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At US$950, this is the more appealing alternative to chasing a pricier, fully serviced example: it sits just above the US$898 25th percentile but below the US$1,000 median, making it a fair-to-good buy rather than an ambitious ask. For a substantial vintage power amplifier, the price is attractive if it is demonstrably functional.
The M-504 remains well regarded for its muscular dual-mono design, 165 watts per channel into 8 ohms, strong dynamics, and smooth, slightly warm presentation. Its large meters and serious build give it genuine enthusiast appeal, while the power suits demanding speakers better than many modern budget amplifiers. Since this is an older unit, confirm both channels are quiet and stable, meters and protection circuitry work, and there is no evidence of overheating or intermittent operation; a recent service would strengthen the case considerably.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
Onkyo traces its roots to postwar Japan, founded in 1946 in Osaka by Takeshi Goda, an engineer at Matsushita Electric who envisioned high-quality Japanese loudspeakers. Initially established as Osaka Denki Onkyo K.K., the company began production in 1948 with the acclaimed ED-100 speaker featuring a 25 cm driver, quickly building a reputation through LP concerts and innovative designs that resonated with audiophiles.
The brand excels in premium home audio, renowned for AV receivers, hi-fi amplifiers, and surround sound speakers that deliver exceptional clarity and power. Its portfolio spans turntables, DACs, headphones, and cables, bolstered by acquisitions like Pioneer's home electronics division in 2015, enabling cutting-edge integrations such as internet radio and high-resolution streaming.
Onkyo holds a solid mid-tier position in the hi-fi market, prized by discerning buyers for reliable performance and value rather than ultra-high-end exotica. Despite bankruptcy challenges in the late 2010s, its revival under new ownership preserves a legacy of technological innovation and pure sound enjoyment, appealing to both vintage enthusiasts and modern home cinema setups.
See all Onkyo listings on RADAR.
