For those of you who believe that adding a fifth valve makes a tuba stuffy...

[bloke]

... this one has to be super unstuffy:

https://www.ebay.com/itm/304773772407

[Casca Grossa]

Who needs four valves...or five for that matter?

[UncleBeer]

Heck: Don Butterfield had the 4th valve taken off of one his horns; claimed it was superfluous.

[bort2.0]

German kids' tuba.

[bloke]

.5mm thick sheet metal tubas with 3 rotors are easier to march with.

Bugle corps instruments only had 1 valve at first.
Bugles had no valves at first - so why are they stuffy?

[jtm]

.5mm thick sheet metal tubas with 3 rotors are easier to march with.

Bugle corps instruments only had 1 valve at first.
Bugles had no valves at first - so why are they stuffy?

They're stuffy because they're pitched three half-steps lower than they should be.

[bloke]

yep...and B-flat-and-shorter-trumpets (or other shorter-than-pitches-in-G brass) aren't NOT stuffy (double negative) due to any "valves" issues.

Conn (King) 5XJ tubas:

People claimed that their 5th valves made them "stuffy", and taking them off solved that.

I suspect that - mostly - that was tactile, as the 5th LEVER system on those was designed so poorly (probably causing many players to tense up when playing pitches which involved the 5th valve).

Another factor could well have been dealing with an 11/16" bore - after being accustomed to one or more tubas with 3/4" or larger bore sizes.

The 5th valve on this tuba (a bit smaller than a 5XJ, yet longer) is FINE...and/but I'm not trying to blow the crap out of this thing (as if it was my Miraphone model 98).