UREI 539 (year not documented)
Documentation on the UREI 539 is thin. The most concrete record is a period product listing in Modern Recording (August 1985, p.46). It describes the 539 as a room equalization filter set. It is a 27-band, cut-only unit with minimum-phase true LC networks for smooth combining response. It has a 12 dB/octave high-pass band-end filter and a low-pass band-end filter switchable between 6 and 12 dB/octave. List price then was $1,046.
Known specs from that listing:
- 27-band room equalization filter set, cut only
- Minimum-phase true LC filter networks
- 12 dB/octave high-pass band-end filter
- 6 or 12 dB/octave low-pass band-end filter
- List price: $1,046 (1985)
Beyond the listing, almost nothing is recorded. No manual, no measured review and no production dates appear in the surviving record. UREI's own advertising of the period placed its equalizers in professional studio, sound-reinforcement, and broadcast production work (Recording Engineer, October 1980, p.41), and the 539 was clearly aimed at that market. Its specific circuits, controls, and application details are largely undocumented.
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