Whole hog (included DAC, tube totally invisible):
RWA Isabellina HPA or Audeze Edition: (Chassis is open to view internals, its just a nondescript black box normally)
Without a DAC:
Completely hidden:
Cary HH-1:
Ear HP4:
Audio Note's new HE-6 amp:
Windows:
Including DAC:
Peachtree products (there's a few, lots of versions, here's the idecco, DAC/headphone amp/speaker amp)
Windows no DAC:
There's the LF:
The Vincent KHV-1 (actually fits well for compact width as its set up
vertically)
Cayin HA-1a (similarly vertically arranged, two levels if you look at the internals
Novel take on windows, with DAC:
Woo WA7: (tubes encased in plastic, small holes on top for ventilation/rolling)
Then there's amps with just the tops of the tubes visible, for those who think that 'just the tip' doesn't count:
ECP L-2:
Lyr/Valhalla:
There are also cheaper options in the same spirit of the ECP in most builds of the SOHA, CTH.
Grates:
Luxman SQ-N10
(Has a removable grate that effectively hides the tubes. Has ipod dock as well as phono stage, optional DAC)
ALO also showed off a new amp with a grate option recently, it may have been an early version of the Studio Six amp.
This bellari amp wears a hat to disguise it's tubinity. All it needs is a fake mustache and it will be unrecognizable as a tube amp:
Another option is a portable hybrids, such as Jaben's portatube, millet's portable hybrid tube amp, or ALO's portable tube amp (Continental I think its called)
Oh, and the category I almost forgot:
Pyramid shaped amps that light up like they belong on the strip in Vegas:
Music Hi Fi Orpheus:
I'm sure I'm missing some but these are all off the top of my head. Three more things to note: 1) most of these are hybrids, so they do "have tubes" but maybe not the qualities you are looking for, and 2) These were not mentioned in any kind of order of preference sonically. Just a list of amps that may fit your terms. 3) Some well regarded "real" (non hybrid) tube amps may have options for covers/grates if you contact the manufacturer.
A word of advice:
Many who are in an office environment are reticent to have a tube amp on their desk for fear of looking weird in the eyes of co-workers or due to office restrictions and regulations. I have found a very simple workaround for this: managing expectations and priorities. There are many ways to accomplish this, but personally I always keep a severed head on my desk to distract from my tube amps. As a result, I have managed to get away with this at work with no reprisals:
Its a bit of a pain to keep bailing myself out of prison on suspicion of murder, but the last thing my co-workers notice are my atma-sphere ma-3 monoblocks.
