Technics SA-8500X

Big 17kg Quad receiver produced midway from the enthusiastic 1970 launch of the first surround adventure and its discrete burying in 1977.

The SA-8500X is an updated SA-8000X : a few more functions added and, mostly, doubling up on power output !

Each amplifier's final stage is set on its own vertical card with its own heatsink plugged into the main power board - besides early LSI circuits, this was rather high-end for 1973.
Two small caps (by today's standards) smooth out the current obtained from the mid-sized (by 1973's standards) power transformer.

The SA-8500X sports a dual-gate MOS-Fet charged four-gang FM tuner with double differential switching MPX section, an integrated demodulator for CD-4 records, a "high-blend" CD-4 mode to "enhance worn out CD-4 records" (?), three tape out terminals (all ready for Quad, thus making a total of 24 RCA terminals !), two loudspeaker pairs fed by 4x 34W or 2x 85W.

Also many modes which still get a lot of us confused : Discrete (CD-4), Matrix 1 (RM), Matrix 2 and the usual mono and stereo.
The FM tuner also allows an MPX signal to be output in view of the (future) quad broadcasts to be decoded through an external processor.

But for those who really wanted an overdoZe of surround sound, the real stuff wasn't receivers but separates, such as those shown below : SH-3433 quad audioscope with 8cm CRT, SH-400 CD-4 demodulator for CD-4 records and SE-405H CD-4 demod' for high-bandwidth semi-conductor cartridges such as Technics' own EPC-405CII.

CD-4 was mainly developped by Victor Company of Japan (JVC), a brand fully owned by Matsushita since 1963.