Sonus Blue (c. 1976–1979)
The Sonus Blue Label is a phono cartridge that turns up in period reviews from 1976 through 1979. High Fidelity (September 1976, p.51) said the Sonus Green, Red, and Blue were really a single cartridge body with different stylus assemblies - spherical for the Green, elliptical for the Red, and a "Multiradial" for the Blue. That makes the line a closer family than most.
Audio (April 1977, p.70) published the manufacturer's specifications for the Blue Label: frequency response 5 Hz to 20 kHz ±1.5 dB, voltage output 0.8 mV at 1 kHz/cm/sec, nominal channel separation 30 dB at 1 kHz, and a recommended load of 47 kilohms in parallel with no more than 400 pF. HI-Fi-Stereo-Buyers (August 1976, p.30) tested the Blue and Red together. They found the stylus mass about as low as that of almost any magnetic cartridge they knew. Response on a CBS STR 100 record stayed within ±1 dB from 40 Hz to 12.5 kHz, rising a few decibels at 20 kHz. Separation measured roughly 20 dB in the midrange and 25-30 dB elsewhere.
By July 1979 the Blue Label appeared in Sonus's Gold Series II line. Audio (July 1979, p.79) repeated the 47 kilohm / 400 pF loading note and singled out the Blue Label stylus as the one intended for CD-4 records. Beyond those period reviews, documentation in the archive is thin. No production dates, original list price, or collector-market data has surfaced.
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