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This preamp has been tested and works great.The Adcom GFP-555 II is a high-quality stereo preamplifier known for its excellent specifications, including a frequency response of 5 Hz to 85 kHz and a total harmonic distortion of just 0.003%.It features an input sensitivity of 2.3 mV for moving magnet (MM) and 200 mV for line inputs, with a signal-to-noise ratio of 90 dB for MM and 100 dB for line inputs. Specifications Overview: Frequency Response — The preamp operates from 5 Hz to 85 kHz, ensuring a wide range of audio reproduction. Total Harmonic Distortion — It boasts a low total harmonic distortion of 0.003%, contributing to clear sound quality. Input Sensitivity — The input sensitivity is 2.3 mV for MM and 200 mV for line inputs, allowing compatibility with various audio sources. Signal-to-Noise Ratio — The signal-to-noise ratio is 90 dB for MM and 100 dB for line inputs, indicating minimal background noise.
Condition is unknown, so at US$400 this lands below the US$441 25th percentile and well under the US$481 median, which makes it a strong buy rather than a merely fair one. For a GFP-555II, that’s a healthy entry point if the unit is complete and functioning; you’re paying less than the going middle of the market with room left for any maintenance or a basic refresh.
This preamp is well-liked for clean, neutral line-level performance, a usable phono stage, and the sort of flexible everyday control that makes Adcom gear easy to live with. The upside here is value: at this price, a tidy, original, well-kept example is worth grabbing. I’d only hesitate if the seller can’t confirm basic operation, because age-related switch, pot, and capacitor issues are the main things to check on an older preamp.
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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