ADC's Jewel of a Pickup
ADC Astrion fixed-coil phono pickup with elliptical diamond stylus (tip radii, approx. 6 3/8 by 37 1/2 micrometers). Price: $235; RSA replacement stylus, $99. Warranty: "limited," one year parts and labor, excluding stylus wear. Manufacturer: Audio Dynamics Corp., Pickett District Rd., New Milford, Conn. 06776, USA.
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FREQUENCY RESPONSE & CHANNEL SEPARATION (test record: STR-170)
Astrion
Frequency response
L-ch
R-ch
Channel separation
-1.5 dB, 20 Hz to 20 kHz
-1 1/2 dB, 20 Hz to 20 kHz
>=25 dB, 360 Hz to 8 kHz;
>15 dB, 31 Hz to 20 kHz
SENSITIVITY (at 1 kHz) 0.95 mV/cm/ sec.
CHANNEL BALANCE (at 1 kHz) +-0 dB
VERTICAL TRACKING ANGLE = 30°
LOW-FREQUENCY RESONANCE (in SME 3009)
vertical 7.5 Hz; 11 dB rise
lateral 8 3Hz, 11.25 dB rise
MAXIMUM TRACKING LEVEL (re RIAA 0 VU; 1.2 grams) at 300 Hz + 12 dB
WEIGHT 5.7 grams
SQUARE-WAVE RESPONSE (1 kHz)
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AFTER YEARS OF steady but gradual improvement, the fixed-coil cartridge field seems subject to radical change in the Eighties, and ADC is a top-drawer example of both trends, past and present. The last ADC pickup we reviewed-the Integra XLM-III (September 1980), with its integral carbon-fiber headshell allowing adjustments for overhang and vertical tracking angle-prompted us to wonder aloud "why nobody has made cartridges that way before." ADC's latest, the Astrion, enjoys top-of-the-line status and, though different in format from the Integra, is no less interesting in design and materials.
Completely hand-assembled, with individual inspection of every internal component, the Astrion aims at a discriminating audience, indeed. In place of aluminum or one of the more exotic alloys, the cantilever shaft is formed of a single sapphire crystal. Sapphire's high stiffness-to-mass ratio and strength make it superior to other cantilever materials, according to ADC. The company de scribes the diamond tip as elliptical, though the hand-polished narrow-radius surfaces that contact the groove walls are said to present an extended bearing area comparable to that of the Shibata and other multi-radial styli. The tip is also claimed the smallest ever made by ADC, which adds that a redesigned suspension system--without wires, adhesives, or governors--keeps moving mass low and compliance high.
On the test bench at Diversified Science Laboratories, the Astrion demonstrated clearly the benefits of its careful design and construction. With vertical tracking force set at 1.2 grams, the mean of ADC's recommended range, sensitivity came in at a healthy 0.95 millivolt. Tracking ability was excellent in the 300 Hz test, and separation--well in excess of 25 dB over much of the midrange-is more than adequate.
Vertical tracking angle, when measured as a function of second-order inter modulation distortion on the low-frequency bands of a special DIN test record, was approximately 30 degrees, the highest band on the test record but consistent with the VTAs of many other top-notch pickups measured for us in the past. The high-frequency IM bands on the same test disc, however, documented a VTA of 22 degrees; this figure presumably reflects stylus rake angle. (See "A New Angle in Record Playing," March.) Frequency response of the Astrion, measured with the CBS test disc, is ruler flat from 20 Hz to 3.5 kHz, followed by a broad and very shallow dip in the upper treble. In our "standard" medium-mass SME arm, its vertical resonance falls a bit on the low side, indicating the desirability of somewhat lower arm mass.
Resonance amplitudes are consistent with those of other cartridges measured by DSL, though the numbers are larger than our former (CBS) technique delivered.
Comments from auditioners on the sonic character of the Astrion are a litany of superlatives, with many of the compliments centered on its high-frequency performance. Though detailed and precise, high strings, brass, and the like emerged free of the etched, steely quality that can make long-term listening less than pleasant. All auditioners were unanimous in assessing this model as a remarkably uncolored transducer, but some commented specifically on its "sweetness" and "airiness." It also possesses a remarkable ability to discriminate among instruments in complex orchestral pieces, and one listener noted that it makes surface noise far less prominent than usual.
It's not often that we can pronounce a cartridge to be as deserving of top-of-the-line billing as this one is. Considered in light of its fine craftsmanship, rare materials, and-most important-sonic character, the Astrion is nothing less than a jewel of a pickup.
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(High Fidelity, Jul. 1981)
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