the 20K has a smaller valve section than the 20J tubas.

Ah, I figured he took the original 21J valveset and converted it to front action ....

In the original post... the author mentioned that the valve cluster is from a 2XK (sousaphone). Changing a valve cluster from top-action to front-action is a very daunting task... one that I have considered, but not seriously.

Beautiful horn Tom!!!..................................bigbob

Hi there,
I know this post is pretty old but I'm interested in this horn and was hoping you could give an update on its status. Inquiring minds want to know!
Thanks

I'd be interested as well. The next trip to my in-laws after I come into possession of an appropriate four valve set I'm taking my 21J to Dan for such a conversion.

It looks really great!

I noticed that you extended the upper #1 tubes and turned them into a functional slide. That's a great idea.

Since the 20K valve set has a smaller bore, does it play noticeably different than the 2XJ's?

Well, I will try to post a picture tomorrow, you're lucky and caught while I have both horns in the same city . The Conn is slightly smaller than the Holton overall, although the bell size is larger. The bore size difference is less noticeable than one might think. The tone of both the Conn and the Holton is pretty similar and would easily blend played next to one another. I know if I had an upright bell for my Conn I would enjoy playing it a hell of a lot more than I do now. pics to come tomorrow.

Make a youtube comparison!
How's the intonation?