Audio-Technica AT-15 (c. 1974–1978)
A CD-4 quadraphonic cartridge that the magazines liked more than the format did.
Overview
The AT-15 is a mid-1970s Audio-Technica cartridge that survives mostly as a paper trail. It's a magnetic phono cartridge built for the CD-4 Quadradisc format, fitted with a Shibata diamond stylus, and dated approximately 1974 to 1978. Treat that window as a bracket, not a birth certificate. Official documentation is thin. The period press is the record that matters, and there the AT-15 did better than most of its contemporaries.
High Fidelity (December 1974, p.53) ran it under the headline "Audio-Technica's 'Almost Best' Pickup" — a wry bit of framing that says as much about Audio-Technica's own positioning as it does about the cartridge. The magazine measured a high-frequency resonance at about 45 kHz and found square-wave curves with no significant ringing, which is the kind of result that separates a competent CD-4 design from a merely CD-4-labeled one. The AT-15 was designed for flat response into the standard 47,000-ohm phono input; measured into the 100,000-ohm CD-4 standard of the day, response came in at +1.5, −1 dB on the left channel and +0.75, −1 dB on the right, from 20 Hz to 20 kHz, with a slight top-end rise that typical CD-4 demodulators would largely cancel. That last detail is worth pausing on — it's a design that anticipated the demodulator's own behavior rather than treating the cartridge as a standalone component.
Four years later, HI-Fi-Stereo-Buyers (May 1978, p.75) put the AT-15 on its own test bench. Frequency response came back within ±2 dB from 20 Hz to 20 kHz, channel balance better than 1 dB, and worst-case stereo separation 26 dB at 1 kHz and 21 dB at 15 kHz. The two frequency-response figures don't line up exactly, probably because of different loads and test conditions, but both describe a cartridge that behaved itself across the audible band. The 1978 listening panel called it exceptionally "sweet," then added that it might prove unsuitable for the distortions of acid and punk rock.
Key Features
Shubata Stylus for CD-4 Quadradisc
The AT-15's headline feature is its Shibata diamond stylus, cut specifically to read the high-frequency carrier signal that CD-4 Quadradisc records encoded in the groove wall. CD-4 was the most demanding of the 1970s quadraphonic formats. It required a stylus with a line-contact profile and a cartridge with real bandwidth out to 45 kHz, and the Shibata was Audio-Technica's answer. The High Fidelity measurement of resonance at about 45 kHz is the number that mattered. It put the AT-15's electrical behavior well above the audio band where the CD-4 carrier lived.
Dual Load Behavior: 47 kΩ and 100 kΩ
Most phono cartridges of the era were designed around the standard 47,000-ohm moving-magnet load and left it at that. The AT-15 was designed for flat response into that load, but its CD-4 role meant it also had to work into the 100,000-ohm standard that quadraphonic demodulators presented. High Fidelity's test documents both behaviors. The slight top-end rise measured into the higher load was, per the review, largely canceled by typical CD-4 demodulators.
Elliptical and Shibata Variants
The AT-15 name covered more than one stylus profile. DaCapo Audio, which supplies replacement styli for the line, describes "the elliptical AT-15 variants" alongside "the Shibata versions." That means the AT-15E, AT-15Ea, and AT-15XE designations refer to elliptical-stylus versions of the same basic cartridge, and the sources distinguish only between elliptical and Shibata versions. The AT-15EA/G appears in marketplace listings described as an MM cartridge, sold mounted on an Audio-Technica-branded headshell with the original ATN-15Ea stylus. Be careful with the suffixes. The AT-15S stylus page from My Needle Store lists a 0.3 × 0.7 mil elliptical tip and 1-1.5 grams tracking pressure, but that's a spec for the AT-15S stylus specifically, not for every AT-15 variant.
Square-Wave Behavior and Separation
Square-wave testing exposes a cartridge's phase behavior, and High Fidelity's finding of "no significant ringing" is a meaningful result for a design pushing bandwidth toward 45 kHz. The 1978 HI-Fi-Stereo-Buyers separation figures, 26 dB at 1 kHz and 21 dB at 15 kHz, are respectable for a moving-magnet of the period, though not spectacular by the standards of the best CD-4 cartridges.
Collectibility and Market
The AT-15 turns up on the secondary market mostly as a variant badge rather than a clean model name, so pricing moves around. Recent eBay listings include an "Audio Technica AT-15Sa Vintage cartridge/stylus" at $160, two AT-15Ea MM cartridges at $120 and $140, and a new-old-stock ATN15XE stylus tip at $230. On the Russian market, a Maketto/Yahoo Auctions listing for an AT-15Ea/G showed a current bid of 4,488 ₽ / 6,800 ¥ at the time it was observed, and a VK listing described a used AT-15EA/G as complete with original box, cup, documents, and the original ATN-15Ea stylus. Hifishark maintains a model page for the AT-15 Ea aggregated across more than 400 marketplaces, so the cartridge still circulates in collector channels.
Replacement styli are the practical concern. DaCapo Audio offers a nude elliptical ATN-15 stylus that fits the AT-15 E/Ea/XE and also serves as an economical replacement option for the Shibata versions. An ATN20 HE hyperelliptical stylus is listed as compatible with the AT15 and AT15SA among others. Beyond stylus replacement, no common failure modes or maintenance procedures specific to the AT-15 surfaced in the available record. The usual caveats about aging cantilever suspensions apply, but they aren't documented for this model.
The AT-15 is a working CD-4 cartridge with documented period test results, a Shibata or elliptical stylus depending on variant, and a paper trail from two credible magazines. It has no clear family tree. The relationship between the E, Ea, XE, G, S, and Sa designations is not documented anywhere the Archive has found, so confirm the actual stylus profile before assuming Shibata.
eBay Listings
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