The Linear Tube Audio preamp use the 6 sn7 tube,as well as a second set of tubes I think like 12at7 and get T with the Lundahl transformer ,it has 3 position switch inside for gain inside to work well with tube or SS amps in the future most Donot.
it uses premium parts throughout and U.K -Top Clarity CMR output capacitors
a excellent Resistor ladder volume control , not a cheap Alps volume pot like many
several stages of regulation ,and Originally designed by David Berning,then upgraded still for under $6k a exceptionally well built preamp !!