The Power Of One
Sydney Morning Herald
Monday March 20, 2000
Why would anyone consider buying a single-channel (mono) power amplifier at a time when stereo has been around for more than 40 years and is now being superseded by home-theatre music systems that offer six to eight channels of sound? The answer is simple. Signal purity.
Modern home-theatre receivers contain up to eight internal amplifiers, which often share a common power supply. When one channel needs more than its fair share of power, it steals it from one or more of the other channels, which often distorts the sound they produce. Even worse is the contamination of the signal from the built-in AM/FM tuner section and the digital-to-analog converter used to decode Dolby Digital 5.1 multi-channel audio signals.
What does this interference sound like? At worst, it's similar to the distorted, garbled sounds you hear from your car radio when you drive beneath a cable TV line. At best, the sound is not distorted but the noise floor is compromised, so that when there's a break in the music you can hear background hiss. This hiss can also adversely affect low-volume music signals.
A certain way to avoid all these problems is to use a stereo amplifier, rather than a home-theatre receiver, for listening to music via CD.
Those in search of the ultimate in sound quality say there are compromises involved even in a stereo amplifier, because once again the two channels usually share the one 240V power transformer and smoothing/storage capacitors. As a result, music signals in one channel can affect the signals in the other. The only answer here is to separate the channels completely, using two separate monophonic amplifiers, usually referred to as "monoblocs".
British manufacturer Musical Fidelity is a champion of the monobloc approach to high-fidelity sound. Its most distinctive model is the tubular X-A200. Rated at 200 watts RMS, this amplifier is virtually handmade. Musical Fidelity even advises that each amplifier may run at a different temperature, due to the output transistors of each being individually adjusted to achieve optimum performance.
Noise is 120dB below signal level, so there is no audible hiss or hum in the output, and distortion is less than 0.09 per cent. Unlike many British amplifier designs, which tend to cut off high frequencies prematurely, the X-A200 will produce its full-rated output as high as 80kHz - far above the upper limit of the CD format and human hearing. On test, our two X-A200s (you need one for each channel, remember) performed perfectly. No noise was audible, even in silent spaces between CD tracks, and there was ample volume available, so this Musical Fidelity pair could, if required, easily drive any pair of loudspeakers to lease-shattering volume levels.
If you don't believe in compromise and you don't mind unusual - even eccentric - styling, a pair of X-A200s could be your ticket to improved sound.
Infofile
Musical Fidelity X-A200 Monobloc Power Amplifier
Price: $1,499
Audio Services Pty Ltd
64 Burns Bay Road, Lane Cove, NSW 2066
9427 6755
sales@lenwallisaudio.com.au
www.musical-fidelity.co.uk
© 2000 Sydney Morning Herald