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This is an extremely impressive amplifier designed by Nelson Pass using 32 MOSFET (HEXFET) output devices. The amp uses 3 stages of gain vs. the 5 often used by its peers. The amplifier is very smooth, producing good inner detail. It is capable of driving almost any load and delivers stunning dynamic range. They are biased AB1 towards class A operation. Big dynamics and really nice sound. Warm and smooth delivery. The power is awesome at 300 RMS watts per channel! Quite affordable as all Adcom products are.I am the original and only owner. I used it for 5 years and since then its been stored in a un-used bedroom closet as I moved to another location where this large stereo setup could not be used. I currently have an integrated and much smaller speakers, as the wife got her way.It was used to drive a pair of Magnepan 1.6QR (Maggies) which present a 4 ohm load to the amp. This amp shows minimal ware, if any. The gold plate still looks new, see pics. It's been inside a shipping box for years now, I only unsealed/unpacked it in order to test play it to confirm it still sounds great ( again see pics). I have attached photos taken during this testing and recorded a small segment of video of of the operation with LEDs on, volume adjustment and playing a song through the Maggie's. It was done in a tight space as you can see but I believe it gets the point across. See/listen to video to confirm operation.Looks factory fresh except for a little dust in crevices. The plating on i/o connectors look great, no discoloration or oxidation. It was never rack mounted. Metal shows no pitting and no discoloration.Comes with a 120V cord as pictured and the original Owners manual Core Power SpecificationsPower Output (8Ω): 300 Watts per channel (continuous average power, 20Hz–20kHz).Power Output (4Ω): 450 Watts per channel.Dynamic Headroom: 2.3 dB.Damping Factor: 700Audio PerformanceFrequency Response: 3Hz to 130kHz (+0, -3dB).Total Harmonic Distortion (THD): <0.18% at 8Ω (full power); some sources note as low as 0.015% under specific loads.Signal-to-Noise Ratio (SNR): >105dB (A-weighted).Input Impedance: 105kΩ.Input Sensitivity: 1.7V RMS for 300W into 8ΩPhysical & Technical FeaturesInputs: Includes both Balanced (XLR) and Unbalanced (RCA) inputs.Speaker Terminals: Two pairs of gold-plated 5-way binding posts per channel to support bi-wiring.Cooling: I never had any issues running the Magnepan's 1.6QR's with heat nor did I provide artificial cooling but it did have adequate ventilation around it.Dimensions: 17" W x 8" H x 14" D.Weight: Approximately 48 lbs (21.8 kg) before packing materials.I support a local pickup or meet close by. I am willing to ship insured at Buyers expense within USA.
Condition is unknown, but at US$1,199 this sits below the US$1,224 25th percentile of recent asking prices and looks like a strong buy rather than a stretch. Against a median of US$1,350 and a 75th percentile of US$1,474, the price leaves room for a little uncertainty without drifting into bargain-bin territory.
The GFA-5802 is well regarded for solid current delivery, a muscular, controlled presentation, and the kind of no-nonsense build that keeps older Adcom amps in demand. If it’s been serviced or at least treated carefully, this is the sort of used amp that can still anchor a serious system; just confirm stable channel balance, quiet idle behavior, and clean output, since age-related wear matters more than cosmetic niceties here.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
ADCOM emerged in the 1970s as a family-owned American audio venture founded by audiophile Newt Channin, initially focusing on exceptionally musical moving-coil phono cartridges that set it apart from typical entrants. The brand quickly pivoted to electronics with the groundbreaking GFA-1 power amplifier in 1979, delivering 200 watts per channel and robust current for demanding speakers, propelling ADCOM into prominence during the high-fidelity boom of the 1980s and 1990s.
The company built its legacy on high-performance amplifiers, including the Nelson Pass-designed GFA-555 that garnered worldwide acclaim, alongside AV tuners, preamps, and multichannel power amps like the GFA-6000 tailored for home theater. While early roots lay in phono gear, ADCOM specialized in electronics offering superior sound quality without extravagant pricing, eschewing speakers, headphones, or extensive cabling lines.
Positioned firmly in the mid-fi realm, ADCOM defined accessible high-end audio for discerning buyers, blending value and performance that rivaled pricier competitors. After challenges and ownership shifts—including a Thai firm and a faltering 2010 relaunch—the brand staged a robust comeback in 2024 under J&B Distribution, reviving classics like the GFA-555ms alongside modern integrated amps and preamps, reclaiming its spot among savvy audiophiles seeking reliable, soul-stirring sound.
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