there are more tube headphone amps and solid state headphones amps out there than you can shake a proverbial stick at.
making an assertion either way - that tubes sound better or that SS sounds better - is foolish.
the sound of any amplifier will be the result of its circuit design, signal path, the quality of the components, etc.
why do amps sound different? signal loss is the number one reason.
you see, not every amp is able to "carry the bag of sand" (the full signal) all the way to the finish line without losing some sand.
now, about tube rolling.
the tube used in the amplifier is a critical part of this job of amplifying the signal without loss. or without introducing negatives, for that matter.
input tubes, output tubes, power tubes, driver tubes. whatever you want to call them.
it is beyond argument that some tubes are better made than others, and these tubes better fulfill the duty of amplifying the signal while retaining the most information.
some years ago, tubes were made more carefully. air was depleted fully from the glass enclosure. pieces were more carefully chosen and crafted.
so, the tube will SOUND better than a modern Russian or Chinese equivalent design.
now, is it practical to buy a cheap headphone amp, and spend more on tubes than the amp? No.
will the amp sound better? likely yes. but impossible to say.
will the amp with its "rolled" tubes sound better than a SS amp of similar $? once again, impossible to say.
Edited by TheWuss - 2/7/13 at 9:40am