by Bert Whyte
IT’S THAT TIME of year again--autumn in New York--and the 46th Audio Engineering Society convention begins its four-day run at the prestigious Waldorf-Astoria. With the general upswing in the recording business, this has encouraged more and more equipment manufacturers to take exhibit space at the convention, so there will be scads of interesting new audio items, which we will report to you in due time.
Time is indeed a problem in dealing with audio products. Far too often a product is announced, or a prototype shown, and by the time you get a unit for evaluation, a year may have passed.
As a matter of incidental interest, you may not be aware that electronics manufacturers are currently in a terrible bind for parts. It seems that during the recent recession most parts vendors let their inventory position diminish almost to the vanishing point. Now that things are booming again, the lead time on items such as power transistors, resistors, capacitors, etc. has assumed incredible proportions. You hear horror stories such as 40 weeks for "garden variety" parts, and a year or more wait for specialty items. One manufacturer of high-power amplifiers requires a very fancy capacitor and the vendor of the part is quoting a mere 2 1/2 years delivery! Needless to say, a great deal of intricate "wheeling and dealing" is going on in efforts to circumvent these situations. It is also obvious that the small, highly specialized audio manufacturer, who is usually in a limited capital position, is particularly vulnerable in this parts bind. In spite of all this, most companies seem able to cope with the situation. Fortunately too, the traditionally "venturesome" audio manufacturer has continued his research programs and we see the fruits of all this labor at the engineering conventions. It also appears that the parts shortage has not deterred "people with ideas," from entering the audio business. A case in point is the story of Mark Levinson Audio Systems, a Connecticut-based manufacturer of some very exotic audio products.
I first encountered the company at the 45th AES convention in Los Angeles last May. Sharing a demonstration room with Burwen Laboratories, they were showing their LNP-2 preamplifier which drew attention not only because of its unusual design, but for the rather dazzling specifications which were quoted and the rather breath-taking price of $1750.00! As is usually the case, a brief exposure in a typical demonstration room gives a very superficial evaluation of a product, but what I saw and heard of this preamp intrigued me. I made arrangements to try out one of these units, and for the past several months it has been in daily use in my audio system at home.
Mark Levinson is a very intense, dedicated young engineer, who is by far the most rigidly uncompromising audio purist I have ever met. His company philosophy and his products are a reflection of this attitude. As I have gently pointed out to him, "his way" is not the way to riches. His disdain of component parts that are not of "state of the art" quality is almost monumental. His immaculately wired preamp uses Teflon-coated, shielded wire throughout, and one engineer friend of mine saw this, snorted, and said "Hell's Bells! Who needs it? This is aerospace stuff!" Mebbe so . . . but this practice yields crosstalk of minus 95 dB and relative immunity to noise pick-up.
As you can see in the photo of the unit, it is designed for rack-mounting. The chassis is brushed black anodized, and top and bottom plates are secured with stainless steel Allen screws. All lettering and index markings on the front panel are hand-engraved. The satin-finished aluminum knobs are large and easy to handle. The LNP-2 preamp is a modular unit. The military spec, glass-printed mother circuit board has gold-plated input sockets. These mate with six Burwen plug-in epoxy encapsulated UM201 mixing amplifier modules, which are high gain 7mc bandwidth operational amplifiers of extremely low noise . . . 1 microvolt 20Hz to 20kHz. A seventh plug-in module is a Burwen VU306 peak VU detector. There is an eighth input socket which will accept other optional special function modules. As you can see, there are two large Weston VU meters and the meter function is controlled by the VU306 peak detector. Normal VU averaging characteristics are provided in one switch position.
In another position, the module gives a 5 microsecond response and will hold peaks for 2 seconds. The switch position marked HF + shows + 13 dB @ 20kHz for slow speed tapes to avoid high frequency saturation. The meters monitor the record output of the unit. The preamp has input provisions for phono, tuner, auxiliary and two tape units.
Main output and two tape outputs are provided. Cannon connectors are in parallel with standard phono connectors for tape in and out and amplifier output.
