Listening #26

It's a strange sort of progress: As culture and commerce evolve, most people look for simple, easy solutions to their needs. Enthusiasts, however, go out of their way to complicate matters, often choosing products that are expensive and difficult to use. Nowhere is this more obvious than in the world of home audio, where typical consumers have embraced the notion of smallish, self-contained music systems—yet audiophiles, who are surely as crazy as bedbugs, seem bent on parsing an ever-increasing number of individually distinct products from the basic concept of a music system.

Remember one-box CD players? They're hard to find at some price points these days, partly because most households already have at least one CD player as an integral part of some other appliance—computer, clock radio, boombox, DVD player, whatever—and partly because audio enthusiasts at the other end of the spectrum are increasingly interested in multibox digital front-ends, with separate transports, converters, upsamplers, and clocks.

I'm not letting vinylphiles off the hook by any means. I began my adolescence with a nice, neat record player that had a built-in tonearm with a built-in ceramic cartridge. Then I bought a Dual changer and a separate Audio-Technica cartridge, which I remember liking. Years after that, I had an early Rega Planar 3, which I "upgraded" with a separate Grace tonearm and a series of different cartridges. Now I own a Linn Sondek LP12, on which platform I've had, at one time or another, five different tonearms, dozens of different cartridges, four different mats, two different sets of feet, two different top plates, four different motors, three different tonearm cables, one onboard phono preamp, and six different power supplies. (I admit to being one of those analog enthusiasts who actually took it as a compliment when Herbert von Karajan said of the first CD players, "All else is gaslight." What's wrong with gaslight?)

Lately, it's the power supplies I find most interesting: They will surely be the next analog products to earn a category of their own, beyond the accepted divisions between turntable, tonearm, and cartridge. And I wouldn't be surprised to see the 2006 Stereophile Buyer's Guide rearranged to accommodate them.

Turntable power supplies also fascinate me for their influence on music reproduction, both in theory and in practice. As for theory, think back to the Tiefenbrunian notion of phonographic hierarchy, whereby the machine that drives the record is of greatest importance, the thing that holds the transducer comes after that, and the transducer itself comes last. Surely the thing that drives the thing that drives the record belongs at the top of the pecking order.

And as for practice . . .
Of the six different LP12 power supplies I've used, two stand out in a commercial sense: Linn's own Lingo ($1600) and the Naim Audio Armageddon ($1550). One is a very sophisticated product; the other is a simple product of sophisticated thinking.

Let's start with the one that's named for the end. In the late 1980s, Naim Audio developed a pair of modifications for the Linn LP12: an onboard moving-coil phono preamplifier and an outboard turntable power supply, the latter intended to replace the LP12's then-current Valhalla motor-drive circuitry. Naim apparently didn't intend them as commercial products, but dealers and reviewers who heard the mods were so impressed that they convinced the company to offer them for sale, which Naim eventually did: In 1995 the onboard preamp was introduced as the Naim Prefix, and the outboard motor supply got to keep the name that had originally been applied, if half-jokingly, to the combination as a whole: Armageddon (footnote 1)—as in, the last turntable mods that you or anyone else will ever need.

The Armageddon is about as simple as they come. Apart from various fasteners and connectors, the chassis contains one resistor, two capacitors, and one transformer. (That's four parts total, in case you weren't counting along.) The resistor and capacitors comprise a simple, passive phase-shift network, in-line with one of the motor's two phases: It tells the motor which way to turn. The real star is the trannie, a 500VA toroidal monster that accounts for most of the Armageddon's weight. Its job is that of an isolation transformer: Household AC travels through the primary coil, doubtlessly overlaid with noise products of the usual sort, and that current creates an electromagnetic field; the field cuts through the secondary coil and induces an identical current there—minus, it is hoped, the noise.

The new current isn't precisely the same as the old one. Because no product of human industry is perfectly efficient, not even transformers, one can expect to lose some voltage in the form of vibrational energy and heat. My measurements of the Armageddon, such as they were, bore that out: When I put in 123V AC, I got back a little more than 112V. Still not a bad rate of exchange—and evidence enough that Naim's trannie is configured as a unity device, at least in the US. (In the UK, with its 240V AC supply, it acts as a step-down transformer.)

