The Adcom GFA was designed for Adcom by Nelson Pass leveraging the International Rectifier HexFet T03 output devices. Nelson Pass designed these. I am considering changing(up grading)to Adcom GFA amp and GFP pre. I currently am using a Parasound HCAa and. ADCOM GFA – Power amplifier overview and full product specs on CNET.
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Minimalist in circuit design, with only three gain stages, but maximalist in execution.
Adcom GFA-5802 2 Channel Power Amplifier
They have a wonderfully flat curve if they are biased heavily enough. The heat ages the capacitors prematurely, so I have installed high-endurance C types throughout. In particular, the uF 16V power-supply filters for the high-voltage supply are known to die and cause a loss of bass response.
These should hold up much better. Also, the gfa-58022 cube is a new power relay, rated at 16A versus the original 12A. I always replace power switches and relays just in case they are corroded over time. Here are the input boards, which contain the RCA and XLR input connectors, along with the circuitry for the first stage of the amp.
Adcom GFA 2 Channel Power Amplifier | eBay
These were found to be off gfa-58022 quite a lot, perhaps due to heat stress. Fortunately, these devices are still available, so I bought of them, built a jig to match them, and sorted out pairs that match to less than 1mV.
Two of these mosfets had actually lost some gain, possibly due to heat stress, so I replaced them.
The symptom was that I needed to turn the DC bias pot all the way to one side to get it to zero. Notice the pin-connector on the RCA input! Acdom would be ironic to use fancy, expensive RCA cables, when there is this weedy little push-pin connector on the inside.
Like a motor with a huge flywheel.
Smooth sounds came out of the accom monitors. Hooked to my subwoofer, it was utterly unconcerned with the large current demands, and delivered tight, effortless bass as a matter-of-fact.
Some notes about restoring a GFA-5802
Nice quality fiberglass through-holes. I measured WPC with both channels driven into 8 ohms, just before clipping. Previous Post Sneak preview: Leave a Reply Cancel reply.