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March 2006
Digital power amplification has been around for quite a while, and recently a number of new marques have hit the marketplace, typically offering higher power output per dollar than traditional solid-state and tube amplifiers. This writer has not yet had a chance to listen carefully to any of those 'Class D' newbies, but for the last three months I have been having loads o' fun with the latest offering from a grizzled veteran of the digital amplifier wars, Spectron Audio.
The 500 watts-per-channel (into 8 ohms) Musician III occupies a modest-sized chassis about the size of a typical 100 wpc solid-state amplifier. But don't be fooled. This thing is capable of brutal power into low-impedance loads that could defeat or even destroy many power amplifiers. Output into 4 ohms is listed conservatively as 700 continuous wpc, and John Ulrick informs me that the amplifier can deliver a sustained1,400 wpc into a 0.5-ohm load. It is difficult to conceive of any home loudspeaker that the Musician III could not comfortably drive to thunderous volumes. And, not surprisingly, Spectron OEMs the power modules used in the Musician III for use in pro sound applications where very high power and bulletproof reliability are essential.
Technical Highlights Closed loop with fast response time: Feedback corrects for errors in the output. In amplifiers with transformer output or slow analog circuitry, application of fast, high-performance feedback loop correction is less than optimal. In Spectron amplifiers the feedback loops are about ten times faster than in conventional amplifies. Spectron asserts that this ultra-fast correction makes its amplifiers superior at capturing fine details in the music signal. Isolated low-level power supplies: Over the years, some preamplifier designers have gone so far as to use batteries to achieve isolation from the AC mains. To achieve the same effect, Spectron employs a micro-sized switching supply for the +15V that operate the low-level amplifier and the digital logic. This design is about 500 times more isolated than the conventional method of taking power from a 50/60Hz transformer. As a result, the new Spectron amplifiers are far less in need of power conditioning or premium power cords in order to sound their best. Floating RCA inputs: Ground loops have always been a problem in audio. They may show up as obvious buzz from speakers with no music playing, or as more insidious hum that rises with increasing loudness. Even when masked by the music, this hum can make music sound less natural and detailed. The Musician III's balanced XLR inputs are not susceptible to ground loops. When connected via single-ended interconnects, the Musician III's floating RCA inputs eliminate ground loop buzz and hum. Power capacitors: To store energy between each cycle of power from the 50/60 Hz power lines, all amplifiers use energy-storage capacitors. Most amplifiers have one big capacitor for the + supply and a second for the - supply. The Musician III uses separate banks of capacitors for the left and right channels, emulating a dual mono topology. Those banks of small capacitors provide a lower-impedance supply to each amplifier module than one big capacitor can achieve. High-output voltage and current: A power amplifier's ability to drive loudspeakers is based on its supplying ample voltage and current. When the amplifier runs out of voltage, it voltage clips; when it runs out of current, it current clips. With the Musician III's very high peak voltage of 110 volts and peak current of 50 amps, neither voltage nor current clipping is likely in a home music system. Despite numerous excursions into unwisely loud listening levels during the review period, I was never able to push the Musician III into audible clipping.
In addition to the preceding highlights, there are a couple of other features that distinguish the Musician III from most other power amplifiers. Any audiophile who has ever shorted out a big amplifier knows what a heart- sickening phenomenon it is — likely to involve loud pops, electrical flashes and smoke, followed by deadly silence and lingering bad smells. The Musician III is blessedly immune to such destructive blowups — a comforting thought when running such high power into your precious loudspeakers. With the fold-back current limiting implemented in the Musician III, if the amplifier is overdriven to the 50-Amp peak current limit, it will continue to deliver 50 Amps for half a second. It then automatically reduces the output current to 15 Amps over the next half second, and maintains the 15 Amps until the load returns to normal. The practical effect is that shorting out the Musician III won't hurt it. And if you have "amp-killer" speakers — like the infamous Infinity Kapa 9s, which go below one-ohm impedance — you can play them loudly, and you probably won't even hear when the current limit kicks in. The Musician III won't just shut down at too-high current levels as other amplifiers do. Unique to Spectron is the Remote Sense speaker cable system, which is designed to eliminate sonic degradations caused by the musical signal passing through various types of loudspeaker cables. For $595/pair, Spectron supplies special four-conductor cables; two conductors carry the musical signal, while the other two feed back to the amplifier output terminals. They connect to the amplifier via twist-to-connect SpeakON connectors. The concept here is to extend the amplifier's global feedback network in order to correct signal errors all the way out to the end of the speaker cables — in contrast to all other amplifiers, whose control of the signal ends at the cable. Unfortunately, I was unable to thoroughly evaluate this feature in time for this review. I will publish a follow-up in the near future to address the comparative performances of Remote Sense versus conventional premium loudspeaker cables. In addition to all of the features described above, the Musician III incorporates fault sensing (of excessive DC or high-frequency output) protection and reset, over/under voltage protection, and thermal shutoff and recovery. In short, the brute power of this amplifier is well fortified against virtually any possible malfunction.
