August 2003

Linn Klimax Twin Stereo Amplifier

by John Leosco

Review Summary Sound "Comes as close or closer than anything else I’ve heard to the ultimate goal of no intrinsic sound"; "starts with a background of nothingness, a void. Any sound set in opposition to the stark background stands out in vivid contrast, and the amp's quick response only acts to intensify the effect." "If the Klimax Twin lacks anything at all, it’s the last degree of palpability or body in the midrange." Features Class-AB MOSFET switch-mode power amp that delivers 100Wpc at 8 ohms, 230Wpc at 4; cooling is handled by " a flue of sorts right down the center of its elaborate casework" and an internal fan; "like a Fabregé egg, [the Klimax Twin's] gorgeous compact metallic shell radiates a jeweler’s artisanship." Use Not much rear-panel space -- "let’s not even discuss biwiring." "Especially when the amp is playing full-range or bass-heavy music at realistic levels, the fan in the Klimax Twin would start whirring away about half of the time. Inaudible during all but the softest passages, the cooling fan could be clearly heard between songs." Value "What the Linn Klimax Twin does offer is superb definition, a lack of obvious character, and overall balance -- in spades. Those sonic characteristics not only separate the Linn amp from much of the field, but also place it among audio’s elite."

Quick! If I say "high-end solid-state amplifier," what shape springs to mind? Probably a megalithic block fronted by a stout faceplate and flanked by countless rows of heat-sink fins. Or possibly, if you’re a modern sort, a towering vertical case closely resembling the business end of your PC. The Linn Klimax Twin takes neither of these forms, but make no mistake -- it is high end through and through.

Form follows function

At $8995 USD, Linn’s Twin certainly costs high-end dollars and looks the part, too. Like a Fabregé egg, its gorgeous compact metallic shell radiates a jeweler’s artisanship. Casual glances reveal no seams. Only a single blue stylus-shaped LED graces its face. Rounded edges everywhere and a silky feel make the 20-pound stereo amp a tactile delight.

The 13 3/4"W x 14"D x 2 3/8"H squarish enclosure is no eggshell, however, as a firm rap finds the two-piece chassis inert. Each half is precision-machined from solid aluminum alloy and then hard-anodized. Integrated, the dense shell obviously protects the internal circuits, but it also enhances performance by resisting vibration and shielding electrical interference.

Powerful amplifiers must dissipate heat. The Klimax Twin has a flue of sorts right down the center of its elaborate casework (Linn calls it a heat exchanger). Precisely bored into the top are 14 slits for ventilation, and underneath an array of slots and contours direct airflow. Under normal conditions, the high thermal mass of the case absorbs heat from the close-coupled circuitry. Heated air rises from natural convection drawing external air up and through the middle of the amplifier; thus, to cool properly, an ample supply of fresh air is required. Stacking the amplifiers, placing them in an enclosure that restricts ventilation, or enthusiastic play may increase internal temperature until an interior fan spins up to supplement airflow. Under extreme conditions, the amplifier is thermally protected and will shut down until its touchable surfaces reach a safe enough value to meet international safety regulations.

Bisected by the fancy flue are two pint-sized tightly packed circuit boards. One board supports the power supply, while the other holds the audio circuitry. According to Linn, keeping the signal path as short and simple as possible ensures that the amp generates and receives the absolute minimum level of electrical noise.

Switch-mode power supplies aren’t new and have been used in computers since the 1960s, but high-power applications, especially in audio, have always been limited. The potential disadvantages of high-frequency noise, complexity, and unacceptable engineering costs have far outweighed the advantages of high efficiency, fast response, and load tolerance. But Linn felt the benefits were well worth the effort.

In the Klimax Twin, an automatic internal mains-voltage switch allows operation with a mains supply ranging from 90VAC to 260VAC. The switch-mode power supply first filters then rectifies the incoming AC, converting it to a lethal-if-touched 300-350V of DC, connected directly to the incoming mains. This high voltage is cropped by blindingly fast 20nS semiconductor switches and applied to a tiny (1 1/2") transformer. At 50 or 60Hz, the mini transformer could only deliver about 5 watts of power, but due to the rapid switching in the Klimax Twin, it can deliver 1000 watts. The transformer changes the voltage to a level the audio circuitry can use and isolates everything downstream from the mains supply. On the output of the transformer, very fast rectifiers convert the high-frequency waveform back to DC, and a small coil and thimble-sized caps filter the power for the audio circuitry to draw from. Linn says, "By controlling the timing of the switches, the output voltage can be held constant or varied, as required, without the need for further inefficient voltage regulators. This processing all happens well above the range of human hearing."

