audio research

Tube stereo line stage.



LS5 MKII (1994)

From the ARC website

Be assured: The LS5 MarkII stereo line-level preamplifier from Audio Research is no mere nostalgic nod to the past. Rather, it represents a significant advance in the technology of vacuum-tube amplification as applied to the retrieval and transmission of meaningful musical information from any input source, analog or digital. The difference is one you will hear immediately in your music system-and never forget. The technology making this all possible includes a sophisticated, fully regulated power supply using patented Decoupled Electrolytic Capacitor circuits; fully balanced, cross-coupled, all-vacuum-tube amplification stages; and switch-selectable gain allowing a wider range of useful volume control settings with different input sources. All this, plus the harmonic richness and timbral magic of dual-triode vacuum tubes. From the manufacturer with 25 years of experience in bringing recorded music to life. If ever there has been a preamplifier that will markedly-even astoundingly- improve the performance of any deserving audio system, the LS5 MarkII is it. You'll hear your favorite music as though illuminated from within, played specially for you. Intimate. Profound. Lasting. The way music was meant to be experienced, and remembered.

The LS5MKII confirms once again the sonic leadership of Audio Research in the arena of preamplifier design. Combining the most advanced, fully differential circuit topology with dual-triode vacuum tube gain and solid-state regulation, the LS5MKII is a remarkable performer. One look at the chassis back panel of the LS5MKII tells you this is no ordinary line preamp. An imposing array of six sets of professional-grade XLR input connectors, plus three sets of XLR output connectors, clearly proclaims the fully-balanced circuit design of the LS5MKII. This uncompromising approach means the LS5MKII can utilize the benefits of fully differential operation (along with Audio Research's proprietary cross-coupling) to minimize noise and reduce susceptibility to externally-induced RF noise as well.

The result is a startling ability to portray even the finest acoustic details and dynamic contrasts against a velvety background. Meanwhile, the rugged, linear operation of the ten dual-triode 6922 tubes provide 30 dB of overall gain. When used in conjunction with the Audio Research PH2 phono preamplifier, a total of 78 dB of gain is available, sufficient for the great majority of today's finest moving-coil cartridges. Meanwhile, a front-panel toggle allows the gain to be reduced to 12 dB for use with high-output digital processors, high-sensitivity amplifiers or ultra-efficient loudspeakers. (The Audio Research DAC2 digital converter may be used with either gain setting.) The selectable high-low gain of the LS5MKII gives the user optimal flexibility for best sonics with any input source.

The power supply of the LS5MKII employs the latest FET technology for maximum stability and tight regulation of amplification stages under all operating conditions. A low-noise toroidal transformer, coaxial capacitors and Audio,Research's patented decoupling capacitor circuits (DECs) all contribute to tremendous dynamic control and powerhouse bass extension and impact. The LS5MKII is truly at home under all musical conditions. And, to enable proper connection of input sources having only single-ended outputs, ask your dealer about the Audio Research BL2-a selectable-input balanced line driver which allows you derive a balanced signal from up to five single-ended sources, plus built-in tape handling capability. Thanks to the BL2's high input impedance and low output impedance, your favorite sources will sound their absolute best when feeding a signal to the LS5MKII. While the professional industry and re- cording studios have used balanced operation and connections as a standard for many years, the consumer electronics industry is only now gradually adapting its products to this superior format. With the LS5MKII, you will be ready to take advantage of the latest balanced-output sources as they become available, yet you can enjoy its remarkable sonic abilities today.

LS5 MKIII (1996)

Remote control $500 (1994)

MSRP (US new retail)
$4,995 (LS5 MKII)
$5,495 (LS5 MKIII)


Frequency response ±.5dB, 1Hz to 100kHz.
LS5 MKIII: ±.5dB, 1Hz to 200kHz -3dB points below 0.3Hz and above 400kHz.
Distortion (THD) Less than .01% at 2V RMS output (typically <0.005% in midband)
LS5 MKIII: Less than .005% at 2V RMS output
Noise & hum 40µV RMS residual IHF weighted balanced noise output with gain control minimum, 12dB gain selected (94dB below 2V RMS output)
LS5 MKIII: 13µV RMS residual IHF weighted balanced noise output with gain control minimum (12dB gain), (103dB below 2V RMS output)
Gain (Balanced Differential): Main output 30dB/12dB switchable.
Tape output: 0dB.
Input impedance 200K ohms balanced
Output impedance 400 ohms balanced Main (2), 20K ohms minimum load and 2000pF maximum capacitance.
Output polarity  
Maximum inputs LS5 MKIII: 20V
Rated outputs LS5 MKIII: 2V RMS 1Hz to 100kHz into 100K ohm balanced load (maximum balanced output capability is 30V RMS at less than 0.5% THD at apability is 30V RMS at less than 0.5% THD at 1kHz).
Power supplies LS5 MKIII: Electronically regulated low and high voltage supplies. Auto 45 sec. warm-up/brown-out mute. Toroid power transformer. Line regulation better than .01%.
Tube complement LS5: (4) 6922, (6)12BH7
  LS5 MKII: (10) 6922
  LS5 MKIII: (8) 6922/E88cc dual triode. (Vacuum tube audio circuit, solid-state power supply.)
Power requirements 100-135VAC 60Hz (200-270VAC 50/60Hz) 100 watts maximum.
Dimensions 19" (48 cm) W x 5¼" (13.4 cm) H (standard rack panel) x 11¾" (29.8 cm) D. Handles extend 1½" (3.8 cm) forward of the front panel. Rear chassis fittings extend 7/8" (2.3 cm).

19 lbs. Net 29 lbs. Shipping
LS5 MKIII: 17.5 lbs. (8.0 kg) Net; 30 lbs. (13.6 kg) Shipping.



Vol. 17 No. 8 (LS5), Vol. 17 No. 11 (LS5), Vol. 17 No. 12 (LS5 MKII), Vol. 18 No. 7 (LS5 MKII), Vol. 19 No. 2 (LS5 MKII)