Marantz ST-8mkII (c. 1980)
The Marantz ST-8mkII is a quartz-lock FM/AM tuner from the company's ESOTEC series. It sold in Japan around 1980 for ¥135,000. It is rare, and it looks it. The champagne-gold front panel carries a built-in oscilloscope in place of the usual signal and tuning meters. During FM reception the scope shows signal strength on the vertical axis and tuning state on the horizontal axis at the same time. It can also be connected to other components to monitor the separation characteristics of a deck or amplifier. The dial is blue-illuminated with a red pointer tip, and the glowing trace is never boring to watch.
The tuning system is the other headline feature. Marantz's disc-shaped "gyro touch" knob is linked to a quartz lock circuit. Turn the knob and the lock releases. Let go when tuning is complete and the circuit locks the frequency in 100 kHz steps. The front end uses a 5-gang FM, 3-gang AM variable capacitor. The IF stage splits into a main circuit for sound quality and a sub-circuit for multipath muting. The main section uses a 4-pole linear phase LC filter and an SQW elastic surface filter to reduce distortion, and a PLL pilot canceller in the MPX stage keeps stereo separation stable. FM numbers were serious for the era: 50 dB quieting sensitivity of 14.1 dBf in mono (2.8 µV) and 34.2 dBf in stereo (28 µV), signal-to-noise of 88 dB mono and 80 dB stereo, and stereo separation of 55 dB at 1 kHz.
The unit was originally sold in a wooden case without a metal lid, like the companion PM-8 amplifier. The metal lid was a separate option. The AM section covers 531-1602 kHz, which reflects the Japanese AM frequency reassignment of November 1978. The tuner weighs 10.3 kg, measures 474 × 172 × 335 mm, and draws 30W.
Little is documented about the precise differences between the ST-8 and the ST-8mkII. Sources note no visible differences in appearance, and the AM band range and wood case may be the key changes. The related ST-8 was produced from 1980-82, and the mkII appears to have succeeded it shortly after, but no explicit production years for the mkII itself have been confirmed. The scope lamp is a known weak point. At least one auction listing noted the display could not be confirmed even though the lamp lit faintly. European auction data from 2009-2022 shows prices from roughly €540 to €2,199, with units that include the wood case, manual, and good photos commanding a premium. Audio Database (accessed 2025) provides the most complete technical record of this model.
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