Audio Research LS-15 Stereo Preamplifier
This is an unmodified Audio Research LS15 Line Level Preamp. This model was released in 1996 as an all new design that replaced the LS2B Mk II. Its basic makeup is an all-tube gain using four 6922 twin triode tubes, and it incorporates a fully differential, zero feedback balanced circuit with electronically regulated high and low-voltage power supplies. The Audio Research LS15 is a fully balanced preamp which gives single ended connection flexibility but has considerable sonic advantages when run in the balanced mode.
The LS 15 has an on-board microprocessor that controls a 70-step electronic relay attenuator (volume control) and a 5-position input selector. It has a large array of input and output options which include balanced inputs as well as direct balanced inputs for best signal purity. It has five single ended output options for optimal flexibility. It has two sets of balanced outputs and two sets of single ended outputs including a dedicated tape out. A removable power cord also allows for the ability to experiment with finer power cords. The LS15 comes standard with a factory set 12dB of gain, which is somewhat lower than that of its predecessor, giving a wider range of adjustment in the volume control.
The front panel has the traditional solid and simple Audio Research industrial look, and like many AR preamps of the past, it has a 5.25-inch high faceplate with the vertical black handles on the left and right edges of the face. The face includes a step attenuated volume control with 70 incremental steps for volume adjustment and a selector knob which controls your input source selections.
DISTORTION: ±.5dB, 2Hz to 30kHx at rated output. -3dB points below 0.3Hz and above 80kHz.
GAIN: Main Output: 12.5dB Balanced, 6.5dB SE, Tape Output: 0dB
INPUT IMPEDANCE: 200K ohms Balanced, 100K ohms SE. Inputs (7): SE1, SE2, SE3, SE4, Direct (Bal), and Monitor (SE)
OUTPUT IMPEDANCE: 600 ohms Balanced, 300 ohms SE Main (2), 40K ohms minimum load and 1000pF maximum capacitance. Outputs (4): 2 Main Bal, 1 Main SE, 1 Record SE
MAXIMUM INPUT: 14V RMS maximum Balanced (7V RMS SE).
RATED OUTPUTS: 2V RMS (1V RMS SE) into 200K ohm Balanced load (maximum Balanced output capability is 30V RMS at less than 1% THD at 1kHz)
CONTROLS: Volume, Select Source, Toggle switches: Power On/Off, Mute/Operate, Monitor/Source, Direct/Source, All functions on Remote Control
POWER SUPPLIES: Electronically regulated low and high voltage supplies. Automatic 30-sec. warmup mute, Automatic brown-out mute.
NOISE: 25µV RMS residual IHF weighted Balanced noise output with gain control at minimum, (98dB below 2V RMS output)
TUBE COMPLEMENT: 4-6922/E88CC dual triode. (Vacuum tube audio circuit, solid state power supply)
POWER REQUIREMENTS: 100-135VAC 60Hz (200-270VAC 50/60Hz) 35 watts maximum.
DIMENSIONS: 19” X 5.25” X 12” (handles included)
WEIGHT: 11.6 lbs