Soundcraftsmen A5002
A 250-watt-per-channel amp that stays calm when the load turns ugly, thanks to Class-H rails and a crowbar that refuses to current-limit.
Overview
The A5002 makes its case with the spec sheet rather than the styling. Soundcraftsmen rated it at 250 watts per channel into 8 ohms and 375 watts into 4 ohms, continuous RMS, 20 to 20,000 Hz, at no more than 0.09% THD. Those are full-bandwidth numbers, and the 4-ohm figure tells you this is a supply built to deliver current rather than just voltage.
The A5002 uses Class-H "Vari-Proportional" circuitry paired with Soundcraftsmen's Autobuffer, which the company specified for continuous operation into 2 ohms. The amp tracks the signal and raises its rail voltage only when the music demands it, so it runs cooler and more efficiently at normal listening levels while still having reserve for the peaks. The protection is an auto crowbar circuit that guards the output without resorting to current limiting. The A5002 is meant to keep delivering into low impedances rather than fold back the moment things get hard. Contemporary Soundcraftsmen literature framed the Class-H topology as setting a new benchmark for high-power stereo amplifier design. That is marketing talking, but the underlying engineering claim is real enough.
Power metering is reported inconsistently in manufacturer documents - some cite 20 LEDs per channel while others cite 40 LEDs - with a 0-1,000 watt scale calibrated at 4 ohms with ±3 dB accuracy. There are also true clipping indicators for each channel and input level controls. Front-panel switching for two pairs of speakers means you can run two sets without crawling behind the rack. The chassis measures 19 inches wide, 7 inches tall, and 12 inches deep, and it weighs 50 pounds. Most of that is transformer and heatsink. Buyers who wanted the same amplifier without the meters or level controls could step to the A5001, which Soundcraftsmen sold as the A5002 minus those front-panel features at the same 50 pounds.
The electrical numbers are good: signal-to-noise ratio above 105 dB, slew rate greater than 50 V/microsecond, and transient intermodulation distortion below 0.02%. The high S/N figure matters, since a 250-wpc amp with a noisy front end would be unusable on efficient speakers. The 0.09% THD rating is modest by modern standards but respectable for a high-power amp of its day, and the TIM figure suggests the designers cared about the kind of distortion that colors the sound rather than chasing a single headline number.
Audio (October 1989, p.95) described the A5002's Class-H circuitry as establishing a new standard for high-power amplifier technology, and singled out the non-current-limited output as a design virtue — the sort of continuous delivery that avoids the heat buildup and distortion that plague amps forced to current-limit into hard loads. That is a period publication giving the topology its due, and it lines up with what the spec sheet claims. Earlier Soundcraftsmen advertising for the related MA5002 pitched the Class-H concept as a cost-conscious engineering achievement, and the A5002 carried that same design philosophy forward into the late 1980s.
The A5002 is not a glamorous amp, and it does not pretend to be. It offers a documented 250/375-watt power plant with a protection scheme built for real-world speakers, useful metering, and a 50-pound chassis. Anyone shopping one should confirm the crowbar circuit is intact and the input level controls are not scratchy, since those are the parts that see wear. Plan on a serious shelf, too, because 50 pounds of amplifier does not sit politely on a bookshelf.
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