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Excellent condition Onkyo M-504 Stereo power amplifier. This unit was just fully serviced, cleaned and calibrated and is in perfect working condition. All of the lights are functioning as they should, gorgeous rosewood panels and HUGE VU Meters ! This is a beautiful piece that offers an incredible sounds stage ! Please see pictures as those are also part of the description Price includes FREE shipping to the lower 48 states, will be packed, tracked, fully insured, and delivered to your address for free. Local pick up on Long Island New York also more than welcome. Thank you. 
This is a seller’s market at this price: at US$1,500, the ask sits above the US$1,400 75th percentile and looks ambitious versus the US$1,050 median for recent comparable US listings. It is not an automatic no, but the premium needs real justification from condition, service history, and completeness.
The M-504 is well-regarded for big, authoritative power and a clean, muscular vintage Onkyo sound, so a tidy example still has appeal to collectors and listeners who want classic Japanese build quality. At this level, a buyer should want proof of healthy operation, unmolested cosmetics, and any original accessories or documentation; if those are absent, the price is hard to defend.
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.
