One of the best stereo amplifiers of it's time. A Nelson Pass design that proved an affordable amplifier could offer the power and sound quality of audiophile amps costing 5 times as much.
High power and high current design that can take your speakers to the next level. Great soundstage and detail from an amp that can drive speakers with even the most difficult loads to levels that most amps cannot handle. This particular piece is electronically sound, but as you can see, has some slight discoloration to the anodized faceplate.
Inputs 100k Ω. Two gold-plated, Teflon-insulted brass RCA jacks. They are close enough together to make connection a breeze.
Gain 27 dB.
Input Sensitivity 1.75V for 200 W into 8 Ω. 130 mV for 1 W into 8 Ω.
Rated Power Output 200 watts per channel into 8 Ω from 20 - 20,000 Hz at less than 0.04% THD, both channels driven. 325 watts per channel into 4 Ω from 20 - 20,000 Hz at less than 0.04% THD, both channels driven (requires fan option to do this for any length of time). 600 watts into 8 Ω from 20 - 20,000 Hz at less than 0.04% THD, bridged mono (requires fan option to do this for any length of time). 850 watts into 4 Ω from 20 - 20,000 Hz at less than 0.09% THD, bridged mono (requires fan option to do this for any length of time).
Dynamic Headroom 2.5 dB at 4 Ω.
Power Bandwidth 1.7 - 100,000 Hz at - 3 dB.
Frequency Response 10 - 20,000 Hz +0, -0.25 dB at 1 W RMS into 8 Ω.
Damping Factor Not less than 800 from 20 - 20,000 Hz into 8 Ω.
Noise Not less than -110dB down from 200 watts into 8 Ω, A-weighted.
Power Input 120 VAC 50-60 Hz. 72 VA idle. 1,500 VA maximum. 675 VA at 200 W into 8 Ω.
I measure 37.5 watts at idle, cold. 60 watts at idle, warm (0.73A). 92 Watts (1.09A) when delivering 1 watt per channel into 8 Ω. 845 watts when delivering 265 watts per channel into 8 Ω.
It draws zero power when turned off because it has a real power switch. It's not like modern equipment that never really turns off and consumes power and remains a fire hazard any time its plugged in. The GFA-555 II is completely disconnected when switched off.
Size Chassis: 6-3/4 x 17 x 12-3/16 inches (172 x 432 x 310 mm) HWD. Overall: 7-1/4 x 17 x 12-3/16 inches (185 x 432 x 310 mm) HWD.
Weight 35 pounds (16 kg). 39 pounds (18 kg), packed.
Quality Made in USA.