Yamaha SPX 90
Not much is documented about the Yamaha SPX 90 in the material that has been verified. The record does show a rackmount digital signal processor used widely in professional studios and live rigs through the late 1980s and into the 1990s. It turns up again and again in period studio gear lists, usually alongside the bigger Yamaha REV-series reverbs and its own successors, the SPX 90 II, SPX 900, and SPX 1000.
What can be said with confidence comes mostly from where the unit appears, not from a spec sheet. A 1991 studio equipment list places the SPX 90 in the onstage signal processing rack of a touring setup. Another from the same era lists it among the house reverbs next to a Yamaha REV-1, REV-7, and Roland SRV-2000. A third studio inventory pairs it with an AMS RMX-16 and EMT-140. It was a working processor, the kind of box engineers reached for by default.
Yamaha's own advertising from the period pitched it as a creative tool at a credible price. A Mix advertisement (1987, p.35) said the SPX 90 added creativity for the player or home recordist at a very credible price. It also noted that the effects could be actuated by a change in input level during performance, a hint at the envelope-following and trigger capabilities that set it apart from simpler reverb boxes. According to Mix (1987, p.35), the SPX 90 could add creativity to a home recording enthusiast's music at a very credible price. The same ad copy ran in Mix later that year (p.19).
Beyond that, the surviving record is thin. There is no verified original retail price for the SPX 90 itself, no confirmed production years, and no detailed specification list. The lineage is clearer. The SPX 1000, described in a contemporary manual as "this modern, single-rack-space update of the original SPX 90," carried 40 factory presets and 59 user RAM locations, 16-bit stereo sampling at 44.1 kHz, and a $1,595 retail price. That makes the SPX 90 the ancestor of a fairly serious line, but it doesn't say what the 90 itself cost or contained.
If you own one or have documentation, that's the kind of gap this archive exists to fill.
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