Friday, February 4, 2011


The GFA-1 was the product that put Adcom on the map. I can't tell you exactly when it was introduced, but I believe it was the late seventies. I think I'm write because the manual has a section titled 'If You Disco', that suggests contacting the factory for information about a modification (probably to the cooling fan) for disco spund reinforcement applications. The amp employs what Adcom calls a balanced bridge design. Each channel uses two 50 watt/channel amps (one for the positive side of the waveform, one for the negative) bridged to deliver 200 watts/channel into 8 ohms, 350 into 4 ohms. Apparently the fan is noisy, so the previous owner added a crudely installed, outside the case light dimmer pot to vary the fan speed. With help from an excellent technician, who's a good friend of the blog, the fan has been disconnected. It ran for over 4 hours last night, and went to sleep listening to John Coltrane. This morning, the power LED was off, and the amp felt warm. The thermal protection circuit did it's job, and it's all fine, but I may look into replacing the fan with a newer one that will run silently. The design is compact, but very heavy (I'd guess 25-30 lbs). I've been using it to drive the DCM Timewidows and Pioneer HPM-100s, and it sounds great. I'll tell you more soon.

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