Kenwood KA-5500 (1975)

At 10.5kg, it sits on the rack like a precision instrument—dense, deliberate, and wired for fidelity.

Overview

The Kenwood KA-5500 is a stereo integrated amplifier released in 1975 by TRIO-KENWOOD, a period when Japanese engineering was redefining high-fidelity expectations. Known in some markets as the Trio KA-5500, this unit 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 to impress with flash or flair, but rather to disappear into the system—doing its job with minimal fuss and maximum control.

While the fact sheet doesn’t place it within a broader product lineage, user observations suggest it shares the styling language of larger models in the KA series, The amplifier combines phono, tuner, and auxiliary inputs with a robust power section, making it a self-contained hub for a complete analog setup. Though no contemporary reviews or marketing context survive in the documentation, its continued presence in enthusiast circles more than four decades later speaks to a quiet reputation earned through performance, not promotion.

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), a design choice aimed at minimizing phase shift and improving transient response. This topology was relatively advanced for its time, helping the KA-5500 extract detail from vinyl without the smeared attack that plagued many budget and mid-tier competitors. The RIAA curve accuracy is tight—within ±0.3 dB—ensuring tonal neutrality across the frequency band.

All-Stage Direct-Coupled OCL Power Amplifier

The power amplifier section is built around a pure complementary symmetry OCL (Output Capacitor-Less) circuit, fully direct-coupled from input to output. This eliminates coupling capacitors in 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, enhancing thermal stability and reducing drift. The result is a solid 55W RMS per channel into 8 ohms across the full 20Hz–20kHz range, with distortion held to a firm 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, providing a stable reservoir for dynamic transients. This supply design supports a damping factor of 30, giving the amplifier firm control over speaker cones, especially in the bass region. Notably, collectors have observed that all internal circuit boards are manufactured by Elna, a respected Japanese component supplier, suggesting a commitment 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. These meters are not decorative—they’re calibrated to read output directly from 0.01W to 60W, with a switchable range between 60W and 3W for fine resolution at low levels. While a point of pride in the original design, these meters have become a known failure point; owners frequently report inaccurate readings due to solder joint issues on the meter range switch, requiring rework or replacement.

Selectable NFB Tone Control with Defeat Mode

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

Subsonic Filter and -20dB Attenuator

Equipped with a 18 Hz, 12dB/octave subsonic filter, the KA-5500 can effectively block infrasonic rumble from warped records or turntable vibration. A separate -20dB attenuator allows for quick level reduction, useful when switching between sensitive sources or avoiding speaker damage during setup. These features reflect a thoughtful approach to real-world usability, not just spec-sheet performance.

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, suggesting strong demand for complete, well-preserved systems. However, individual units have appeared at lower valuations—tapeheads.net noted one priced at $100 in a charity resale store as early as 2017, indicating wide variability based on condition and market.

Common issues include failure of the meter range switch solder joints, leading to erratic or dead meters, and problems with the treble/bass bypass switch, which can cause intermittent operation or channel dropouts. Static from the volume control is occasionally reported, often pointing to wear in the 41-click potentiometer, which may require 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, reflecting an active support ecosystem among enthusiasts.

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