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If you re surprised to learn that tubes solve some amplifier problems best, you have something to learn about amplifiers. And about LUX. It may seem courageously retrogressive for a company to introduce a tube amplifier-even a highly advanced type-to the semiconductor audio world of 1976. Especially for a company only recently established in the U.S. market with a comprehensive line of solid-state amplifiers and tuners. But for LUX, it is simply consistent with our philosophy: whatever path may lead to improvement in the accuracy of music reproduction will be explored by our audiophile/ engineers. Whether it leads to transistors or tubes. Certainly, transistors are not about to be obsoleted by tubes. However, there are some amplifier problems that tubes still handle better than transistors. Overloading is one such problem. When a solid-state amplifier is driven beyond its rated power, it clips abruptly. Engineers call it "hard" clipping. The term is apt, as the sound from the spurious high-order odd harmonics is raspy and irritating. Further, if the overall circuitry is not stable, and the protective circuits not very well-designed, the distortion is extended in time beyond the moment of overload. Drive a tube amplifier beyond its rated power and it too clips the waveform, but gently and smoothly. This "soft" clipping introduces much smaller amounts of odd harmonics. The distortion is far less irritating, hence less noticeable. Notch (or crossover) distortion, present in many transistor amplifiers, is another source of spurious high-order odd harmonics. It occurs when the transistor output circuits are notable to follow the musical waveform accurately at the points where it changes from positive to negative and back again. Since notch distortion, unlike clipping, is at a constant level regardless of the power the amplifier is delivering, the ratio of this distortion to signal is worse at lower power. The gritty quality heard from many transistor amplifiers, particularly when they are playing at low levels, is usually due to crossover distortion. Of course, tubes also have their limitations. Especially conventional tubes. The only tube previously capable of high-power amplification-the pentode-has inherently higher levels of distortion than the triode. Existing lower-distortion triode tubes cannot deliver sufficiently high power as a simple push-pull pair But LUX, together with NEC engineers, has developed the first of a new breed of triode tube, the 8045G, which with other related technological advances, makes possible a high-power, low-distortion triode amplifier-the Luxman MB-3045. Among the differences in this new triode: the plate-electrode uses a special bonded metal with high heat-radiation characteristics. Also, the tin structure further aids heat dissipation. LUX also developed a low-distortion high-voltage driver tube, the 62400, capable of delivering over 200 volts of audio signal to the output triodes. Also, a new output transformer (LUX's,long-time special area of expertise) has been designed to take optimal advantage of the triode configuration feeding it. The quadrafilar winding and core technology of this transformer represents another break through. Overall, from input to output, the use of advanced design direct-coupled and self-balancing differential amplifier stages ensures stability and minimum phase shift. The MB-3045 produces a minimum of 50 watts continuous power into 4, 8, or 16 ohms, at any frequency from 20 to 20,000 Hz, with total harmonic distortion no more than 0.3%. As the MB-3045 is monophonic, a pair of them connected to a stereophonic preamplifier will not be subject to stereo power-supply interaction. Now, we don't expect the MB-3045 to become the world's best-selling amplifier, any more than our highest- power solid state power amplifier, the M-6000 priced at nearly $3000. You'll find both at our carefully selected LUX dealers who will be pleased to demonstrate them for you. And any of the other dozen or so LUX models. It's why they're LUX dealers in the first place. When a typical transistorized amplifier tries to deliver more power than it can. the top and bottom edges of the waveform "clip" sharply and abruptly ..and not always sym metrically Result high-order harmonic distortion. raspy and irritating. When a tube amplifier. such as the Luxman MB-3045. is driven into over load, the "clip ping- is softer. with more rounded edges to the waveform. The resulting distortion is much less audibly bothersome. Luxman MB-3045 monophonic tube power amplifier. 50 watts minimum continuous power into 4, 8, or 16 ohms, 20-20 kHz: total harmonic distortion no more than 0.3%. Frequency response: 10 to 40 kHz, ± 1 dB. Signal to noise ratio: 95 dB. Variable sensitivity, control for matching gain to any preamplifier. $445.00 each. Luxman CL-35 III stereo tube preamplifier. Total harmonic distortion: 0.06% at 2.0 V, 20-20 kHz, all output signals. Frequency response: 2-80 kHz. +0-0.5 dB. RIAA equalization:-±0.3 dB. Features include: tape monitoring and dubbing. 6 selectable turnover frequencies, twin high and low noise filters. switchable phono-input impedance (30, 50, 100 k-ohms), variable input sensitivities. $745.00. ++++++++++++ Also see: TIME-LIFE RECORDS--The Definitive Beethoven Collection Source: Stereo Review (USA magazine) |
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