Shindo Laboratory Haut Brion
The new Haut-Brion, which became available in late September, has a number of things in common with its immediate predecessor—and just as many differences.
First, the similarities: As with every other Haut I’ve seen, the new one uses as its output tube the comparatively rare 6L6GAY. (The GA indicates the envelope’s size and Coke-bottle shape; the Ydenotes a tube base made to military specs from Micanol, a reddish-tan, high-temperature phenolic that is no longer produced, and whose name has since been appropriated by the makers of an anti-itch cream.) The output section is a fixed-bias design, with a regulated bias supply and individual adjustment pots for each of the four tubes; hefty 1-ohm cathode resistors on all four output tubes simplify the taking of bias-current measurements without lifting those cathodes appreciably above ground. There’s regulated DC (about 260V) on the screen grids of the output tubes, but no signal—unlike Shindo’s similarly powerful Corton-Charlemagne, the Haut-Brion is not an Ultralinear design—and those screen grids are all tied together.
The new Haut-Brion also uses the same output transformer as its predecessor: a C-core Lundahl model made exclusively for Ken Shindo, to his specifications. Each transformer has only a single secondary coil, which I would assume is optimized for high-impedance loudspeaker loads such as Shindo’s own. The Haut-Brion’s exceptionally large Denki mains transformer also appears unchanged from the previous version, as does its large power-supply choke. The new Haut-Brion also shares with its predecessor—and other Shindo models—the use of an internal EY88 diode tube, tied to a center tap from one of the mains secondaries, to gradually ramp up the rail voltage in an effort to prolong tube life. All power-supply rectification is accomplished with silicon devices.
Now for the differences. First and perhaps most important, the new Haut-Brion does not use global feedback, making it less suitable than its predecessor for very demanding loudspeaker loads (but see below). Second, Ken Shindo has abandoned the 6EJ7 for this design and reverted to 6AW8A triode/pentode tubes, this time three per channel. As with other of Shindo’s driver circuits, I was unable to fathom the intricacies of this one, apart from noting that there does indeed seem to be some local feedback. Surprisingly, given that there are fully three triode/pentode tubes per channel, this iteration of the Haut-Brion didn’t appear to have any more gain than its immediate predecessor.
6L6G push pull stereo amplifier utilizing RCA output valves for 25 watts per channel. Full, rich and incisive with excellent flow and natural detail. .