Fisher TX-420 (1971–1972)
A quadraphonic converter with a built-in eight-track player and two rear-channel amps. Fisher's bid to sell four-channel sound to people who already owned a stereo.
Overview
The TX-420 sits in a strange, specific corner of the early quad era. It is not a receiver and not a standalone tape deck. Fisher billed it as a converter, a box that turns an existing two-channel system into four-channel sound by adding two speakers and a rear-channel amplifier. The unusual part is that Fisher built the rear amps and the eight-track player into the same chassis. High Fidelity (August 1971, p.2) described the arrangement plainly: the TX-420 supplies the two channels of amplification needed to make the jump from two channels to four, along with the input and output facilities and the controls to run it all.
The eight-track player is the reason the TX-420 exists at all. Fisher and RCA had jointly announced their entry into four-channel cartridge hardware, and the TX-420 was the more ambitious of the two products. The CP-100 was the same player without amplification. The TX-420 added the two 15-watt rear amps for another $130. The same report was candid about the format's weakness. Cartridge tape hiss, doubled across front and rear channels, was "nigh impossible to live with," and the writer argued four-channel cartridges needed Dolby as badly as cassettes did.
When a four-channel tape is playing, the front-channel outputs feed the existing stereo amp through its aux, tuner, or tape inputs, while the rear-channel signals pass through the TX-420's own controls and amplifiers to the rear speakers. The magazine confirmed the 15-watt rms rating for each rear-channel amp and the $299.95 price. For two-channel sources, the unit synthesizes a rear signal from the difference information in the recording — the reflected, ambient content — and feeds it to the back channels, a matrix approach that High Fidelity (August 1971, p.2) described as enhancing the stereo effect.
That same High Fidelity notice flagged one nice detail. The bass and treble controls are of the Baxandall variety, which the magazine noted cost a little more to include than the tone-control circuits many other manufacturers used, but were worth it.
The TX-420 is tied to a format that died, four-channel eight-track, and its value today is as much as a curiosity and a working eight-track player as it is as a quad decoder. The rear amps are only 15 watts, so it wants efficient speakers behind you. The eight-track mechanism is the usual maintenance concern on any cartridge deck of this age. The format's inherent hiss is baked into the design, not a fault you can repair away. Original price was $299.95, which in 1971 bought a lot of receiver. Buyers were paying for the novelty of four channels and the convenience of an integrated player. Examples turn up, but a fully working one with a clean transport is the one to hold out for.
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