The Audio Research LS5 MKII is a high-end balanced tube line-stage preamplifier that continues to be celebrated by audiophiles for its rich tube warmth, transparency, and ability to deliver a spacious, detailed soundstage. Building on the success of the original LS5, the MKII version introduces refinements that elevate its performance even further. As part of Audio Research’s long-standing tradition of excellence, the LS5 MKII is one of the most revered line stages for those looking for the purest possible sound from a tube preamp.
Production
1993
Condition
9.5/10
Serial No.
73366020
Orig. MSRP
$4,995
Restoration
Verified all inputs and outputs
Cleaned all pots and switches
Replaced bad 22uf 100v capacitor in power supply
Verified remote control operation
All tubes test good
Factory Specs
Frequency response
LS5: ±.5dB, 1Hz to 100kHz. -3dB points below 0.1Hz and above 250kHz. LS5 MKII: ±.5dB, 1Hz to 200kHz. -3dB points below 0.1Hz and above 600kHz. LS5 MKIII: ±.5dB, 1Hz to 200kHz. -3dB points below 0.3Hz and above 400kHz.
Distortion (THD)
LS5: Less than .01% at 2V RMS output (typically less than 0.005% in midband). LS5 MKII: Less than .005% at 2V RMS output (typically less than 0.003% in midband). LS5 MKIII: Less than .01% at 2V RMS output
Noise & hum
LS5: 40µV RMS residual IHF weighted balanced noise output with gain control minimum, 12dB gain selected (94dB below 2V RMS output). LS5 MKII: 12µV RMS residual IHF weighted balanced noise output with gain control minimum, 12dB gain selected, (104dB 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
LS5/LS5 MKII: (Balanced Differential): Main output 30dB/12dB switchable. Tape output: 0dB. LS5 MKIII: (Balanced Differential): Main output 12dB (Optional 18dB). Tape output: 0dB.
Input impedance
200K ohms balanced
Output impedance
400 ohms balanced Main (2), 20K ohms minimum load and 2000pF maximum capacitance.
Maximum inputs
20V maximum
Rated outputs
LS5/LS5 MKII: 2V RMS 1Hz to 100kHz into 100K ohm balanced load (maximum balanced output capability is 50V RMS at less than 0.5% THD at 1kHz). 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 1kHz).
Power supplies
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/E88CC, (6)12BH7A. LS5 MKII: (10) 6922/E88CC. LS5 MKIII: (8) 6922/E88CC
Power requirements
LS5: 100-135VAC 60Hz (200-270VAC 50/60Hz) 130 watts maximum. LS5 MKII/LS5 MKIII: 100-135VAC 60Hz (200-270VAC 50/60Hz) 100 watts maximum.
Other
Vacuum tube audio circuit, solid-state power supply. Inputs (6): tuner, video, phono, CD, aux, tape (XLR connectors). Outputs (3): 2 main, 1 tape (XLR connectors) Controls: Gain, Quad detented, input selector. Toggle switches: power/off, +30/+12dB gain, monitor/source, mute/operate.
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 ⅞" (2.3 cm).
Weight
LS5/LS5 MKII: 19 lbs. (8.6 kg) Net, 29 lbs. (13.2 kg) Shipping. LS5 MKIII: 17.5 lbs. (8.0 kg) Net; 30 lbs. (13.6 kg) Shipping.
The History of Audio Research
Audio Research Corporation, affectionately known to fans as ARC, was founded by William Z. Johnson, who began designing custom audio electronics in the early 1950’s and who also operated a specialty audio retail store until the mid-1960’s. Johnson’s efforts almost single-handedly revived vacuum-tube designs at a time...
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Liner Notes
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.
Stock No.
8829862707421
