Harman Kardon Rabco ST-7

The Rabco ST-7 is a tangential-tracking turntable, sold under the Harman Kardon name after the company took on the Rabco line. It was an improved update of the earlier SL-8E. The idea is simple. A pivoted arm swings in an arc across the record. This tonearm tracks straight from the outer edge to the label, following the same path the cutting head took when the master was made. That eliminates tracking error and skating force entirely - the "cascade of zeroes" Harman Kardon's own advertising leaned on heavily in 1975 and 1976. High Fidelity (September 1975, p.19) ran the same promotional copy, which claimed zero tracking error, zero skating force, and zero stylus overhang.

It's a belt-drive table with a servo-controlled DC motor spinning a 12-inch, 1.4 kg aluminum die-cast platter. The low-mass tubular tonearm has an effective mass of 6g and adjustable stylus force from 0.5 to 3g, with a cueing lever for raising and lowering the arm. Wow and flutter is rated at 0.05% WRMS. The output is described as "practically flat" from 20Hz to 20kHz plus the RIAA curve, though no ±dB figure is documented.

The ST-7 was designed to be simple and easy to use, and it generally was. Dimensions are 455 × 145 × 400 mm, and it weighs 10.5 kg.

Production years and original price aren't documented in the record. The design history is a little tangled. Rabco built the tangential-tracking concept, and Harman Kardon distributed and eventually absorbed the line, which is why the table shows up under both names. The ST-7 is the mature version of that concept, from before the format faded from the mainstream.