The audio circuits utilize three monolithic (single-chip) power devices per channel that, according to the company, "contain all of the audio circuitry of a power amplifier in a few square millimeters of silicon." The power-output stage of the chip is a MOSFET-based design biased in class AB. In addition, the Klimax Twin is direct coupled with no capacitors in the signal path. Specified to deliver 100Wpc into 8 ohms and 230Wpc into 4 ohms, the amplifier is not current limited. A protection circuit monitors the output current to determine if it’s safe or not. Either all the current requested by the load is delivered, or the amplifier stops amplifying.

Form inhibits function?

Around back, the cooling-fan inlet divides the rear panel into two scant 5" x 2" sections. What’s more, the top overhangs the back by about 2 1/2", creating two caves within which connections must be made. One recess surrounds the single-ended RCA and balanced XLR inputs, both with a specified input impedance of 7.8k ohms, and an itsy-bitsy pushbutton for input selection. Gain is specified as 28.6dB single-ended and 22.6dB balanced. Squeezing my finger between the cover and the jack to release a balanced interconnect was not easy.

The other pigeonhole holds two pairs of binding posts, an IEC mains socket, and a power switch. JPS Labs Superconductor+ Petite speaker cables are just that -- petite with limber ends, not to mention that they sound good. The JPS Labs cables worked fine, but even then, wedging my pinkie past to touch the power switch was a struggle. Yes, my fat and stiff Synergistic Research Designer’s Reference speaker cables would barely connect, but they weigh about as much as the Klimax Twin. I uttered enough four-letter words during the hookup phase to make a longshoreman blush. Let’s not even discuss biwiring. I always thought modular components were about flexibility and breaking down barriers, not erecting them. Even beauty has its price.

A sensing circuit automatically flips the Klimax Twin into standby mode if no signal is present at the inputs for ten minutes, drawing only 18W of power and dimming the pretty blue LED. A signal or noise greater than 150uV turns the amplifier on after about a one-second delay. The first CD of the day means either missing the initial burst of music or starting over.

While driving my B&W Nautilus 801 loudspeakers or the recently reviewed Ascendo System M, the Linn amp was normally warm but never hot to the touch. The amp was placed out into the room with unobstructed airflow. The lower air density at 6000 feet of elevation where I live may decrease the Klimax Twin’s ability to cool itself. Especially when the amp is playing full-range or bass-heavy music at realistic levels, the fan in the Klimax Twin would start whirring away about half of the time. Inaudible during all but the softest passages, the cooling fan could be clearly heard between songs. Of course, natural convection was silent with background-music levels. At no time did the amplifier shut down, either from thermal or over-current protection.

The rest of my review system consisted of a PS Audio Lambda CD transport feeding bits through an Illuminations D-60 coaxial digital cable to a Dodson Audio DA-217 Mk II D digital processor. An Ayre K-1x preamplifier routed analog signals through single-ended and balanced AudioQuest Diamond interconnects. An API Power Wedge 116 conditioned AC power to the front-end components. Comparison amps were an Ayre V-1x and a Krell KSA-150.

Linning

I had to spent a bit of time listening to figure out how the Linn amp does what it does. It appears that the Klimax Twin starts with a background of nothingness, a void. Any sound set in opposition to the stark background stands out in vivid contrast, and the amp's quick response only acts to intensify the effect. Needless to say, the Klimax Twin is a revealing amp, but fortunately it’s not a merciless one. Highs are extended and expansive, yet pleasing to the senses. Its frequency response sounds balanced without any single bands taking precedence over any other.

Direct from Europe, Shania Twain came knocking with her popular fusion of country and rock. From Up! [Mercury 088 170 314-2], the punchy, throbbing bass lines immediately got my foot a-tappin'. Twain’s exciting vocal, pinpoint placed, amidst a highly distinct supporting cast was an exhilarating, dynamic mix through the Linn amp. Her catchy tunes electrify like the high-voltage outfits she wears. Yow!

One example of an excellent acoustic recording is Marian McPartland’s Hickory House Trio - Reprise [Concord Jazz CCD-4853-2], and the Klimax Twin does it proud. From speaker to speaker, a wide, deep space is re-created containing a crowded room with well-defined boundaries. McPartland’s piano sounds nearly real within that room since the semi-focused fundamental tones and harmonics develop just right, the notes cascading midway across the stage. Joe Morello’s sticks smacking the drum skins can be startling in their immediacy and are precisely located. Cymbals ring true with sparkle as they traverse the soundfield. Applause at song’s end is spookily genuine. As cocktail glasses clink in the background, I can close my eyes and imagine myself seated at a small table in Birdland, New York City. I was applauding, too.

