Kenwood KA-5500 (1975)

At 10.5kg, it sits on the rack like a precision instrument - dense and deliberate.

Overview

The Kenwood KA-5500 is a stereo integrated amplifier released in 1975 by TRIO-KENWOOD. Some markets knew it as the Trio KA-5500. It was built to deliver clean, uncolored power with an emphasis on stability and low distortion. Owners report a soundstage that's consistently described as crisp and stable, with a clarity that doesn't fatigue over long listening sessions. It wasn't designed for flash. It was meant to disappear into the system and do its job with minimal fuss and maximum control.

The fact sheet doesn't place it within a broader product lineage, but user observations suggest it shares the styling of larger models in the KA series. The amplifier combines phono, tuner, and auxiliary inputs with a power section, so it works as a self-contained hub for a complete analog setup. No contemporary reviews or marketing context survive in the documentation. It is still around in enthusiast circles more than four decades later.

Specifications

Key Features

FET Differential Amplification ICL in Phono Stage

The phono equalizer stage uses a first-stage FET differential amplification with Infinite Cascode Loading (ICL). The aim was to minimize phase shift and improve transient response. This topology was relatively advanced for its time, and it helped the KA-5500 pull detail from vinyl without the smeared attack that plagued many budget and mid-tier competitors. RIAA curve accuracy is within ±0.3 dB.

All-Stage Direct-Coupled OCL Power Amplifier

The power amplifier section is a pure complementary symmetry OCL (Output Capacitor-Less) circuit, fully direct-coupled from input to output. That removes the coupling capacitors from the signal path, which can degrade low-frequency phase coherence and transient response. The first stage uses differential amplification, and the class A load circuit is stabilized with a constant current source, which helps thermal stability and reduces drift. Output is 55W RMS per channel into 8 ohms across 20Hz - 20kHz, with distortion held to 0.1% at rated output.

High-Regulation Power Supply with Elna Boards

A large, well-regulated power transformer feeds two 10,000 μF electrolytic capacitors, a stable reservoir for dynamic transients. The supply supports a damping factor of 30, which gives the amplifier firm control over speaker cones, especially in the bass region. Collectors have observed that all internal circuit boards are made by Elna, a respected Japanese component supplier, which suggests attention to quality control in materials and assembly.

Independent Direct-Reading Power Meters

Flanking the central controls are left and right power meters, with a 41-click detent volume knob between them. The meters are calibrated to read output directly from 0.01W to 60W, with a switchable range between 60W and 3W for fine resolution at low levels. They were a point of pride in the original design, and they are now a known failure point. Owners frequently report inaccurate readings from solder joint issues on the meter range switch, which need rework or replacement.

Selectable NFB Tone Control with Defeat Mode

The tone controls use a low-distortion, selectable negative feedback (NFB) design, with the bass and treble networks placed inside the feedback loop. This reduces the effect of the controls on overall circuit linearity. In defeat mode, the CR networks are fully disengaged, and the stage reverts to a buffer amplifier with excellent DC stability and phase characteristics. The straight-through path is genuinely transparent.

Subsonic Filter and -20dB Attenuator

The KA-5500 has an 18 Hz, 12dB/octave subsonic filter, which can block infrasonic rumble from warped records or turntable vibration. A separate -20dB attenuator allows quick level reduction, useful when switching between sensitive sources or avoiding speaker damage during setup.

Collectibility & Value

The Kenwood KA-5500 is valued by vintage collectors, particularly those focused on Japanese solid-state amplifiers from the 1970s. A set including the KA-5500 amplifier and matching KT-5500 tuner sold for $650 in "Used - Very Good" condition, which suggests strong demand for complete, well-preserved systems. Individual units have appeared for less. tapeheads.net noted one priced at $100 in a charity resale store as early as 2017, so prices vary widely with condition and market.

Common issues include failure of the meter range switch solder joints, which leads to erratic or dead meters. The treble/bass bypass switch also gives trouble, with intermittent operation or channel dropouts. Static from the volume control is occasionally reported, often pointing to wear in the 41-click potentiometer, which may need cleaning or replacement. Bias and DC offset drift are also mentioned in repair discussions, typical of aging transistors in direct-coupled designs. Restoration kits, including genuine parts, are available for comprehensive servicing.

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