Need help?Do you have a question about the Adcom GFA-5500 and is the answer not in the manual?
Covers warnings about electric shock, water, ventilation, heat, and proper servicing.
Details on polarized plugs, extension cords, and preventing blade exposure.
Guide for connecting loudspeakers to binding posts for correct polarity and stereo imaging.
Instructions and warnings for checking and replacing the AC power fuse.
Explains the THERMAL PROTECTION LEDs and their activation conditions.
Details on the EXTERNAL PROTECTION FUSES and their replacement.
Detailed technical specs like power rating, distortion, frequency response, etc.
The ADCOM GFA-5500 is a high-current stereo power amplifier designed to deliver accurate and musical sound reproduction. It incorporates several features aimed at enhancing performance, reliability, and ease of use.
The GFA-5500 serves as a high-current power amplifier, taking a low-level audio signal from a preamplifier or tuner-preamplifier and amplifying it to drive loudspeakers. Its design emphasizes high current capability to handle demanding loudspeaker loads and deliver robust, dynamic sound. The amplifier is equipped with protection circuits to safeguard both the unit itself and connected loudspeakers from potential damage due to abnormal operating conditions.
To optimize the performance and longevity of the GFA-5500, several usage guidelines are provided. The amplifier features precision-matched MOSFETs throughout the signal path and a substantial power supply filter capacitance (80,000 µF with low ESR) for greater reserve capacity, ensuring stable and powerful output. A custom toroidal power transformer contributes to better regulation and greater peak current capability. The low number of gain stages is intended to improve signal reproduction accuracy.
For connectivity, the GFA-5500 uses high-quality, gold-plated binding posts for loudspeaker connections, accommodating bare wire, tinned wire, terminal pins, spade lugs, or banana plugs (both single and dual). These terminals are color-coded (RED for positive, BLACK for negative) to ensure correct stereo phasing. Input connections are made via gold-plated, brass RCA jacks with Teflon insulators, designed to minimize high-frequency losses and noise. The input impedance is 49.9k ohms, optimized for use with low output impedance source components like ADCOM preamplifiers.
The amplifier includes independent thermal overload and distortion LEDs for each channel. The "INSTANTANEOUS DISTORTION ALERT" LEDs light up when distortion reaches 1%, serving as a warning that the amplifier is approaching its maximum power output. Occasional flickering during high-volume listening, especially with low impedances, is normal, but continuous bright illumination indicates overdriving and suggests reducing the volume to prevent potential damage to the amplifier or loudspeakers. The "THERMAL PROTECTION" LEDs illuminate if a heatsink's temperature reaches 85°C, indicating that the amplifier has shut down to protect its amplification devices. Once the temperature returns to a safe level, the amplifier will automatically resume operation. If these protection circuits are frequently triggered, it suggests the amplifier is being overdriven or the loudspeaker load impedance is unreasonably low.
The GFA-5500 is designed to drive loudspeakers with nominal impedances down to 4 ohms without difficulty. Even systems with impedance drops to 2 ohms or less can be driven, provided excessive volume levels are avoided. For driving multiple sets of loudspeakers, an ADCOM speaker selector is recommended to ensure impedance protection.
The AC power fuse protects the electronic circuits from overloads. If the "POWER LED" does not glow when the amplifier is turned on, the AC power fuse may be blown and should be replaced with an identical type and value. However, if the fuse blows immediately after replacement, it indicates an internal problem requiring professional service. The AC ON/OFF switch controls power to the transformer circuits, with the POWER LED indicating when the amplifier is energized.
Proper installation and ventilation are crucial for the GFA-5500's long-term, trouble-free operation. The external heatsinks will become warm during normal operation and much warmer during high-level playback into low impedances. Therefore, the amplifier should be kept away from external heat sources and placed in a location that allows adequate air circulation. If mounted in an enclosed cabinet, the cabinet should have ventilation openings at the top and bottom. The top and bottom panels of the amplifier chassis also have vents that must not be obstructed. Stacking other components on top of the GFA-5500 is not recommended, especially with low-impedance loudspeakers or high-volume demands, as it can obstruct airflow and affect performance.
Regular cleaning is recommended to prevent the buildup of dust. The chassis, heatsinks, panels, and ventilating slots should be occasionally vacuumed. The front panel, top, or sides can be cleaned with a soft, lint-free cloth slightly dampened with a mild detergent solution or glass cleaner. It is important not to spray or pour liquids directly onto the amplifier.
For optimal sound quality, high-quality, low-loss, low-capacitance cables should be used for all input and output signal connections. For loudspeaker cables, the correct type and size of wire are important to avoid power loss and maintain damping factor. For runs up to 12 feet, AWG18 stranded wire is suitable; for runs up to 40 feet, AWG16 is recommended; and for runs over 40 feet, AWG14 or heavier (e.g., AWG12) should be used. Cables with low capacitance (less than 100 pF) are particularly important for long runs between the preamplifier and amplifier.
When connecting wires to the binding posts, "tinning" the wires with good quality electronic solder is recommended to minimize contact resistance. Banana plugs are preferred for their secure connection and self-cleaning action. If using bare or tinned wire, or terminal pins, they should be inserted through the hole in the binding post stud, and the insulated head should be hand-tightened clockwise. Pliers or other tools should not be used to avoid damaging the binding post assembly.
The GFA-5500 is designed with no user-serviceable parts inside. Any servicing, including checking or replacing internal components, should be referred to qualified, ADCOM-authorized service personnel. Attempting to service the unit yourself can expose you to lethal voltages, create a fire hazard, and void the warranty. In case of difficulty, ADCOM's Technical Service Department can provide assistance and direct you to an authorized repair agency if needed. If the unit needs to be returned for service, it must be shipped in its original carton and fillers, with prior authorization from ADCOM, and sent prepaid via UPS or other approved carrier.
General| Impedance | 8 Ω |
|---|---|
| Audio output channels | 2.0 channels |
| Connectivity technology | Wired |
| Product color | Black |
| Power requirements | 115 V, 50/60 Hz |
| Power consumption (typical) | 1440 W |
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