2009 was a year of downsizing as the Ubangi-based horn system was disassembled and I started listening to ... headphones. This has been surprisingly satisfying, driven off either my 10Y-45 amp or the 01A-71A line driver (for 300 ohm sennheiser).
The headphone lineup has been expanded by a Lawton-modified Denon AH-D2000, similar to the LA-2000 but I did the Jena wire myself. This is pretty good, although rather zingy in the highs compared to the damped-sounding Sennheiser HD600. I'd look into the Lawtons if you are interested in headphones. However, in the end, the Sennheisers did better in comparison to the Lawtons than I expected. Different, of course, but not necessarily worse.
The electronics went through quite a bit of twiddling, after the 1970s-era Hewlett-Packard powersupply I was using as a battery charger went kerflooey, taking a set of batteries with it. Latest thinking on battery power supplies involves the use of screw-terminal sockets and in-line fuses on all batteries, and NO vintage powersupplies for chargers. Also, the battery grid-biasing on the tubes got upgraded to an adjustable potentiometer-based circuit, which allows exact individual biasing off a common -50V battery.
Despite knowing that I should just stick with the headphones, as they do sound just fine, I am still daydreaming about horns. Fortunately, I wasn't able to sell my 2x15" open baffle bass bin, which is now to be loaded with an Altec 416A and an Eclipse 15" sub each. I figure I can cross the 416 around 70hz on the low side, thus eliminating any need for baffle-related EQ. Below 70hz I can run the subs with about 1000 watts and eq like mad. Mids are to be some 400hz conicals for RCA MI-9584.
For now, running (24 ohm) headphones off the 8-ohm outputs of a 45 DHT amp is working fine. You need DC heating of course. Recommended ... but will expose flaws which can be incorrectly attributed to headphones.
Tripath 2020 and an old 1970s solid-state amp (SAE Mark IV DM) sounded like dog doodoo on headphones.
