Listening #110 Page 2
The first Haut-Brions (footnote 2) used two output pentodes and two 6AW8A triode/pentodes per side, with negative feedback applied only within the input section. After one or two production runs, Ken Shindo introduced some unheralded changes: Two of the four 6AW8A triode/pentode tubes were replaced with 6EJ7 pentodes, andmore radicallya small amount of global feedback was introduced, from the output-transformer secondaries back to the pentode halves of the 6AW8As. The latter change in particular was credited for making that version of the Haut-Brion more loudspeaker-friendly than its immediate predecessor. No specs are available for the Shindo-designed Lundahl output transformers, but while measuring that version of the amp I noted significantly more output power driving a 16-ohm load than an 8-ohm load.
That version of the Haut-Brion sold out last summer, prompting Ken Shindo to take yet another fresh look at the most expensive stereo amp in his product line. The new Haut-Brion, which became available in late September, has a number of things in common with its immediate predecessorand 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 Y denotes 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 signalunlike Shindo's similarly powerful Corton-Charlemagne, the Haut-Brion is not an Ultralinear designand 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 predecessorand other Shindo modelsthe 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.
Speaking of gain, it's worth mentioning that all contemporary Shindo amplifiers are three-stage (as opposed to two-stage) designs, and they all tend to have significantly higher gain than most other commercial amps. For that reason, Ken Shindo's amps are equipped with left- and right-channel gain controls, so the user can adjust gain and channel balance in accordance with his or her system and room. That brings to mind another change in the new Haut-Brion: Every other Shindo amp I've tried has sounded its best with its level control(s) turned all the way up, and with only the preamp control used to adjust volume. But in the new Haut-Brion Ken Shindo has exchanged his usual Cosmos potentiometers for a pair of Alps 250k ohm potsand I found that I could adjust the new amp's level controls with absolutely no diminution of clarity and presence. Among other things, that allowed me to raise my preamp level to a range where channel-to-channel tracking is much better. (I admit: I'm a balance freak.)
Every Shindo amp I've experienced has also had a characteristic sound, and the Haut-Brion is no exception. Each Haut I've heard, regardless of version, has sounded bignot in the somewhat puffy manner of other amplifiers, but solidly soas well as timbrally rich, and slightly darker than average. Notwithstanding that last quality, they've all been well detailed, without blurring or smoothing over textures, although other Shindo amplifiers can sound stringier or reedier when need be.
That handful of Hauts equipped with global feedback deserve special mention: They don't sound quite as big as the ones without, and they sound considerably tighter and faster. The first such Haut-Brion I had in my system was, quite simply, the rockingest Shindo amplifier I've heard, yet it still delivered the abundant tone and touch for which the brand is known.
The new Haut-Brion lacked that tightness, and the low-frequency tones of some instruments had very generous decay times. But it generated the most enormous soundfield I've ever heard in my homefar bigger than even my own Shindo Corton-Charlemagnes. Even more noticeableand more impressivewas the manner in which the latest Haut-Brion communicated the idea of force. The amp was, among other things, the pizzicato king: When a string instrument was plucked through the Haut-Brion, it stayed plucked. I heard a fine example of this while listening to the Scherzo of Britten's Serenade for Tenor, Horn, and Strings, Op.31, with Robert Tear, Alan Civil, Sir Neville Marriner, and the Northern Sinfonia (LP, Angel S-36788). Nuances of touch on virtually every instrument, from fingers on a nylon-string guitar to wooden sticks on a drum kit, were laid bare as never before. It struck me that the switch to the Haut-Brion was not unlike swapping my two-way, dynamic Audio Note AN-E loudspeakers for a pair of horn-loaded compression drivers. And that thought led me to wonder if the combination of a Shindo Haut-Brion and a good pair of horns might result in some sort of impact overdosethe prospect of which, I admit, has tremendous appeal.
Finally, there's the matter of styling. The original Haut-Brion appealed to me from the first, partly for looking like no other power amplifier I've seen, partly for the cleanness and simplicity of its design: What appeared, from the outside, to be a single, seamless box was actually a six-room housethree up, three downwith all the signal tubes arranged neatly behind a central Plexiglas window. The new Haut also works as architecture, although this house is more in the Federal style (save for a slight departure from symmetry). Here the box has been replaced with a somewhat more traditional low-slung chassis, also divided into three downstairs rooms, the left and right sides of which are topped with removable transformer covers of mildly unequal size: mains transformer and power-supply choke on the left, output transformer and reservoir caps on the right. Ten tubes live in the breezeway between those structures, the whole topped with Ken Shindo's most fanciful tube cage yet: a domed affair, the untethered front of which suggests the visor of a green medieval helmet. Way cool.
Footnote 2: The Haut-Brion's early history is hazy, but there are rumors of an even earlier version than this, possibly designed around a different power tube.