Heathkit W3-AM
A dual-chassis Williamson amplifier kit that put a 20-watt classic on two separate pieces of metal. The builder could stack them however the shelf allowed.
Overview
The W3-AM is the Heathkit that asked its buyer to assemble an amplifier in two halves. Heath built it as a dual-chassis design. The power supply and the amplifier stages each live on their own chassis, and the builder could mount them side by side or one above the other, depending on what the installation demanded. Heath's own catalog copy pitched this as "ideal versatility" for custom installations. It's also the detail that separates a W3-AM from the single-chassis W4-AM that appeared alongside it in the same literature.
The circuit is a Williamson. Heath's catalog text from the period is direct about it. The company credited the Williamson topology as one of the great developments in high-fidelity reproduction, and described the W3-AM as a 20-watt amplifier that kept the simplicity of the original Williamson circuit while delivering performance that many listeners considered to surpass the original. That's marketing copy, not a measurement. Heath was selling kits, and the catalog prose reads like it. The 20-watt rating and the Williamson lineage are the two facts that define the model, and both come from Heath's own published material.
The W3-AM shared catalog pages with the W-5M and W-6M, the mono amplifier kits Heath positioned above it in the line (Audiocraft, February 1958, p.12). The W-5M was offered as a 25-watt kit at $59.75 and the W-6M as a 70-watt kit at $109.95. The W-5M was pitched as the economical 25-watt entry and the W-6M as the high-power option for systems with concert-hall ambitions. The W3-AM was the low-cost amplifier of "ideal versatility," for the builder who wanted Williamson performance and the freedom to arrange the chassis to suit a custom installation. Shipping weight was listed at 29 lbs., lighter than either of its catalog companions. That fits a 20-watt design built across two smaller chassis rather than one large one.
Collectors who seek out the W3-AM today are after the late-1950s Heathkit catalog, when the Williamson circuit was still the reference point for serious home amplification and Heath was packaging it for the kit builder at a price the company described as low. The dual-chassis arrangement makes original examples something of a scavenger hunt. A complete set means both chassis, and the flexibility that made the design attractive in 1958 is the same thing that makes mismatched or incomplete pairs a hazard for buyers now. Anyone shopping for one should confirm both halves are present and that the power supply chassis hasn't been separated from its amplifier over the intervening decades.
On the evidence of Heath's own literature, the W3-AM is not a high-power amplifier. The 20-watt figure is modest even by the standards of its catalog siblings, and Heath reserved the "plenty of reserve power" language for the W-6M.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.