Mark uses a regulated plug-in epoxy encapsulated power supply mounted in a separate chassis to avoid hum pick-up. The unit has the usual input facility switches and mode switches.
In addition it has input level controls, which are in essence balance controls, and record output switch so tapes can be made either in mono or stereo. Zero VU levels can be adjusted by a pre-set 700 Hz sine wave calibration tone. On the top right of the preamp is a 0-40 dB gain control switchable in 10 dB steps to allow maximum S/N ratio for any input level. There are three tone controls: 20Hz, + 14 to -8dB in 2dB steps; 5kHz, +3 to -3dB in 1dB steps; and 20kHz, + 14 to-8dB in 2dB steps. Noise with these controls is typically less than 100 dBm (all controls maximum, less than minus 87 dBm.) Throughout the preamp, resistors are 1% tolerance metal film. Capacitors are either solid tantalum or 1% tolerance metallized polycarbonate. Potentiometers have conductive plastic elements and Teflon-coated shafts. The input level controls and the ganged volume control are calibrated in 1 dB steps from 0 to -30dB and are guaranteed to track within 0.1 dB between channels for virtually identical frequency response and amplitude. On the rear of the preamp is a Cannon connection which is for powering a versatile electronic 'crossover, which is just about to achieve production status.
For those die-hard advocates of moving coil phono cartridges such as the Ortofon, which have problems with low output, Mark has the JC-1 pre-preamp, a John Curl-design six years in the making, to solve the gain problem with an astounding equivalent input noise of -147 dBm.
As I noted earlier, the specifications on this Mark Levinson preamp were so spectacular, that I wanted a thorough check-out on them. Thus, I had some tests run at a very sophisticated manufacturing facility, where among other things they had a Hewlett-Packard Fourier harmonic spectrum analyzer.
On the line inputs to main or record output, the tracing on the graph was practically unwavering showing harmonic distortion below 0.001, and this at odd and even harmonics way on out.
The same test on the phono input showed some 0.003 to 0.004 spikes at odd harmonics, but we later learned this test was invalid because the input gain control was set at the 40 dB point, a setting that would almost never be used in any normal circumstances. I next visited the Mark Levinson labs in Connecticut and ran through every test with Mark. He has fine equipment including the well-known Radford low-distortion signal generator, Hewlett-Packard voltmeter and digital voltmeter, scopes, etc.
We checked every standard parameter, and all met or exceeded the claimed specifications. Thus the tracking between pots was verified at 0.1 dB. The frequency response bettered the listed ± 3 dB, 0.5 Hz to .5 MHz and 0.1 dB, 5 Hz to 100 kHz. THD was less than 0.005%, d.c. to 10 kHz, 0.02 at 20 kHz. S/N ratio of the phono measured a fabulous 86 dB below 10 millivolts input at 1 kHz (inputs shorted), and the line measured an incredible minus 134 dB! The RIAA curve was accurate to within 0.4 dB from 20 Hz to 15 kHz. Phono overload was at the lofty figure of 250 millivolts, better by at least 50 millivolts than any other preamp I am familiar with.
Okay ... so everything checked out with this super unit. The big questions are ... is any preamp worth this kind of money . . . and what did it sound like? Can any difference be detected between this unit and the lesser-priced preamps on the market? As far as money is concerned, this is a preamp designed to be used as a laboratory tool; it is a professional instrument in the truest sense of that overworked word. The unit is guaranteed for 5 years, parts and labor free of charge. If your inclinations are to superb specs with maximum repeatability and reliability and your pocketbook can absorb the shock, it certainly can be regarded as an investment. As to the sound, it does one thing superbly well ... phono and line noise simply are inaudible and cease to be a factor.
It sounds measurably cleaner in the phono listening, perhaps because of the high overload characteristics and the high velocities encountered on today's discs. The transient response is razor sharp in line or phono, and the bass is unusually solid and clean. Yes, there are audible differences, subtle to be true, and admittedly something you have to listen for, but if you are one of the purist-elite to which such subtleties are important this preamp is unquestionably . . . monetary considerations aside ... the premier choice.
(Audio magazine, Nov. 1973; Bert Whyte)
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