Audio Research SP-11 Legendary Hybrid Tube Preamp, Dual Chassis with Phono

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This legendary preamp requires no introduction among vintage audiophiles.

It represented the state of the art in tube preamps, and was also the flagship model from Audio Research circa 1985.

Many manufacturers have tried to surpass this performance and musicality in the past 40 years with little improvement.

Best of all it contains a very capable phono stage, eliminating the need for an additional box.

This is survivor piece in very good original condition that was fully sorted out by our in-house tube specialist.

Tube Notes:
This unit has a complement of Six (6) Audio Research branded 6DJ8 tubes. They all tested strong, and with good balance, on our modern and professional Amplitrex AT1000 Tube Tester.

Some printed flyers and original reviews included as shown in our last photo.

The SkyFi Testing Process for Preamplifiers:
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.

Audio Research SP-11 - Owner's Manual

Specifications:
FREQUENCY RESPONSE
High level input: ±1dB 0.2Hz to 100kHz. -3dB below 0.1Hz and above 200kHz. Phono input: ±.2dB of RIAA 20Hz to 40kHz. ±1dB of RIAA 1.0Hz to 100kHz.

DISTORTION (THD)
Harmonic distortion: Less than .005% at 2V RMS output, 5Hz to 20kHz (Typically less than .001% at midband, phono or line input). Intermodulation distortion: Less than .003% at 2V RMS output

NOISE & HUM
IHF weighted, shorted input: Output (Gain down): 6µV (110dB below rated output). Input (High level): 3µV equivalent input (110dB below 1V input). Phono: 0.15µV equivalent input (76dB below 1mV input)

GAIN
At 1kHz, bypass mode: Phono input to tape output: 46dB (0.2V output from 1mV input). Phono input to main output: 75dB (0.175mV input for 1V output). High level input to main output: 29dB (36mV input for 1V output).

INPUT IMPEDANCE
Phono: Front panel selectable 47K, 100, 30, 10, 3 ohms. Phono input capacitance: 150 pF at 10kHz. High level: 20K ohms or higher, depending on switch functions.

OUTPUT IMPEDANCE
250 ohms main, direct, inverted outputs. 500 ohms tape output. Recommended load 60K ohms and 100pF (20Kohms minimum, 1000pF maximum)

OUTPUT POLARITY
Tape outputs, direct output: Non-inverting. Invert output: Inverting. Main outputs (2): Selectable non-inverting or inverting. All outputs may be used simultaneously.

MAXIMUM INPUTS
Phono: 350 mV RMS at 1kHz, 1200 mV RMS at 10kHz (0.1 second maximum duration, 6dB less if continuous). High level: 25V RMS.

RATED OUTPUTS
2V RMS 1Hz to 100kHz main, direct, inverted outputs. (Maximum 80V RMS at 0.2% THD at 1kHz into 60kOhm load with 2.85V RMS high level input).

TUBE COMPLEMENT
(6) 6DJ8/ECC88

POWER REQUIREMENTS
95-135VAC 60Hz, 190-270VAC 50/60Hz, 130 Watts maximum

OTHER
Filter: 25Hz Hi-pass phono subsonic 6dB/octave rolloff (to eliminate ringing) with transition to 12dB/octave at 10Hz. Front panel switchable phono only. Controls (6): Gain, Level (to set gain range), Balance, Mode, Input, Impedance. Switches (8): Tape monitor, Copy, Tape 1/2, Tape 1to2 / 2to1, Mute, Invert phase, Bypass, Filter.

DIMENSIONS
(Each chassis, EIA Rack panel mounting) 19" (48 cm) W x 5 ¼" (13.4 cm) H x 10 ¼" (26 cm) D. Handles extend 1 ⅝" (4.1 cm) forward of panel. Interconnect cable extends 4" behind rear of chassis.

WEIGHT
SP-11: 14 lbs. (6.4 kg) Net, 23 lbs. (10.5 kg) Shipping.
SP-11PS: 15 lbs. (6.8 kg) Net, 23 lbs. (10.5 kg) Shipping.
Total: 29 lbs. (13.2 kg) Net, 46 lbs. (21.0 kg) Shipping.

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