Audio Research LS2B
At 6.0kg and just 134mm tall, it sits in a rack looking solid and serious, and it is built for balance.
Overview
The Audio Research LS2B is a line stage preamplifier from the early 1990s. It has no phono input and uses a fully balanced hybrid design. It was sold under several names: LS2B MKII, LS2B Mark II, or LS2B MkII Stereo Tube Hybrid Preamplifier. In Audio Research's history it is a transitional design that mixes solid-state reliability with the warmth of tubes. One twin-triode 6DJ8 tube sits at the core of the signal path. The rest of the circuit, power supply included, uses FET-based solid-state parts. The idea was to get the speed and control of transistors along with the harmonic richness usually associated with all-tube designs.
Owners report a clean, open sound with strong spatial imaging, particularly when paired with high-current tube amplifiers. An optional remote control added $500 to the $2,995 MSRP at launch. The preamp has five high-level inputs, though some sources list six line inputs and one tape loop system, which suggests minor revisions or configuration differences between units. Balanced XLR inputs are standard, and a fully balanced signal path was a rarity in preamps of its era at this price point. It is not a power amplifier. A single Facebook post lists 50 watts per channel, which is likely a mix-up with a power amp model, and it is disregarded.
Specifications
| Manufacturer | Audio Research |
| Product type | Preamplifier / Control Amplifier |
| External dimensions | Width 480 x Height 134 x Depth 260 mm |
| Weight | 6.0kg |
| Input terminal | Line : 6, Tape : 1 system |
| Output terminal | Unbalanced : 20V/250 Ω, Balanced : 500 Ω |
| Frequency characteristic | 1 Hz to 100 kHz ± 0.5 dB |
| Power consumption | 60W |
| Controls | Gain, Power |
| Balanced input impedance | 3M ohms |
Key Features
Fully Balanced Hybrid Tube and Solid State Design
The LS2B uses a balanced hybrid topology, a deliberate choice to combine solid-state and tube technologies. Most of the signal path, including regulation in the power supply, uses FETs as the main active components, which keeps noise low and current stable. The single 6DJ8 twin triode is used selectively within the gain stage and adds subtle harmonic saturation without compromising control. This layout avoids the microphonics and drift common in all-tube preamps while keeping tonal richness.
Line-Only Control Amplifier with Balanced XLR Inputs
The LS2B is strictly a line-level preamplifier. It has no phono circuitry at all, so the design concentrates on handling high-level signals. Its six line inputs include balanced XLR connectors, so users can take full advantage of the internal balanced circuitry with compatible sources. The high 3M ohm input impedance puts minimal load on upstream devices, preserving transient detail and dynamics.
Low-Noise Tube Implementation with FET Support
The 6DJ8 tube is specified as a "QUALITY LOW-NOISE TUBE," selected for reliability and quiet operation. It sits in the gain stage, in a carefully regulated environment supported by solid-state FET circuitry. This hybrid topology reduces the need for excessive global feedback, which contributes to a more natural, dynamic presentation. Some users have reported audible hiss, particularly in high-gain systems, which indicates that tube matching and circuit aging may affect noise performance over time.
Collectibility & Value
The LS2B was produced in 1992, so units are well over 30 years old today. In 2013, Audio Research Lab listed a quotation range of 1,000 to 1,200 EUR for units in working condition. One example arrived for service in good working order and received only a light service, which suggests inherent reliability when maintained. A unit refurbished by Audio Research in early 2024 indicates that factory support, at least for servicing, may still exist or have been available recently. User feedback on forums gives it a 4.9 out of 5 rating, reflecting strong satisfaction among owners. The primary user complaint is excessive gain when paired with sensitive power amplifiers. No data is available on spare parts availability or common failure modes beyond occasional hiss.
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