In sci.electronics.design Tim Wescott wrote:
Are there, by any chance, kits out there?

Google says there is a "headphone preamp" kit for $60 to $70 that uses
2x 6N3 for stereo. (Google "Sainsmart 6N3" or "Riorand 6N3"). I can't
find an output power spec, though. There is also an "Indeed/Bravo"
stereo headphone amp talked about on forums, which apparently has 12AU7
and 6922 versions. Not sure on the output power or where to buy. After
that, prices seem to start at $150 for one channel and head skyward
from there.

Suggestions welcome.

Use toobs that need 5 V, 500 mA or less at the filaments and you can
power each filament off of a USB port! Or, ask Antec if they have a
PC power supply with DC outputs at +200, +12, +5, +3.3, -5, and -12 V,
and an AC output of 6.3 or 12.6 V - Chinese engineers need to laugh too!

Buy a couple of old toob radios at the thrift store and use the best
power transformer (get ones that have one), both output toobs, and the
chassis to roll your own? Schematics for old radios are pretty easy to
find on the interweb.

Matt Roberds