Universal Audio Model 565 "Little Dipper" Filter Set
Two continuously tunable notch/pass filters, a lo-pass and a hi-pass, all in one box. Studios reached for it when a track was drowning in hum, whistles, and camera noise.
Overview
The Model 565 doesn't look like much on a rack shelf, but the feature list is a long one: two variable-width notch/pass filters, a lo-pass filter, and a hi-pass filter, all continuously tunable, with zero insertion loss or 20 dB of gain available. That combination is why the unit earned its "Little Dipper" nickname. It dips out the offending frequencies without dragging the rest of the signal down with them.
The 565 was built to clean up tracks recorded under less-than-ideal conditions. Universal Audio's own advertising billed it as the fix for problem tracks made under adverse conditions - remote pickup, location filming, the sessions where you don't get a second take. Whistles, heterodynes, hum, and other coherent sound could be filtered out, according to the manufacturer's copy, with no audible effect on the quality of the music or voice. Semi-coherent noise, like motion picture camera noise and fluorescent fixture buzz, could be greatly reduced. So could the incoherent noise of jet aircraft, noisy amplifiers, and general background noise.
That's marketing, of course, and the claims should be read as such. But the underlying architecture is what makes the 565 interesting: two independent notch/pass filters that can be tuned and width-adjusted, which means a user could, in theory, notch out two separate offending frequencies simultaneously. Universal Audio's literature explicitly lists "simultaneous elimination of any two audio frequencies" as one of the unit's capabilities, alongside harmonic distortion filtering and wave analysis.
The 565 also found use as an effects box. Universal Audio's own materials note that it could be used for "phasing" and other unique effects, and for sharp enhancement of any audio frequency.
DB Magazine (September 1971, p.11) ran the "Little Dipper" advertisement alongside coverage of the Audio Engineering Society's 41st Technical Meeting and Exhibition, positioning the 565 as a tool for the working engineer rather than the home hobbyist. The same publication (June 1972, p.14) carried the ad again, this time with the price line reading "for less than $500" — a figure that puts the 565 squarely in the professional-but-not-exotic tier of studio outboard. Recording Engineer (August 1971, p.7) also ran the "Little Dipper" advertisement, and the unit turns up again in the pages of Recording Engineer (February 1977, p.7) in the context of a UREI-associated session on sound system electronics — a reminder that the 565 was part of the broader UREI ecosystem of studio gear.
If you're trying to date a unit, the 565 advertisements that ran in DB Magazine and Recording Engineer in the early 1970s were placed by UREI, with the company address listed as 11922 Valerio Street, North Hollywood, California. The "UREI quality, of course" tagline appears in at least one version of the ad, and the export agent is listed as Gotham Export Corporation in New York. Collectors will often find UREI branding on the faceplate rather than Universal Audio, even though the literature attributes the product to Universal Audio.
The feature set is unusual for a filter box of the period. Most competing units offered either a fixed-frequency notch or a simple high-pass/low-pass pair. The 565's two variable-width notch/pass filters, combined with the lo-pass and hi-pass sections, gave the user four separate filtering tools in a single chassis. The "zero insertion loss or 20 dB gain" spec is the other headline number. The 565 could go into a signal chain without the level drop that plagues passive filter designs, and it could add 20 dB of gain if needed. That makes it usable as a line-level gain stage in a pinch.
The "extremely low noise and distortion" claim in the manufacturer's literature is harder to verify without bench measurements. It is consistent with the intended use, since a filter that adds its own noise floor is useless for cleaning up a noisy track. Whether a given 565 meets that claim today would have to be assessed unit by unit, given the age of the components.
The 565 is not a compressor or an EQ in the conventional sense, and it doesn't have the instant-recognition appeal of a UREI 1176 or an LA-2A. It is useful outboard for archival transfers, restoration, or any signal that needs surgical frequency removal. It was advertised for "less than $500" in 1972, a not-insignificant sum at the time, which suggests it was aimed at professional facilities rather than home studios.
Universal Audio's catalog included problem-solver tools like the 565 that addressed specific, practical needs in the recording chain, not only the famous compressors. It does a specific job that few other units of its era could do as flexibly.
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