Bill Crow’s vibrant bass claims the middle with control, robust form, and a realistic feel. By comparison, the worthy Klimax Twin also finds itself in the middle since it does not possess proverbial Krell-like bass, which is even tighter and has greater impact, nor does it have all the reverberant glow of the Ayre V-1x. Nevertheless, the Linn’s lows are solid and striking by any measure.

Back to Twain and McPartland -- music from two very different artists and two totally independent outcomes from the Linn. Some amplifiers display a signature, a consistent character from disc-to-disc. Ideally, I suppose, the response should solely depend on the source material. The Klimax Twin comes as close or closer than anything else I’ve heard to the ultimate goal of no intrinsic sound. I hesitate to call it transparency because I don’t want to imply any negative connotations surrounding that word, like glassy, thin, or insubstantial. The Klimax Twin is none of those. It simply allows the music to pass through -- albeit with amplification of the signal along the way.

From October Road [Columbia CK 63584], James Taylor relaxes at center stage. Well into his 50s, the intoxicating tenor sounds pure and articulate, and hasn’t lost a step in over 30 years. Taylor’s vocals engage by dint of a suave, natural aura. Guitar strums throughout are well defined and harmonically dense, the tones fraught with color -- color without colorations, that is. On "Belfast to Boston," an airy and open soundstage spreads nearly wall to wall with the chorus dispersed across it. Crisp military-style snare drums rat-a-tat, but their rolls are smooth.

If the Klimax Twin lacks anything at all, it’s the last degree of palpability or body in the midrange -- one subtle distinction between outstanding hi-fi and real life. But take note -- I’m comparing the Linn amp, within my system, to live music and not to any other audio gear. It is possible the amplifier is transmitting exactly what it receives, and anything else is distortion. I normally wouldn’t say that, but the Linn Klimax Twin twisted my arm. It’s that good.

Twins

While comparing the Linn Klimax Twin to my equally priced reference amplifier, the Ayre V-1x, I couldn’t help but think that some skeptics would have a field day with this pair. Although entirely different on the outside and of disparate genetic code within, if you listen, the two amps are virtual sonic twins. I can hear the scoffers now: "Jeez, the Ayre uses a huge transformer and a slew of reservoir capacitors. The V-1x dwarfs the Linn. How, pray tell, can they be so audibly similar?" Or, worse yet, "Any competently-designed amp will sound the same." Heaven forbid -- might the second heathen be right?

The Klimax Twin and the V-1x aren’t identical twins, however. Run single-ended, the Linn is a touch quicker and cleaner and with greater contrast between its plausible images and silent background. The V-1x is richer and fuller with a bit more resonance. The Klimax Twin sounds precise, and the Linn’s performance doesn’t change one iota from single-ended to balanced operation.

Fully balanced, the Ayre edges even closer to the sound of the Linn. The slight margin evaporates, and the two amplifiers sound almost indistinguishable. At the end of the day, I’d say the Klimax Twin is just an eyelash more succinct. Honestly, I had to swap back and forth dozens of times to confirm these variances. Flip a quarter -- it’s a whole lot easier.

Where the two amplifiers truly differ is in form and functionality. Because of its fly weight and trim size, the Linn allows for placement in a variety of settings you’d never even consider for the massive Ayre -- as long as ventilation is adequate. The class-A-biased V-1x could double as a space heater, while the more efficient Klimax Twin sheds considerably less heat, but isn’t always quiet about it. The Linn turns itself on after a second or so of music. The Ayre must be activated manually, either by remote control or the flick of a switch.

The vast expanse available on the back of the Ayre V-1x coupled with the nifty Cardas-sourced binding posts make cable swaps and biwiring a snap. For an equipment reporter, this is a must-have feature. Earlier, maybe I was too hard on the Klimax Twin. An average consumer will likely hook up cables once or twice and then simply revel in the profile of Linn’s sleek visual lines.

High-end

What’s the job of a high-end amplifier? Although the answer seems obvious, I’ll state the obvious and say an amplifier is a device that can effectively drive the loudspeakers the owner loves to hear. To be effective, first and foremost, the amp must do no harm; it must let the music come through unscathed. If that isn’t enough, I’ll also add that to be considered high end, the component needs to do something sonically to distance itself from the pack. The Linn Klimax Twin meets these criteria.

On first listen, the Linn amp may not dazzle. It doesn’t have the quintessential iron-fisted bass, searing highs, or earth-shattering dynamics. It also doesn’t pamper the listener with the uncanny kind of presence and sense of completeness one might expect from a great tube amplifier. But ignore it at your own peril.

What the Linn Klimax Twin does offer is superb definition, a lack of obvious character, and overall balance -- in spades. Those sonic characteristics not only separate the Linn amp from much of the field, but also place it among audio’s elite. I don’t know about you, but that’s more than enough for me.

...John Leosco
johnl@soundstage.com

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