Kenwood KT-5500 (1975)
At 5.7kg, it sits on the shelf and looks like a tuner meant to be taken seriously.
Overview
The Kenwood KT-5500 is an FM stereo tuner released in 1975 by TRIO-KENWOOD. It was designed with a clear emphasis on FM sound quality, at a time when high-fidelity tuners were becoming essential parts of audiophile systems. The original price was ¥38,000, a premium segment of the Japanese market, aimed at listeners who valued precision and low distortion in broadcast reception. No broader market context or competitive positioning is documented. What the page does have is a detailed internal architecture and a set of measured performance specs.
The primary documentation has no professional reviews or user testimonials. Owner reports from later years are mixed. Some units power on and look fine, but fail to tune, which points to possible problems in the RF or oscillator stages. Others have a persistent fault: the stereo indicator LED fails to illuminate even on strong local stations, and this recurs across user accounts. These reports are anecdotal, but they suggest long-term reliability may vary. A service manual exists for both the KT-5500 and its sibling model KT-5550, and it is available through enthusiast archives and eBay. DIY modification guides also exist, so there is a small but active community restoring these units.
Specifications
| Manufacturer | TRIO-KENWOOD |
| Product type | FM stereo tuner |
| Production years | Released in 1975 |
| Original price | ¥ 38,000 |
| Receiving frequency | 76 MHz to 90 MHz |
| Antenna impedance | 300 Ω equilibrium 75 Ω unbalance |
| Sensitivity (IHF) | 1.7 μV |
| SN ratio | 50 dB quieting sensitivity |
| Quieting sensitivity | Mono : 3.7 μV Stereo : 43 μV |
| Distortion Factor (400 Hz, 100% modulation) | mono:0.1% stereo:0.15% |
| Signal-to-noise ratio (100% modulation, 1 mv input) | mono:75dB stereo:70dB |
| Image ratio | 110dB |
| Selectivity (IHF) | 85dB |
| IF interference ratio | 100dB |
| Harmonics spurious response | 120dB |
| AM suppression ratio | 60dB |
| Capture ratio | 1.0dB |
| Stereo separation | 45dB(400Hz) 37 dB (50 Hz to 10 kHz) |
| Carrier leakage | 65dB |
| Frequency characteristic | 30 Hz to 15 kHz + 0.2 -1.5 dB |
| Output Level / Impedance FM (400 Hz, 100% modulation) | Variable : 0 ~ 1.5V/2.5k Ω Fixed : 0.7V/4.5k Ω |
| FM det out | 250mV |
| Multipath output | 0.2 V |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Rated power consumption (Electrical Appliance and Material Control Law) | 13W |
| External dimensions | Width 380x Height 140x Depth 255 mm |
| Weight | 5.7kg |
Key Features
Frequency Linear 5-Row Variable Capacitor with Built-In Oscillation Circuit
The front end of the KT-5500 uses a frequency linear 5-row variable capacitor, chosen for precise tuning alignment. This varicon is built to keep scale accuracy high by tying the rotation angle closely to frequency, which minimizes tuning errors across the dial. The oscillation circuit is integrated directly into the capacitor assembly. Kenwood did this to reduce phase shifts and improve tracking stability, which matters for stereo separation and drift.
Three-Dimensional Wiring and Block Construction
To fight frequency drift from temperature and humidity changes, the KT-5500 uses a three-dimensional wiring layout with modular block construction in the station selection section. This isolates the sensitive RF and oscillator stages, reducing thermal coupling and mechanical stress on components. The tuning platform stays more stable over time, which helps for listeners who left their tuners powered for long periods.
Three Dual-Gate MOS-Type FETs in RF and Mixer Stages
Three dual-gate MOS-type FETs are used in the two RF stages and the mixer stage, to improve intermodulation performance. These transistors have high input impedance and low noise, which helps preserve weak signals while rejecting strong adjacent-channel interference. All of this happens before the signal reaches the IF stage.
Phase-Linear 8-Element IF Filter with 6-Stage Limiter
The intermediate frequency (IF) section has an 8-element phase-linear filter, designed for high selectivity with excellent group delay characteristics. That keeps phase distortion across the audio band to a minimum and preserves stereo imaging. It is combined with a high-gain amplifier and a 6-stage limiter. The IF chain is built to suppress interference and keep signal overload from degrading the sound, even with strong signals.
Wide-Band Quadrature Detector with Offset Voltage Adjustment
Kenwood used a wide-band quadrature detector circuit, which allows accurate FM demodulation across a broad frequency range. It includes adjustable offset voltage, so the circuit reaches low distortion over the entire bandwidth. That reduces the harmonic and intermodulation artifacts that could otherwise color the audio output.
PLL-Based MPX Section with Current Adjustment Circuit
The MPX (multiplex) decoder uses a novel phase-locked loop (PLL) design. It adds a current adjustment circuit to the multiplier-based stereo demodulator. This reduces demodulation distortion, a common weak point in FM tuners of the era. The aim is cleaner separation between left and right channels and a more accurate reconstruction of the original stereo signal.
±2 Power Supply Differential Direct-Coupled Audio Amplifier
The audio output stage is a differential direct-coupled amplifier powered by a ±2V supply. It has a wide dynamic range and can handle up to 300% overmodulation without clipping, far beyond standard broadcast levels. Combined with a low distortion factor, the output stays clean even under extreme modulation.
Relay Muting Circuit Driven by Schmidt Trigger
The muting system is a relay-based circuit activated by a Schmidt trigger. The trigger is driven by a synthesized signal that combines antenna input strength and the discriminator S-curve. Audio is only unmuted when a stable, listenable signal is present. This prevents loud pops and noise bursts during tuning or when the signal is lost.
Metal Glazed Semi-Fixed Volumes for Critical Adjustments
For long-term reliability, metal glazed semi-fixed potentiometers are used at the critical calibration points: offset voltage, separation, and PLL-VCO adjustment. They resist degradation from temperature swings and humidity, which helps hold factory alignment over the years.
75 Ω F-Type Connector in Addition to Standard Antenna Terminals
Besides the standard 300 Ω balanced and 75 Ω unbalanced inputs, the KT-5500 has a 75 Ω F-type connector, an uncommon feature for 1975. This coaxial port makes it easier to connect newer antennas or distribution systems.
Rich Output Terminal Configuration
The tuner has several output options: variable and fixed-level preamp outputs, an FM detector output, and a multipath output. That lets it work with a wide range of preamplifiers, recording devices, or external stereo decoders, in both contemporary and modern system setups.
Collectibility & Value
No current market prices or formal collectibility assessments are documented. Owners report recurring issues such as failure to tune and the stereo indicator LED not illuminating, which suggests possible reliability concerns. A service manual is available through enthusiast sites and eBay, and DIY modification resources exist, so repair looks feasible for technically inclined users. The separate wood case SRA-3000, originally priced at ¥4,500, was sold as an optional accessory.
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