Sorry that you had problems, but I know it is not the fault of the design as we can drive any amplifer that we have tried with excellent results and all of their units get consistently outstanding reviews from everyone (aside from you of course). They do have headphone outputs and it is included in the spec sheet. They can also produce up to 30v of output and are only 100 ohms at 1.5v. Your measurements are either totally inaccurate or you had a problem with the unit. It's only real flaw in my view, is the choice of the 6SN7 tube for the linestage, which are easily damaged and can be difficult to find good examples of. They were chosen for their sonics, not their popularity. The amplifier itself is exceptionally well built and will wear very well. If anyone has any doubts as to the true specifications or capabilities, the electrical engineer Mark O'Brien, is very easy to talk with and can provide many references of satisfied users and of real world performance results.
-Bill
it certainly is possible that i had a bum unit, but i wonder, since i had it shipped to mark o'brien before i took delivery, cuz i wanted a second set of outputs installed. (which could add further to the impedence issue, as this effectively doubles the pre's output impedence, when in use. even mark suggested i disconnect the second out, to see if things would improve.)
re: my "measurements", i do not recall the walue of resistors i used, but i used them to cross the outputs, to see if i could hear an audible spl drop. dennis had of cary walked me thru the procedure, to help me determine what walues to use, & what it meant when i heard a drop in sound level. it was a few years ago, & to be honest, i do not remember. all i remember is the easily audible drop in spl, w/the resistor walue i used, indicated an actual output impedence of ~2.5kohms.
re: the 6sn7 tubes, i purchased some spendy ge nos tubes to try w/the unit prior to selling it - i really *did* wanna give this unit a fair shake. they were certainly a bit better than the stock tubes, but not enuff to make me wanna keep the pre. and, the pre is still microphonic as all get-out. yust the slightest touching of the pre could be heard thru the speakers. and, any reostat-controlled lighting in the house had to be either turned off or all the way on, as these could also be heard thru the speakers, even tho i was using power conditioning.
in all fairness, i know a lot of folk like this pre, so i think synergy is at play here - as is the case w/much of audio. but, i really think this pre will have a hard time w/long ic's to an amp, especially w/amps that have input impedence <25kohms. and, i have received a number of private emails regarding my comments from rogue owners that sold their pre's cuz of experiences not all that different from mine - especially the microphonics issue.
regards,
doug s.
