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The unit was purchased second hand and externally is in good shape. While I don’t know much about stereo equipment I did attempt to test it and I was unable to get it to play. I hear a relay click when powered on and the green lights while dim to come on but I not able to get it to play. I don’t know how to diagnose the issue so it will be sold as is without returns so please reach out if you have any questions or need more pictures
This US$700 ask is a strong deal for the Onkyo M-504, landing well below the 25th percentile of US$961 and significantly under the median of US$1,050 from our recent comparable listings. While scattered external chatter suggests values closer to US$300–US$400 or even a French listing near US$850, the database anchor of US$1,050 median confirms this listing offers genuine bargain value for a working unit.
The M-504 is a revered vintage Integra power amp known for its clean, robust sound and durability, making it a prized main amp for enthusiasts seeking vintage reliability without modern fluff. At this price, the upside is immediate: you secure a well-loved, high-current amplifier that often pairs beautifully with classic Onkyo preamps like the P-304, turning a single buy into a full-system upgrade opportunity if accessories are included.
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.
