pioneer MXA-1

After the adoption in 1961 of the standard for stereo broadcasting on FM bands, the production of equipment with decoders began. The name of the broadcasting method was adopted as MPX (from multiplex), and the working system was called "zenith-general-electric" (from the names of companies that developed almost identical systems and registered them as a common system - Zenith Electronics Corporation and General Electric). In the hands of buyers, however, there were already a large number of stereo receivers and tuners working in the multicast system and having an input / output system for cooperation with external MPX decoders. Pioneer, as a leading exporter of receivers, had to provide at least some of the buyers of the SM-Bxxx, SM-Gxxx and SM-Qxxx receivers with devices that were to enable stereo MPX reception. The company released two models of tube decoders. The first one was the matrix MXA-1A with two 6CG7 tubes (a tube electronically similar to the ECC82). Power was supplied from a 6X4 / EZ90 lamp. Apart from the MPX input and the two L and R outputs, the decoder had Mono / Stereo switches, Noise Filter, i.e. a filter that was also used later in semiconductor devices, blocking the rest of the MPX pilot signal at the output. And of course the power switch. The next model was the MXA-3, sharing the housing with its predecessor. Electronically, however, it was a completely different design. Decoding in the matrix system was provided by two tubes 6AQ8 / ECC85 and 6AN8A. The half-wave power supply used one silicon diode. The layout of inputs and outputs and switches is almost identical to its predecessor. And the main difference - the MXA-3 had a neon MPX signal indicator instead of a light bulb when the power is turned on.

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