Dynaco 400 Van Alstine Modified (1973)
One period source called the Dynaco Stereo 400 "the Tyrannosaurus Rex of power amps in 1973." It was a rugged, solidly built solid-state amplifier rated at 200 watts per channel. Factory-wired it listed at $669.00 ($769.00 with meters), or $499.00 as a kit. The meter kit was available separately for $85.00. It drew 11 amps maximum. That was serious iron for the era.
The version documented here is the Van Alstine Modified 400. Frank Van Alstine, who also produced the Van Alstine Model One preamplifier, was well known in the 1970s for modifying Dynaco components. He told the Boston Audio Society that Dynaco products were well designed but used parts that interfered with the function the designer intended. The modifications to the 400 included Van Alstine's custom amplifier circuit and boards, a modified power supply board, and the removal or disabling of several functions - including the Dynaguard circuit and the high and low filter push buttons. A later variant, the MOS-FET 400E, appeared in some listings as a 200-watt-per-channel solid-state amplifier.
How the 400 relates to Dynaco's other solid-state amps, the ST-120 and ST-150 for instance, is not clearly documented. One forum post suggests the ST-416 was a Dynaco adaptation of the Van Alstine "Double Dyna" modification to the ST-400, but that remains unconfirmed. A 1979 review in Audio Amateur found the Van Alstine-modified 400 a good amplifier but too expensive for what it was - a relatively minor modification of a moderately priced amp.
Owners generally speak well of it. One long-time user on the Klipsch forums called the 400 a "terrific amp," and said it sounded "open, clean and grain free" with LaScalas. Another reported their AVA-modified 400 sounded "awesome" until a 60Hz hum developed from the right-side assembly. A Reddit thread on the same issue attests that it is a recurring complaint. The amplifier appears to have seen hard service. One dead example surfaced after years as a mobile DJ amp, and another arrived with a dust cover cracked in shipping.
Known specifications remain thin:
- Power output: 200 watts per channel into 8Ω (stereo); 600 watts into 8Ω (mono)
- Frequency response: 20Hz to 20kHz
- Original price (1975): $669 wired, $769 with meters, $499 kit
- Power consumption: 11 amps maximum
- Country of manufacture: USA
No production years, dimensions, weight, or detailed distortion figures are documented. The Van Alstine-modified 400 remains a collector's piece for those who value the era's high-power solid-state designs and the cottage industry of modifiers that grew up around them.
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