The Naim Armageddon package also includes a small circuit board, designed to snap on to the fasteners that would otherwise affix a Linn Valhalla or similar board to the LP12's main support beam. This new board has solderless connectors for the four motor leads, and acts as the terminus for a hefty umbilical containing four separate conductors: two AC hot leads (one of which is phase-shifted), one AC neutral lead, and one electrical ground. In a typical setup, one would connect the electrical ground to the LP12's front-most support bolt, along with the tonearm and subchassis ground leads. (Keep in mind Naim's enthusiasm for star-ground schemes—in which sense that front bolt becomes the single, central grounding point for an Armageddon'd LP12.)

So much for a typical setup: In an American setup, the user must also acquire a 60Hz version of the LP12 motor, which you can buy from Linn. (The "60Hz" is a misnomer, of course: All LP12 motors are designed to work on 50Hz AC, but if you want to drive an LP12 direct from 60Hz household current and still run at more or less the right speed, you need to compensate by topping the now too-fast motor with a smaller-than-normal pulley.) Most LP12s come with a 50Hz motor as standard, because their power supplies create their own 50Hz reference—but an Armageddon power supply does not. Store all that away for later.

One other thing deserves mention: In addition to filtering out noise in a manner that neither impedes current nor adds any apparent new noise of its own, an isolation transformer like the one in the Armageddon has a unique advantage: the ability to drive an AC motor more efficiently, by being a better impedance match with the coils of the motor, much as a single-ended-triode enthusiast might try to match the voice-coil of a loudspeaker with just the right output transformer.

The technology behind the Linn Lingo is a great deal less obvious. As with its predecessor, the above-mentioned Linn Valhalla power supply, the Lingo is a motor-drive unit that synthesizes its own 50Hz reference signal, regardless of the country in which it's used. But removing that circuitry from the turntable proper and putting it in a separate box gave Linn's engineers an opportunity to do a bit more than just that—and they took full advantage of it.

Like the Valhalla, the Linn Lingo uses a crystal oscillator to generate its reference signal, but the active filtering used to strip the resulting squarewave of all its harmonics is much more sophisticated in the Lingo. The Lingo also feeds that signal to two separate class-A amplifier circuits, one for each of the motor's two phases. Doing it that way allows the Lingo to maintain a very precise 90º between the two signal phases, which goes a long way toward eliminating motor vibration—much more, Linn says, than a comparatively imprecise passive phase-shift network.

The Lingo has other tricks up its extruded sleeve. While designed to maintain a rock-steady output frequency, the Lingo actually varies its output voltage—and thus motor torque—in response to need. On startup, the Lingo's voltage is set for maximum, but once the platter gets to 33.3rpm, the voltage is reduced to produce only the amount of torque needed to maintain a steady speed. Also, pushing a single button can tease a 67.5Hz sinewave out of the Lingo—which is precisely what that 50Hz motor requires to spin the platter at 45rpm. Take that horrid old 45rpm pulley adapter and toss it in the dumpster.

If you buy a Linn LP12 with a Lingo supply as standard . . . well, there you go. But if you buy a Lingo upgrade for an LP12 that's already in service, then you'll get more than just the outboard box itself: You'll get a new on/off switch, a new power-supply umbilical cord, and a new turntable circuit board, too. The latter is similar to the one that comes with the Naim Armageddon, in that it serves only as a junction for connecting the motor, switch, and power supply together.

The things I listened to
A comparison of the Lingo and the Armageddon is something I've been working on in the background for about two years, during which time I've made dozens of pages of listening notes. And in the past month alone, I've done four full setups on my LP12, trying and comparing all the possible combinations that might affect my conclusions, the constants being the Linn Akiva cartridge and the LP12 itself. Good thing I bought that Linn setup jig back when they were cheap.



Footnote 1: But, as with the Naim Audio Tonearm, it was a long time before Naim officially gave the Armageddon a name: For years, it was simply called the NAPSA, for Naim Audio Power Supply, Analog.
ARTICLE CONTENTS
Share | |

X
Enter your Stereophile.com username.
Enter the password that accompanies your username.
Loading