Wayne Donnelly - Audio Tweak

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.