Audio Research LS25 Preamp

Description

The Audio Research LS25 is a high-performance vacuum-tube line stage preamplifier introduced in 1998 by Audio Research Corporation, one of the most respected manufacturers in high-end audio. Designed as a more accessible alternative to the company’s flagship Reference series, the LS25 delivers many of the sonic characteristics and advanced features of the Reference One preamplifier in a simpler and more affordable package. With its fully balanced architecture, precision electronic controls, and classic tube-driven signal path, the LS25 quickly became a popular choice among audiophiles seeking musicality, flexibility, and exceptional build quality.

Overview

The LS25 is a vacuum-tube stereo line stage preamplifier designed to serve as the control center of a high-end two-channel audio system. It uses four 6922/E88CC dual-triode tubes in its gain stage, providing the harmonic richness and dimensionality that tube circuits are known for. Despite its tube signal path, the preamplifier employs a solid-state regulated power supply to ensure low noise, high stability, and long-term reliability.

One of the defining characteristics of the LS25 is its balanced design philosophy. The unit includes both balanced (XLR) and single-ended (RCA) inputs and outputs, allowing it to integrate easily with a wide range of high-end amplifiers and source components. Users can select between balanced and single-ended operation and adjust the overall gain in three steps, optimizing the preamp for different system sensitivities.

The LS25 also introduced several convenience features that were becoming important in modern audio systems. These include a 104-step digitally controlled volume control, remote operation, programmable gain settings for each input, and memory for user preferences. The unit automatically mutes during startup to protect speakers and equipment during tube warm-up.

Audio Research engineered the LS25 with a wide bandwidth and extremely low distortion to preserve the dynamics and tonal balance of the original recording. Its measured frequency response extends far beyond the limits of human hearing, ensuring that the audible range remains linear and free from phase anomalies.

Sound and Review Impressions

The LS25 quickly earned praise for delivering much of the sonic refinement of Audio Research’s flagship components at a lower price point.

One reviewer described its performance as “smooth and detailed, with good soundstage focus and deep bass impact.” The presentation was noted as refined yet powerful, capable of handling complex musical passages with ease.

Another evaluation emphasized the design’s lineage, noting that the LS25 felt very similar to the much more expensive Reference One preamp—“from two metres away, it looks like a Ref 1, it acts like a Ref 1 and it feels like a Ref 1.”

Owners have also praised the preamplifier for its spacious imaging and musical warmth. In one user review, the LS25 was described as offering “great soundstage, air, vibrant and musical” performance that made it a standout component in its class.

These qualities made the LS25 a versatile partner for both tube and solid-state power amplifiers, helping it remain a sought-after component on the used high-end market even decades after its introduction.

Key Features

• Vacuum-tube line stage with balanced topology

• Four 6922 / E88CC dual-triode tubes (LS25 MkI)

• Remote-controlled 104-step precision volume control

• Selectable gain settings for system matching

• Balanced and single-ended inputs and outputs

• Solid-state regulated power supply for low noise

• Automatic startup mute and protection circuits

• Memory settings for inputs and gain levels

Product Specifications

• Type: Vacuum tube stereo line stage preamplifier

• Year Introduced: 1998

• Tube Complement: 4 × 6922 / E88CC (LS25 MkI)

• Frequency Response: 1 Hz – 100 kHz (±0.5 dB)

• Distortion: <0.01% at 2V RMS output

• Signal-to-Noise Ratio: ~103 dB

• Gain: Selectable (6 / 12 / 18 dB balanced)

• Input Impedance: 120kΩ balanced / 60kΩ single-ended

• Output Impedance: 650Ω balanced / 325Ω single-ended

• Inputs: Up to 8 line-level inputs (XLR and RCA)

• Outputs: Two main outputs plus record output

• Dimensions: 19 in W × 5.25 in H × 11.75 in D

• Weight: 18 lb (8.2 kg)

Summary:
The Audio Research LS25 remains a highly respected tube preamplifier known for combining musical warmth, modern control features, and reference-grade engineering. With its balanced design, wide bandwidth, and refined sonic character, the LS25 continues to be regarded as a classic component in the lineage of Audio Research line stages.