Mark Levinson ML-6B (1980s)
The ML-6B is the final and most refined version of Mark Levinson's flagship ML-6 preamplifier, introduced in 1980 and designed by chief engineer Tom Colangelo. The "B" revision added FET transistor upgrades over the original ML-6. One period source calls it simply "a slightly modified version" of the ML-6, while another calls it "the updated version." Either way, it ended the ML-6 series before the more affordable ML-7 and ML-10 followed.
The design was uncompromising. The signal path was fully discrete and DC-coupled, with no integrated circuits and no coupling capacitors in the audio path. Each channel was completely separate and had its own power supply, a dual-mono layout that eliminated cross-channel interference. The phono stage was highly modular, with gain and loading adjustable by the user through internal settings. Sources differ on whether the ML-6B offered both moving coil and moving magnet configurations or was fixed to one version. The rear panel had both balanced XLR and single-ended RCA inputs and outputs.
The historical record is muddy on the power supply. According to the service manual, the unit comes with a separate outboard power supply, and the design puts it in its own chassis to keep vibration and electromagnetic interference away from the audio circuits. Some owner sources, however, describe the ML-6 as built on a single heavy dual-mono chassis. This may reflect a physical redesign across the ML-6 / ML-6A / ML-6B sequence, and the ML-6A is sometimes credited with introducing the separate supply. The sources don't agree, and the exact timeline is not documented.
Reviewers and owners do agree on the sound. The Absolute Sound's contemporary review called it "the most musically satisfying preamplifier" they had heard to that point. Owners consistently describe a "quiet, black background" and exceptional transparency. Many say the phono stage matches or beats outboard phono preamps costing as much as the entire preamp. The original retail price in 1980 was approximately $2,800 - $3,200, and the ML-6B later sold for around $4,000+ by the mid-1980s.
Known specifications from the service manual, as reported in modernclassic.co.uk and related period listings:
- Gain: 48 dB (amplifier sections) per the service manual; −23 dB (buffer sections). A contemporary review cited 38 dB, which may refer to a different stage or to overall gain.
- Distortion: less than 0.1% at any level per the service manual. The Absolute Sound review published no THD rating, since it did not consider distortion a meaningful measurable differentiator in that context.
- Power consumption: 40 watts
- Power requirements: 105–125 VAC, 50/60 Hz
- Inputs: Phono (MC/MM), high level/tuner, auxiliary
- Outputs: Main and tape
Notes for owners: the push-button power switch is prone to failure, the original electrolytic capacitors will need replacing after three decades, and the original Toshiba FETs are now obsolete and very hard to source. Recapping is the single most-recommended procedure for restoring a unit to original spec. Current market listings for ML-6 series units run from roughly $2,500 to $6,500, depending on condition, version, and whether original packaging is included.
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