The SUPER high current Adcom GFA-535 II

This was a fun project!

Adcom had a sensational success with the GFA-535 in the 80s and 90s. A great bargain! For 300 bucks, you got a true dual-mono amplifier designed by Nelson Pass. (Separate power supplies for both channels.) Conservatively rated at 60WPC, with a high-current power supply, it was a lot of amp for the money. Lots of people read this glowing review at Stereophile magazine and bought one.


Continue reading The SUPER high current Adcom GFA-535 II

The A/B/X-Box challenges your assumptions about amplifiers


I’ll admit, I am biased!

Given a choice between two amplifiers, I am likely to believe that the more expensive, more powerful, and more beautiful amplifier will actually sound better and perform better.

But, this could not always be true! In real life, some moderately priced, ordinary-looking products actually outperform some so-called “high-end” products. (A term that makes me cringe a bit.)

So, how do we get at the truth? How do you compare the sound of two amplifiers?

Continue reading The A/B/X-Box challenges your assumptions about amplifiers

The Adcom GFA-555 Mark One-and-a-half.

I’ve rescued this beautiful Adcom GFA-555 Mark II from an amateurish repair attempt. Evidently, the amp blew its output transistors, (rare with these amps actually) and it was repaired with non-matching parts, and some counterfeit output transistors! These were mixed with good original transistors. This repair no doubt worked, but it blew out again shortly after.

Continue reading The Adcom GFA-555 Mark One-and-a-half.