Audio Research LS27 Tube Preamplifier

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Absolutely mint and complete - with very few hours of use.

Comes with the original remote, double box, manual and all packing materials.

Click here for a PDF copy of the Audio Research LS27 Owner's Manual

Retail new was $7,000.

Audio Research says it best on this preamp:

The LS27 is our finest LS-series preamp ever, replacing the venerable LS26 after almost five years. Benefiting from the latest developments in our Reference series, the LS27 distances itself from the competition by offering a level of performance not previously obtainable in its price range.

The LS27 not only offers remarkable resolution, musicality and dynamic impact, it is our most flexible line-stage and able to adapt to most any situation. In terms of control options, the LS27 has selectable High / Medium / Low gain settings for each input, BAL / SE input selection, Left-Right Balance control, Invert (phase), and Stereo / Mono selection.

Tube hours can be monitored, there is a Processor pass-through for home theater applications, and the display is dimmable with the option of being turned off. All of the inputs and outputs have balanced XLR and single-ended RCA connectors, including six pairs of discrete inputs, a processor (unity gain) input, a monitor loop, and two sets of main outputs. A new microprocessor controls all functions. The rear panel also includes a 12V trigger and a 15A IEC connector.

The LS27 is a pure Class-A design with zero feedback, and the massive power supply is fully regulated. Gain is provided by twin 6H30 triodes. Multiple circuit changes and refinements account for greatly improved performance, including bulk power-supply storage that has been substantially increased, a new power transformer, and costly new output and bypass coupling capacitors that bring new dynamic life and even more refinement to the presentation.

The LS27 sounds very much like a REF5 on a slightly smaller scale, with an organic, lifelike musicality. Like its big brother, the LS27 combines great resolving power with a tonal richness, purity and naturalness that is immediately involving. The grain structure is superfine and electronic artifacts have been banished. Bass impact and control are also superb, and we believe that the LS27 surpasses the performance of the REF3 in virtually every way, making it a stunning value.

Look inside the LS27 to see the exceptional workmanship of this hand-made product. Hear it in your system to appreciate everything that went into the design and production of this compelling new preamp.

Specifications:
FREQUENCY RESPONSE: +0-3dB, 0.2Hz to 160kHz at rated output (Balanced, 200k ohms load)

DISTORTION: Less than .01% at 2V RMS BAL output.

GAIN: Main output: Selectable for each input: 24dB, 18dB,
12dB Balanced output. (18dB, 12dB, 6dB SE output.)
Record output: 0dB (Processor input: 0dB balanced).

INPUT IMPEDANCE: 120K ohms Balanced, 60K ohms SE. Inputs (8): Tuner, Phono, CD, Video, Aux 1, Aux 2, Moni- tor, Processor (XLR and RCA connectors).

OUTPUT IMPEDANCE: 700 ohms Balanced, 350 ohms SE Main (2), 20K ohms minimum load and 2000pF maximum capacitance. Outputs (3): 2 Main, 1 Record (XLR and RCA connectors ).

OUTPUT POLARITY: Non-inverting.

MAXIMUM INPUT: Low Gain: 48V RMS BAL, 24V RMS SE, Medium Gain: 24V RMS BAL, 12V RMS SE, High Gain: 12V RMS BAL, 6V RMS SE.

RATED OUTPUTS: 2V RMS 1Hz to 100kHz into 200K ohm balanced load (maximum balanced output capability is 15V RMS at less than 0.5% THD at 1kHz).

CONTROLS: Rotary volume selector (104 steps) and rotary input selector.
Push buttons: Power, Mono, BAL / SE, Proc, Monitor, Mute. Also remote buttons: Display, Bal L, Bal R, Hours, Invert, Gain.

POWER SUPPLIES: Electronically-regulated low and high voltage supplies. Automatic 50 sec. warm-up/brown-out mute. Line regulation better than .01%.

NOISE: 1.3uV RMS residual IHF weighted balanced equivalent input noise with volume at 1 (100dB below 2V RMS output).

TUBE COMPLEMENT: 2-6H30P dual triode, (Hybrid JFET/ tube audio circuit, solid-state power supply.)

POWER REQUIREMENTS: 105-130VAC 60Hz (210- 260VAC 50/60Hz) 50 watts maximum.

DIMENSIONS: 19" (48 cm) W x 5.25" (13.4 cm) H (standard rack panel) x 13.3" (33.8 cm) D. Handles extend 1.50" (3.8 cm) forward of the front panel.

WEIGHT: 16.3 lbs. (7.4 kg) Net; 23 lbs. (10.5 kg) Shipping.

Our Testing Process for Preamplifiers at SkyFi:

We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and transistors are checked for signs of stress or damage. Special attention is paid to the power supply which is the most common source of failure for preamps. We then power up the unit and run a simple 1k sine wave while monitoring the low voltage output on an oscilloscope for signs of distortion or noise to get a baseline.

At this point we will lubricate and clean all switches and potentiometers (that are not sealed) with a high quality contact cleaner, and then re-test all functions for any signs of noise or scratching.

Final testing involves putting actual music through the preamplifier We have learned over time that some issues are only noticeable to a trained ear while listening to a familiar source material. Our test bench has reference vintage Kef speakers that we are super familiar with which will quickly reveal any discrepancies. Some preamps will then move into the listening room where they will be tested with our in-house reference system.

Please click here for detailed specifics regarding our specialized packing process that separates us from the rest.