Onkyo TX-4500MKII (1979–1980)
A quartz-locked stereo receiver that brought broadcast precision and modular flexibility to the heart of the 1970s hi-fi stack
Overview
The Onkyo TX-4500MKII weighs 15.5 kg. It's a full-function stereo receiver that also works as a standalone preamplifier and high-performance FM section. Onkyo marketed it as a "Quartz-Locked Stereo Receiver," and it came out while the company was refining its analog engineering to meet audiophile demands for tuning accuracy and signal purity. People often mistake it for a simple tuner. It's better understood as a hybrid: a receiver built like a modular component system, where you can bypass the internal amplifier and use the preamp and tuner sections independently. That appealed to buyers who already owned a high-current power amp or wanted to build a system piece by piece. It measures 583 mm wide, 163 mm tall, and 430 mm deep, so it fills a standard rack bay, and the heavy steel chassis underneath resists vibration and contributes to long-term stability.
Key Features
Quartz-Locked FM Tuner with Double-Conversion Design
The TX-4500MKII's most celebrated feature is its quartz-locked FM tuning system, a technology Onkyo pioneered and refined across generations. Standard variable-capacitor tuners could drift with temperature or age. This one used a quartz crystal reference to lock onto stations with exceptional stability. The double-conversion superheterodyne design minimized image frequency interference and improved selectivity, especially in urban areas where adjacent stations bled into one another. A high-gain RF amplifier boosted weak signals, and a precision-lapped tuning capacitor kept dial tracking smooth and accurate. The illuminated analog dial is backlit in soft blue, so it stays readable in dim rooms. Grouped controls sit under a crystal-clear solid plate glass cover, which protects the switches while keeping them accessible. Contemporary reviews noted the clarity and usability of that design. High Fidelity (June 1978, p.101) described the layout as having "functions [that] are more prominent and in full view at all times, protected by crystal-clear solid plate glass."
Discrete Transistor Preamplifier Section
The preamplifier stage uses discrete transistor circuitry, with no ICs in the signal path, and is engineered for low noise and high transparency. It can run as a standalone preamp with an external power amplifier, which was a rarity in receivers of this class. The tone controls offer ±10 dB adjustment at 100 Hz and 10 kHz. A "Twin Turbo" option gives ±15 dB at 50 Hz and ±6 dB at 10 kHz for more aggressive shaping. A full tape loop with monitor switching lets you record from any source while listening to another, a crucial feature in the era of cassette dubbing and reel-to-reel archiving.
High-Power Output Stage
Exact impedance-specific power ratings are not confirmed in available documentation. Sources suggest the amplifier section delivers approximately 60 watts per channel, and one listing cites a total RMS power rating of 120W, potentially indicating 60W per channel into 8 ohms. It remains unclear whether that figure was achieved under full bandwidth or dynamic conditions. Owners report occasional struggles to reach rated output, possibly due to aging power supplies or component drift. Gold-plated RCA jacks and high-quality potentiometers ensured clean signal transfer, and the internal layout supported stable operation under continuous load.
Historical Context
The TX-4500MKII was introduced in 1979 and produced through 1980. Integrated receivers dominated the mid-to-high-end market then, combining tuner, preamp, and power amp in one chassis. Onkyo positioned the model as a mid-range offering, balancing advanced tuning technology with modular versatility. It followed the original TX-4500 and was Onkyo's second-generation quartz-locked design, improving on the first with refined ergonomics and enhanced circuitry. Audio (January 1979, p.89) referred to it as "the finest" in its class, noting that "Onkyo's innovative genius was improving on the first to produce the finest." It never achieved the same name recognition as contemporaries like the Yamaha TU-3000 or Sony ST-555ES, and remains a cult favorite rather than a mainstream name.
Collectibility & Value
Well-maintained units in working condition typically sell for $250 - $400, with fully restored examples going higher, up to $599 for units described as having "very nice sound." Units listed as "AS-IS" or for parts have sold for around $430, which suggests demand even for non-functional units, likely due to their serviceable chassis and sought-after faceplates. Owners note a growing cult following among vintage tuner enthusiasts, and one Facebook poster called it "a nice pice of history." Common issues include dried-up electrolytic capacitors in the power supply and audio coupling paths, which can cause hum or distortion if not replaced. The volume and tone controls often develop crackling from dust or wear, though contact cleaner may help. The large tuning capacitor may stiffen over time and benefit from specialized lubricant, never general-purpose oil. A recurring hardware failure involves resistor R616 on the power amp board, which has been reported as burned in multiple user posts, often linked to transistor Q607. Some owners have also reported difficulty sourcing spare faceplates, which points to parts scarcity for cosmetic restoration.
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