The 38K certainly should be a great instrument. I never had one in my hands, but its de-luxe sibling, the 4 valve 40K certainly points in that direction. And that's the one sitting on its Wenger chair right behind me.
The thousandths-of-an-inch standard measurement of brass instrument bores is an odd entity. Inches are long outdated in the real world, and when used in the portion of the world counting itself the real one (in the Ringling & Barnum sense it actually is right) it creates disasters, when used in out-of-this-world contexts (end of cryptogram).
Even I have been corrupted by using the thousandths-of-an-inch for most of my life. I only know a very few bore standards in mm:
11 mm = older German rotary trumpet (.433)
12 mm = Yamaha French horns (.472)
12.7 mm = jazz trombone (.500)
When I rather late in my life entered the low conical brass world, I was most surprised to learn, that the US type low brasses, at least from Eb and downwards came in bore sizes, which actually increased in increments of 0.5 mm:
MM Inches
17.0 0.669
17.5 0.689
18.0 0.709
18.5 0.728
19.0 0.748
19.5 0.768
20.0 0.787
20.5 0.807
21.0 0.827
21.5 0.846
22.0 0.866
The .689 bore was/is the standard for largish low Eb brasses (Besson compers, Conn 26K, 28K, and more) and for "consumer" BBb brasses (King tubas and sousas, the current Conn plastophone)
I have seen samples of the .709 bore, but cannot come up with names right now. The experts surely could do that.
The .728 bore is known from a number of for real BBb sousaphones from Conn (38K, 40K, 14K, 20K) and from the Besson BBb compers. The experts will be able to complete this list.
The .748 is known from one of my favourite BBb tubas, the German made York Master and from some of the Chicago York clones: Hirsburner and Nirschl.
You may find that the conversion table above here is a bit long, but I seem to remember, that the 5th valves of the York clones actually present such huge bores in their 5th valves.
Bore certainly is a factor in playability, feel, and sound. But truth should be honoured: My .728 BBb bass plays bigger than does my .748 BBb bass.
The reason may be, that the Conn 40K is quite short in sharp bends, even if it goes behind my back, while I am playing it. The .748 bore of the YM gives it great hall filling capabilities, an immensely easy legato, and great agility with much less edge, but also with a little less presence to the sound.
I have been political in this posting. I stand by that. What makes me cross is not, that I would like to deny the USians to elect their own presidents, if they would manage to count votes by general standards of arithmetic. But we have a clone as prime minister presently, and that surely is no fun.
I am all pro democracy, but I have to relay a true story from the first populist wave of ours some 3 decades ago:
A constituency in one of our outback provinces had elected a member of parliament with an IQ very close to his height as measured in inches. And he was no tall man.
A journalist approached the local chairman of the party in question and asked: How in H*** can you elect such an idiot?
The proud answer was: You surely are right, that he is an idiot. But we as his constituency feel, that he represents us very well!
The often referred to 1934 bass brochure can be downloaded in extenso from (if you sign up):
Conn bass instruments’ catalogue from December 1934. Thanks to the generosity of Rob Perelli-Minetti the YMPP project can present scans of a December 1934 Conn bass instruments brochure. 14 pages in B/W (1590K):
http://groups.yahoo.com/group/YorkMaste ... ochure.pdf
Klaus