Ortofon SL-15T
Seven grams of moving-coil, split from its transformers so it could live on any tonearm you owned.
Overview
Ortofon's earlier S-15T had a problem that had nothing to do with sound. The transformers were built into the cartridge body, and the whole assembly was too big and too heavy for the smaller tonearms of the mid-1960s. Ortofon's fix, as Audio (September 1967, p.46) explained, was to separate the transformers from the generator entirely, producing "a 7-gram peanut which will fit any tone arm, including those on automatic turntables." That made it a moving-coil that could be dropped into the arms and changers ordinary listeners owned, rather than the transcription arms that moving-coils had previously demanded.
The numbers are unusual even by moving-coil standards. Frequency response is quoted at 10-40,000 Hz, output impedance is 2 ohms, and output without transformers, loaded, is just 0.04 mV. That tiny figure is why the external transformer is a requirement and not an accessory. The matching 2-15-K step-up box takes the primary impedance of 1-5 ohms up to a 2100-ohm secondary, presenting a recommended load of 10 to 50k ohms to the preamp. With the transformers in place, Audio (September 1967, p.46) measured sensitivity at 6.2 mV at 1000 Hz on both channels, referred to 3.54 cm/sec. That is a workable figure for a tube phono stage of the period.
The stylus is a 0.7 × 0.3-mil elliptical diamond on an aluminum-tube cantilever, with a 15-degree tracking angle and a recommended force of 1-2 grams. Audio found 1.5 grams optimum for low distortion and satisfactory tracking, and reported that the SL-15T "had no difficulty tracking any commercially-made disc that we tried." Static compliance is quoted at 20 × 10⁻⁶ cm/dyne, and equivalent mass at the stylus point is 0.9 mg. The cantilever carries a smooth protective tube that contacts the record if excess downward force is accidentally applied. The owner can't replace the stylus, and that is the SL-15T's real inconvenience: a worn or misaligned stylus must go back to the distributor. Audio conceded this was "a distinct bother" but argued the fine diamond tip and protective sleeve made the trip less likely than with many other cartridges.
Channel separation is rated 20-30 dB at 1 kHz. Audio's bench work bore this out, measuring an average of 23 dB at 1000 Hz with good separation maintained at both frequency extremes. The magazine also noted a deliberate rise above 8 kHz, a resonant peak of about 4 dB. Elpa Marketing, the distributor, described it in its brochure as intentional, compensating for high-frequency loss from tracing in inner grooves. Elpa reportedly told Audio that current production had trimmed the peaks to 2 dB. The reviewer did not find the rise objectionable. A 3-dB treble cut at the preamp would even things out if desired, but in most cases it was not required.
High Fidelity (November 1967, p.73) also put the SL-15T through CBS Labs testing alongside the Ortofon RS-212 tonearm, and HiFi-Stereo (January 1968, p.42) was unreservedly enthusiastic about the pairing, noting the RS-212's anti-skating feature, hydraulically damped cueing lift, and ability to accommodate cartridges from 7 to 19 grams. The SL-15T sits at the bottom of that range — the point of the whole design.
Pricing at introduction was $75 with the elliptical stylus and the separate 2-15-K transformers, or $60 without them. Elpa's advertising positioned the SL-15T for "the better automatic turntable" at $75, with the S-15 — the version for transcription arms — at $80. That $5 gap tells you exactly who Ortofon thought this cartridge was for: the listener with a good changer, not a broadcast console.
In listening, Audio (September 1967, p.46) described the midrange as smooth, the bass line solid, and the highs clear and bright, with brass and transients reproduced particularly well. On some violin records a 3-dB high-treble cut improved the balance. The overall verdict was of "an outstanding cartridge for use in the finest stereo high fidelity systems," flawed only by minor installation inconveniences. Signal-to-noise through the transformers and a tube RIAA preamp measured 50 dB referred to 3.4 cm/sec at 1000 Hz, with hum inaudible at listening levels. Transistor preamps were expected to do better still.
For collectors, the SL-15T is one of the few moving-coils of its era that can be sensibly mounted on the automatic turntables people collect today. The catch is the same one buyers faced in 1967: no user-replaceable stylus, and the transformers are not optional. A complete example means cartridge plus the 2-15-K step-up box, because without the transformers the 0.04 mV output is essentially unusable. Original prices of $60 and $75 give a rough sense of where the market sat. Surviving examples vary enormously in stylus condition, and a re-tip or factory service is part of the ownership math.
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