Soundcraftsmen MA5002 (1979)
Two hundred fifty watts a side, VU meters glowing, and a Class H supply that only wakes up when the music demands it.
Overview
The MA5002 is a stereo power amplifier with meters, level controls, and clipping indicators across its front panel. That's a busy face for a power amp. Soundcraftsmen clearly wanted it watched as much as heard. The rated output is 250 watts RMS into 8 ohms and 380 watts into 4 ohms, per channel. Those are the numbers the company put in print in its 1979 product literature.
What makes the MA5002 interesting isn't just the wattage — it's the topology. Soundcraftsmen called it Class "H" Vari-Portional circuitry, designed for cool, efficient operation with no fans needed. The way it works, as Modern Recording (December 1977, p.72) explained in its review of the amplifier, is that a second, higher-voltage supply rail kicks in only when the signal demands more power than the primary rail can deliver. Green LEDs on the front panel light up when that extra supply comes into play. For most listening, the amp runs on the lower rail and wastes less energy as heat. That's the theory, anyway, and it's a genuinely clever one for a 1979 design.
The distortion figures are respectable for the era: IM distortion under 0.05%, THD under 0.1%, and TIM under 0.02%. Signal-to-noise is quoted at greater than 105dB down, and frequency response is given as ±¼ dB from 20Hz to 20kHz. Slew rate is listed as greater than 90V per microsecond at the supply and greater than 50V per microsecond at the amplifier, with a damping factor greater than 150 at 50Hz. Input sensitivity is 1.28V RMS for rated output.
Modern Recording (December 1977, p.73) called the MA5002 "a highly sophisticated amplifier capable of very high power output levels," though the reviewer also noted a subjective "hard" feeling to the sound that he admitted might not be shared by other listeners. That's the kind of honest caveat you don't always get in period reviews, and it's worth keeping in mind: this is a muscular, efficient amplifier, not necessarily a warm one.
Around the back, the MA5002 has ¼-inch phone jack inputs and banana terminal outputs for two pairs of speakers. It has a standard rack front panel with handles, and walnut-grained side panels are included, so it can live in a rack or on a shelf. The amp also features Auto-Crowbar protection and an LED overload indicator. Soundcraftsmen made a point of noting there's no current limiting in the design. That means the amp can deliver short-term bursts into difficult loads, and it also means the protection circuit has to do its job.
Soundcraftsmen's own advertising in Audio (November 1977, p.9) billed the MA5002 as "a $1,000 value for under $700." That's marketing copy, of course.
In the UK, the MA5002 showed up in the pages of Studio Sound throughout 1978 and 1979, listed by REW at £399.00 excluding VAT.
The MA5002 is a high-power, feature-rich amplifier from a company better known for its graphic equalizers. The same Studio Sound ads that listed the MA5002 also described Soundcraftsmen as "America's Largest Manufacturer of Graphic Equalizers." The amp was part of a broader push into electronics, and it's respected among enthusiasts who value efficient Class H designs and honest power ratings. The lack of a fan means one less thing to fail.
It suits anyone who wants serious power without the bulk and heat of a conventional Class A/B amp.
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