API 500-B4 (c. 1989–1990)
A four-slot lunchbox built for the engineer who wanted the console in a carry-on.
Overview
The 500-B4 is a portable rack for API's modular 500-series processors. API's own advertising from the period put it in the plainest terms: a rack for the traveling engineer or musician. That is the right pitch. You don't buy this for its faceplate. It is a frame, four slots of API modular hardware in a chassis you can put under an arm. In the late 1980s that idea was new enough that API had to explain the concept in a magazine ad rather than assume the reader already owned three of them.
The period advertising ran repeatedly through Mix in 1989 and 1990. It presented the 500-B4 alongside the modules it was built to hold: the 512b mic pre, an all-discrete mic preamp and instrument direct box in a single slot, and the 550b EQ, which API described as carrying the same circuit as the all-discrete 550A but with four bands and more frequencies. Those two modules are the reason the rack exists. A traveling engineer could carry four channels of API preamplification, or two pres and two EQs, in a package that fit in a road case instead of a console footprint. The rack is the least glamorous of the three, and it is the one that made the other two portable.
The 500-B4 is not a processor, and this trips up buyers constantly. It has no audio character of its own. Every sound that comes out of it comes from the modules in the slots. The 500-series format has since grown into a whole ecosystem, and the 500-B4 is the specific chassis API was selling when the format was still young. It is the four-slot lunchbox API was advertising in the 1989-1991 window, distinct from the 10-slot 500V rack and the two-slot 500H that also appear in the same period literature. The naming is inconsistent across sources. The hyphenated 500-B4 and the unhyphenated 500B4 both turn up, and the 1999 Studio Sound reissue coverage calls it the "500b4 (4-slot lunchbox with PSU)." Same rack, different typography.
The power supply is built in, which separates the 500-B4 from a passive frame. API's later coverage of the reissued 500-series line describes the 500H as a two-slot rack with PSU, the 500b4 as a four-slot lunchbox with PSU, and the 500V as a ten-slot rack with outboard power. The 500-B4 sits in the middle: enough slots to build a small front-end, with the supply onboard so there is no separate box to lose.
The 500-B4 was an enabler rather than a landmark. It shows up in the same breath as the 512b and 550b because it was sold to hold them. API's advertising in that stretch - Mix (April 1990, p.23) ran the same copy pairing the rack with the 512b mic pre and 550b EQ - treats the three as a system rather than as separate products. The 500-B4 is a chassis.
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Related Models
- API 212A
- API 2448
- API 2500 (2002–Present)
- API 500-series (1969–Present)
- API 535A