I have spent more than a thousand hours with the same pair of Soviet 6BE6 tubes in my LDIII, , fed by a Turtle Beach DSS2, a Carver TX11a tuner or an IAudio 10. Headphones are my Martin Cocobolo shell Turbulent X cans. The electricity is via a dedicated 15 amp circuit with a Tripplite hospital line conditioner.
Power tubes are Soviet 6N6P mil-spec matched set from the 1970's. These have been in this amp for the past two years.
For Big Band, Swing, Folk, Spoken Word, World Music (Niyaz, Deva Premal, Dead Can Dance) and ethnic music of various sorts, this combination is sweet, accurate, non-fatiguingly crisp with good separation. The limiting factor so far as I can determine lies entirely in the source material. I put a signal generator on the input and stepped the amp through it paces with sine sweeps, square waves, etc. and could find no flaws or distortion from 38 Hz to 22 Khz.
Much of the existing Old Time Radio source material around has unfortunately been compressed multiple times with MP3 encoders, resulting in a "breathy and clicking" quality that is annoying. The only commercial recordings that approach this are those from Chrysalis. The downloadable Steeleye Span albums in mp3 format butcher Maddy Pryor's voice by introducing distortion that makes her superb voice seem to chatter or miss parts of a note. These flaws are not present in the cassette, LP or CD versions of the same recording.
My amp is coming up on its fifth birthday, and aside from adding tick marks on the volume control with a Sharpie, it is unaltered from the day I un-boxed it. The volume control is starting to make a bit of noise from time to time, so it probably will get a shop visit later this year.
While better audio gear probably exists out there somewhere, I'm not sure I could get more value for my dollar than I have with my current setup nor am I certain I could hear the difference. I've got replacement tubes packed in cotton and cardboard for that day when the current sets expire.
Anyways, that's my extended listening session report.