Exterior Tour
Review Setup The Musician III has been auditioned for three months in my reference rig: VTL 7.5 line preamplifier, Modwright/Denon 3910 all-format player (review coming), Thor TA-3000 Mk II phono stage, Basis 2800 vacuum turntable, Graham 2.2 arm/Transfiguration Temper cartridge, mostly Bybee cables. For the first couple of weeks I listened to Meadowlark Blue Heron 2 loudspeakers; after that, the Analysis Omega planar/ribbon loudspeakers (also reviewed in this issue.)
Listening The Musician III from the beginning exhibited a very wideband, high-speed musical presentation. That in itself was no surprise. What is surprising is, first, that it sounds more extended in the high frequencies than any amplifier I have had in this system, solid-state or tube. And secondly, that extraordinary treble extension is remarkably free of the tonal brightness, the glare and grain that have marked my listening experiences with so many transistor amps over the years. The neutrality was so pronounced that it took me a few days to become accustomed to it. And as the amplifier burned in, that extended but smooth and relaxed quality grew even more natural sounding. The highs took on a lovely, crystalline quality, somehow unlike other amplifiers I can recall. Perhaps the closest comparison I can think of for this degree of tonal purity is with the 55 watt WAVAC MD-805 monblocks I reviewed last November. I expected very deep and powerful bass, and half-expected it to be the kind of "slam" I associate with Krell and a few other marques (and which I tend to find exaggerated). In fact, the bass of the Musician III has a full measure of low-frequency depth, speed and pitch definition. Equally as important for me, its scaling of dynamics seems flawlessly accurate, from bass drum thwack to the triangle's strike and decay, and everything in between. As I mentioned at the beginning, this is my first review to be based entirely on listening in my new Chicago music room, which is clearly superior to the room I used for the past 15 years in California. That factor notwithstanding, I feel confident stating that the spatial resolution of the Musician III is outstanding. Playing the finale of Mahler's Resurrection Symphony (Michael Tilson Thomas leading the San Francisco Symphony, soloists and Chorus), the spatial organization of these gigantic performing forces is more clearly delineated than ever before. Yes, the chorus are obviously ranged behind and surrounding the instruments. But the depth of the soundscape is greater than I have heard before on this very familiar recording. In addition, the placement of individual players — solo oboe firmly in the middle of the orchestra, trumpets clearly at the rear; soprano and mezzo soloists clearly separated from the chorus, even when they are all singing together — is uncannily precise. It's as if my listening room has morphed into Davies Symphony Hall right in front of me. As I play more and more familiar recordings, I am stunned by how faithfully the ambiance of each recording venue is captured. I can easily distinguish between closely and distantly recorded piano, between jazz in a club versus a larger venue. And so forth...
Summing Up A couple of years back, I most enthusiastically reviewed the massive John Curl-designed Parasound Halo JC-1 400-watt monoblocks, which I have since regarded as the best solid-state amplifiers I have experienced. At $6,000 per pair, they seemed to me a great bargain. Now, after the lapse of time since that review, I cannot say authoritatively that the Musician III sounds even better, but I think it very likely does. At the least it's a close call. And I have no qualms about pronouncing the Musician III a tremendous value. Anyone looking for powerful yet highly refined amplification would be foolish to ignore the Spectron Musician III. I believe it will serve me well as a standard against which to measure other amplifiers. So I'm keeping this one. Superior audio indeed!
Specifications Frequency Response: 20Hz to 20kHz ( ±.1dB) at 8 Ohms Power: 4 Ohms 700 wpc, 8 Ohms 550 wpc, and 1,400 wpc at 2 Ohms Maximum Output Current: 50 Amps peak Max Output Voltage: 110V Damping Ratio: 400:1 Distortion, THD: <.06 percent at 500 watts into 8 ohms Noise: <83dB Inputs RCA: Gain = 26dB, 50K ohms impedance XLR: Gain = 28dB, 25K ohms impedance each side of center tap (true balanced) Dimensions: 19 x 5.25 x 13.5 (WxHxD) Weight: 48 lbs. Warranty: 3 years Price: $4,995
Company Information Voice: (818) 727-7603
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Spectron Audio Musician III
Few if any audio designers can match the engineering
experience and credentials of John Ulrick, Spectron's founder, chief
designer and CEO. Ulrick co-founded (with Arnie Nudell) Infinity back in
1968, and designed the digital servo-amplified subwoofer that launched
that company. He designed the first Class D amplifier in 1974. His latest
offering, the Musician III, presents a formidable challenge not only to
other Class D contenders, but also to top-rank power amplifiers of every
type.
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