Company Address: c/o Madrigal Ltd., P.O. Box 781, Middletown, Conn. 06457.
The Mark Levinson No. 23 power amplifier is a direct descendant of the No. 20 monaural power amplifier reviewed in the August 1987 issue of Audio. It is not a pure Class-A amplifier, but it does offer nearly twice the power of two No. 20s at about half the price. It's rated at 200 watts rms into 8 ohms, 400 watts into 4 ohms, and 700 watts into 2 ohms. The amplifier is very much a high-end product. At $4,700, it is certainly expensive, although in a world where a reference mono amplifier can be priced in excess of $10,000, the issue of what is really high cost is becoming more and more uncertain.
Power-amplifier technology is a difficult thing to discuss, given the number of really superb-sounding amplifiers that use radically different circuit topologies. Also, I am less and less sure that most amplifier specifications and test results are relevant to performance. Virtually every mid-fi and high end power amplifier has vanishingly low rated distortion. On this, the No. 23 certainly qualifies. Its harmonic distortion is 0.03% at 200 watts into 8 ohms, and IM distortion is 0.04%. Most amplifiers have excellent bandwidth, and the No. 23's is 4 Hz to 140 kHz. Most amplifiers have a high damping factor, and the No. 23's is over 700. As has already been mentioned, the No. 23 can deliver very high wattages, but sheer wattage also seems to be less and less important as more high end speaker manufacturers opt for complex impedances and for designs that require that an amplifier deliver large amounts of current as well as voltage. As a result, the No. 23's peak capabilities may be more important, and these are also outstanding. The No. 23 is said to deliver peak power of 3,025 watts, peak voltage of 55 V, and peak current of 55 amperes.
As for physical characteristics and circuit layout, this is a large amplifier; it measures 8 1/2 inches high, 17 1/2 inches wide, and 15 inches deep and weighs 83 pounds. Two entirely separate monaural amplifiers are housed within the same chassis. The a.c. input is filtered to remove radio-frequency interference, and a circuit corrects for any d.c. offset in the a.c. line. The No. 23 has new toroidal power transformers with a capacity of 1,200 VA each, and these feed two separate power supplies in each channel. The actual power supplies have a total of 144,000 µF of capacitance, with 36,000 µF on each rail and 36,000 µF connected to the output devices through an impressive set of copper bus bars.
The manufacturer's description of the No. 23's audio stages takes up about three pages of closely spaced type, and there are indeed a number of impressive features discussed. The No. 23 uses nothing but discrete bipolar junction devices. All of the drive stages except the output stage are pure Class-A. There are special bias, current, and regulation features in virtually every gain stage, and feedback is very carefully handled. Clipping is well controlled to minimize audible distortion, and the output stages have ample reserve to handle the power required. There are optional balanced inputs, and exceptional protection is provided with minimal interference with the signal.
If you want all the technical details concerning this amp, I suggest you contact a dealer or write to the manufacturer. All I can really say in this space is that the design of the No. 23 reflects a strong effort by a team of engineers who very clearly know both electronics and how to listen. Accordingly, it is yet another demonstration that no one approach to circuit design is as important as the experience and skill that go into a given design approach.
The Mark Levinson No. 23 is an interesting challenge to anyone who believes that all amplifiers sound alike. To start with, it is far more dynamic than most amplifiers with the same power rating, and this is particularly apparent with the difficult loads imposed by many of today's best high-end speakers. This superiority in dynamics may not seem important until you hear the difference. Many systems, even high end ones, tend to have a "polite" sound. They veil the excitement in musical dynamics, and many sacrifice bass depth and power and harden the upper midrange when confronted with sudden loud passages.
Unlike amplifiers with weak or trick power supplies, the No. 23 opens up the sound of virtually all prerecorded music without any loss of transparency. This is as important in simple music as in large-scale symphonic or rock music. It is immediately apparent with a good harpsichord recording and in rapid soprano vocal changes. It improves percussion and such sounds as the bowing of a stringed instrument.
Equally important, the No. 23 has the combination of power and stability to drive virtually any speaker system to its best. I have heard 300-watt mono amplifiers that had trouble, for instance, with the Infinity 9 Kappa, but the No. 23 takes it easily in stride. It performs superbly with the Apogee Duetta and with some hand-built ribbon and electrostatic speakers whose characters I have heard sharply altered by other amplifiers.
Further, the No. 23 delivers its power without any sacrifice of clarity at low listening levels. As little as two years ago, even the best high-end transistor amplifiers had a tendency to emphasize and harden the upper midrange In the case of very high-power amplifiers, there was an additional tendency to veil or color all music at low levels and to allow medium- and high-level passages to sound their best. As a result, there was a clear trade-off between low-power amplifiers, which were optimized for sweetness and transparency, and high-power amplifiers, which stressed power. These problems also led to a great deal of debate in the high end over tube versus transistor and Class A versus Class AB. Well, there are still differences among amplifiers. The Mark Levinson No. 20, the Krell Class-A amplifiers, hybrids like the Audio Research M300, and pure tube designs like the OTL Counterpoint SA-4 do provide a slightly sweeter and more detailed upper midrange and treble than does the No. 23. I cannot say, however, that the margin of difference is going to be important to anyone but the most demanding audiophile. Besides, all of those models are more expensive than the No. 23. By every other standard, the No. 23 shows that a Class-AB transistor amplifier can provide all the power needed to deliver the deepest and loudest bass passages with all the musical sweetness that anyone could possibly desire.
As for the sound stage, it is difficult with an amplifier of this caliber to distinguish between the inherent quality of the amplifier and that resulting from the amplifier/speaker interface. This is, however, an unusually three-dimensional power amplifier, surpassed only by the larger conrad-johnson tube amplifiers and a handful of ultra-expensive reference transistor designs. The sound-stage width is excellent, and imaging is very good. Unlike some of the older Mark Levinson amplifiers, there is no hardening of the sound, which can make an amp's character slightly forward and two-dimensional; the No. 23 clearly outperforms the last generation of Mark Levinson Class-A amplifiers in this regard.
The pleasures of an amplifier like the Mark Levinson No. 23 only really become clear after prolonged listening to a wide range of music on a top-quality system, one that includes speakers good enough to demonstrate its merits. The No. 23 is one of the best reference amplifiers around. Unlike many other expensive, high-end amplifiers, it is relatively universal in character, and its sonic trade-offs are well chosen to fit into virtually any system. It is scarcely cheap, but it also is the kind of amplifier you can use for years longer than many competing units.
Equally important, the No. 23 reveals the kind of unique sonic character that deserves high praise. There may be some who feel that this amplifier sounds like its less costly counterparts that have similar specifications. Perhaps they are the same people who believe that all wines taste alike, and all cars drive the same way.
--Anthony H. Cordesman
(Source: Audio magazine, Apr. 1988)
Also see: Mark Levinson No.26 Dual Monaural Preamp (Aug. 1989)
Mark Levinson No.20 Mono Amp (Aug. 1987)
Mark Levinson: The Shape of Things to Come (Advertisement, April 1988)
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