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The Stereo 400 Series II has a strong place in Dynaco’s lineup: a relatively compact, high-power solid-state amplifier known for its clean, forceful presentation and roughly 200 watts per channel into 8 ohms. At A$531, this looks like a good buy rather than merely fair value—below the A$637 median and comfortably above the A$315 lower quartile in the 66-listing comparison, putting it in the attractive part of the market.
Its appeal is straightforward: substantial headroom, robust construction, and enough power for demanding speakers without resorting to modern, bulky hardware. The price leaves some room for sensible servicing, which matters with an amplifier of this age; intermittent speaker relays, heat-stressed power-supply components, worn fuse holders, and tired solder joints are known service points. Confirm both channels, relay operation, quietness, meters, and stable output before paying, but a working example at A$531 is a worthwhile opportunity.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
Dynaco emerged in 1955 from Philadelphia, Pennsylvania, when hi-fi pioneer David Hafler partnered with engineer Ed Laurent to form the Dyna Company. Hafler brought expertise from his earlier Acrosound venture, which produced high-quality output transformers starting in 1950. The duo targeted the burgeoning hi-fi market with affordable, DIY-friendly kits, launching the Mk II 50-watt tube amplifier shortly after incorporation and relocating to a former chocolate factory for expanded operations.
The brand specialized in tube amplifiers that defined its legacy, including the iconic Stereo 70—over 350,000 units sold—alongside models like the Mk III. Dynaco expanded into FM tuners such as the FM-1, bookshelf speakers like the A-25, solid-state amps, and innovative systems like the Dynaquad for simulated four-channel sound. Late-1970s efforts included the Phase III speakers, though the company shifted toward kits and components emphasizing value and performance.
Dynaco holds a revered position as the era's top-selling tube amp maker, beloved by budget-conscious audiophiles for reliable, high-value hi-fi. Liquidated in 1980 after Hafler's sale to a toy firm, its vintage gear remains a collector's staple, with later revivals by Panor Corporation producing replicas for tube enthusiasts seeking that classic warmth and build-it-yourself appeal.
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