The LS25 vacuum tube stereo line preamplifier offers sonic performance, functional flexibility and value second only to the world-renowned Reference One preamplifier. It is unprecedented measured by any performance criteria at its price.
Many will perceive the LS25 as a more compact REF1 — and to be sure, there are many similarities in the mechanical design. Chassis construction is like the REF1, with finished slab sides and heavy top and bottom covers; chassis height and depth are slightly reduced, however. Front-panel control layout is also familiar: microprocessor-controlled rotary devices are used for overall gain set (High, Medium and Low), volume, balance and input selection. Two-way toggle switches control Power On / Off, Stereo / Mono, BAL / SE, Processor / Input, Monitor / Input and Mute. The selectable overall gain function allows a wider range of volume-control operation for input sources having different output levels (for example: a phono stage vs. a high-output D/A converter). The A-V processor to control overall system volume level instead of the LS25’s volume control when used in this mode. Thus, the LS25 fits smoothly into any high-performance installation which combines audio and video playback functions.
The rear panel offers a full complement of audiophile-grade balanced and single-ended connectors: seven inputs (including tape monitor), a tape / record out and two sets of main outputs. Balanced or single-ended optimization for every input is selected via the front-panel toggle, and is automatically remembered (along with previously selected gain level) by the LS25’s internal memory. All functions (except gain and SE / BAL) are addressable via the supplied handheld IR remote control. A.C. power is supplied at the rear panel via a three-pin IEC socket and 14-gauge detachable power cord.
Inside, the LS25 is pure Class-A operation Audio Research: gain is supplied via four 6922 twin triodes, with fully regulated massive power supplies and Infinicap coupling caps at the output for maximum dynamics and transparency. Performance is smooth and detailed, with good soundstage focus and plenty of deep bass impact. The overall presentation is refined, yet with power that extends effortlessly into the frequency extremes. Like the REF1, the LS25 never meets a sonic challenge it can’t handle with aplomb — and it does so while offering all the features needed to fit into today’s multipurpose entertainment systems.
[From the ARC website]