AUDIO RESEARCH LS-25 MKII

Pre owned. In excellent condition. Free of visible signs of wear. Comes with manual and non-original remote control, without original packaging.

The Audio Research LS25 MKII represents the evolution of one of the brand’s most acclaimed preamplifiers, combining musical refinement, technical precision, and great flexibility. Derived directly from the legendary Reference One, the LS25 MKII retains the same craftsmanship and design philosophy that have always distinguished Audio Research, while introducing significant internal improvements that elevate its performance to a new level of sonic excellence.

Its design mirrors that of the original model, featuring a solid aluminum chassis, precisely machined front panels, and ergonomically arranged controls. Microprocessor-controlled knobs manage volume, balance, input selection, and gain levels, offering three sensitivity options – high, medium, and low – to optimize compatibility with sources of varying output levels. Stereo or mono mode, balanced or single-ended selection, and mute functions can also be configured, while an infrared remote control allows convenient operation from a distance. The rear panel provides a full range of balanced and single-ended connections, with seven inputs, a record output, and two pairs of main outputs.

The true advancement of the MKII lies in its completely redesigned internal architecture, featuring a new discrete-component topology. The input stage employs JFET circuitry derived from the VTM200 amplifier, followed by a cathode-follower output stage with two 6H30 twin triodes. These Russian military tubes, still in production today, are renowned for their reliability, stability, and long lifespan of up to 10,000 hours. Compared to the previous 6922-based design, the new circuitry delivers faster response, greater dynamic control, and enhanced transparency across the entire frequency spectrum.

The LS25 MKII operates in pure Class-A, with fully regulated power supplies and Infinicap coupling capacitors to ensure maximum dynamics and clarity. The result is a more lively and coherent sound, with a tightly focused soundstage, cleaner and more impactful bass, purer and airier highs, and a midrange that offers natural balance and fluid musicality. The rear-panel 12V trigger allows seamless integration into complex audio-video systems, enabling synchronized power on/off with other components.

Overall, the LS25 MKII embodies Audio Research’s philosophy: a preamplifier that combines technical rigor with genuine musicality, capable of reproducing every nuance of a recording with realism and immediacy. It not only improves upon its predecessor but surpasses it in every parameter, delivering a more open, dynamic, and coherent performance that satisfies even the most demanding listeners.

Technical specifications:

• Frequency response: ±0.5 dB from 1 Hz to 100 kHz; -3 dB below 0.2 Hz and above 400 kHz
• Total harmonic distortion (THD): <0.01% at 2 V RMS output
• Noise & hum: 14 µV RMS IHF-weighted at balanced output with gain at minimum (103 dB below 2 V RMS)
• Gain: Main output selectable for each input: 18 dB, 12 dB, 6 dB (balanced); 12 dB, 6 dB, 0 dB (single-ended); record output: 0 dB
• Input impedance: 120 kΩ balanced; 60 kΩ single-ended
• Output impedance: 650 Ω balanced; 325 Ω single-ended main (2), minimum load 20 kΩ, maximum capacitance 2000 pF
• Maximum input: 28 V balanced; 14 V single-ended (6 dB gain)
• Rated output: 2 V RMS 1 Hz–100 kHz into 200 kΩ balanced load (maximum balanced output 40 V RMS with THD <0.5% at 1 kHz)
• Power supplies: electronically regulated low and high voltage; automatic 40 s warm-up/brown-out mute; line regulation better than 0.01%
• Tubes: 2 x 6H30
• Power requirements: 100–135 V AC 60 Hz; 200–270 V AC 50/60 Hz; maximum consumption 45 W
• Other features: vacuum tube audio circuit, solid-state power supply; inputs (8): Tuner, Phono, CD, Video, Aux 1, Aux 2, Monitor, Processor (XLR and RCA); outputs (3): 2 Main, 1 Record (XLR and RCA); controls: Volume (104 steps), Gain, Balance, Input; toggle switches: On/Off, Stereo/Mono, Balanced/SE, Processor/Input, Monitor/Input, Mute/Operate
• Dimensions: 48 x 13.4 x 29.8 cm (W x H x D), handles extend 3.8 cm forward
• Net weight: 8.2 kg