by Julian Hirsch, Hirsch-Houck Laboratories
FEATURES
Moving-magnet construction with samarium-cobalt magnet (for low mass) and symmetrical coils (for greater separation)
User-replaceable stylus assembly
Tubular aluminum cantilever coated with sapphire for stiffness and low moving moss
Cantilever electrically grounded through its stabilizing tie wire to drain off electrostatic charges
Stereohedron II line-contact stylus
Recommended tracking force: 0.75 to 1.5 grams
Weight: HZ9S, 4 grams; LZ9S, 3.8 grams
Recommended load impedance: HZ9S, 47,000 ohms, 275 picofarads; LZ9S, greater than 100 ohms, capacitance not critical
THE Epoch II series of moving-magnet phono cartridges from Stanton Magnetics combines several new design concepts with styling strikingly different from the company's previous cartridges. The Epoch II cartridges have low-mass bodies that are ideally suited to today's light tone arms.
Two versions of the cartridge body are available: a conventional "high-impedance" model, designed to drive the 47,000-ohm moving-magnet phono input of a preamplifier, integrated amplifier, or receiver, and a "low-impedance" version suitable for use with a typical moving-coil-cartridge input termination of 100 ohms or more. In combination with three different replaceable (and interchangeable) stylus assemblies, these options provide the Epoch II line with six models in all, covering a broad price range and suitable for use with a variety of music systems. This mix-and-match approach also makes it possible to upgrade any of the lower-priced models simply by installing the appropriate replacement stylus.
The stylus used in the higher-priced Epoch II cartridges is a diamond with an improved Stereohedron II extended-line-contact shape. Its radii are 0.2 and 3 mils, and it is said to touch the groove wall over 80 percent of the groove's nominal depth. One of the lower-priced cartridges uses a Stereohedron I tip with 0.3- and 2.8-mils radii, and the least-expensive Epoch II model is fitted with a 0.2 x 0.7-mil elliptical stylus.
Earlier Stanton cartridges have also offered low-impedance, low-output coils that make them "moving-coil equivalents." As the manufacturer points out, this approach provides the acknowledged advantages of a moving-coil design (principally its independence of loading interactions and extended high-frequency response thanks to the elimination of the low-pass filter formed by the coil inductance and load capacitance) without the drawbacks of a moving-coil's typical fragility and (usually) non-replaceable stylus.
Since the Epoch II LZ models have the low output voltage of a typical moving-coil cartridge, they are completely compatible with any MC preamplifier input or can be used with a head amplifier or trans former.
For this report, we tested the top-of-the-line Epoch II cartridge, the HZ9S, and we also made limited tests of the LZ9S low-impedance model, which uses the same stylus as the HZ9S. Each of these cartridges is priced at $250, with re placement styli available for $90.
The least-expensive Epoch II cartridge, the HZ6E, is only $95, and its stylus is priced at $40. Stanton Magnetics, Dept. SR, Terminal Dr., Plainview, N.Y. 11803.
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HIRSCH-HOUCK LAB MEASUREMENTS
Frequency response (with CBS STR 100 test record): HZ9S, 40 to 20,000 Hz +0.5,-3 dB referred to 1,000-Hz level; LZ9S, +0.5,-2 dB
Channel separation: HZ9S, 22 dB at 1,000 Hz, 24 dB at 10,000 Hz; LZ9S, 20 dB at 1,000 Hz, 23 dB of 10,000 Hz
Output voltage la: 3.54-cm/s groove velocity, 1,000 Hz): HZ9S, 3.4 millivolts; LZ9S, 0.1.5 mV
Channel imbalance: HZ9S, 0.6 dB; LZ9S, 1.28 dB
Vertical stylus angle: 22 degrees (both models)
Optimum load: HZ9S, 47,000 ohms in parallel with 360 picofarads; LZ9S, greater than 100 ohms, capacitance not critical
Tracking ability (at 300 Hz with German HiFi *2 test disc): 80 micrometers at 0.75 gram, 100 gm at 1 gram
IM distortion: less than 3% with groove velocity between 7 and 22.5 cm/s; 5% at 27 cm/s Tone-burst distortion: less than 1% with groove velocity between 15 and 30 cm/s
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Lab Tests
The two cartridge bodies were in stalled in plug-in shells for a low-mass tone arm that is compatible with the low mass of the Epoch II cartridges. The compliant styli resonated at 7 to 8 Hz in this arm, which caused no problems in tracking warped records, but it is obvious that for best results the Epoch II series cartridges should not be in stalled in massive tonearms.
We made complete tests of the HZ9S, and we measured the output, frequency response, and channel separation of the LZ9S by installing the stylus from the HZ9S in the other body. This approach allowed us to assess differences resulting from the LZ's low coil impedance with out having to allow for the effects of normal stylus variations. For both measurements and listening tests with the low-impedance body, we used a high-quality MC transformer whose response is very flat and extends well beyond the range of the cartridge and test records.
We used a 1-gram force for most of our tests, and frequency-response measurements with different load capacitances showed that this was not a critical factor, although higher values made a slight improvement. We used 360 picofarads.
The frequency response of the HZ9S with the CBS STR 100 test record had a slight, well-damped peak at 10,000 Hz, dropping off slightly at higher frequencies. It varied over a ± 2-dB range from 40 to 20,000 Hz. The two channels had virtually identical response and channel-separation characteristics.
Substituting the LZ9S body, we found a similar response up to 10,000 Hz and beyond, but the output remained stronger above that frequency and did not appear to be rolling off above our 20,000-Hz measurement limit.
The tracking ability of both models was outstanding. At 0.75 gram they tracked the 30-cm/s tones of the Fairchild 101 test record, the high-level 32-Hz tones of the Cook 60 record, and the 80-micrometer level of the German HiFi #2 record.
At 1 gram, the last disc could be tracked without difficulty at its maximum level of 100 micrometers, an impressive achievement for any cartridge. The only time a higher force was needed was in the musical tracking tests of the Telarc "Omnidisc" record; at their higher levels, the cannon shots in the 1812 Overture required a force of about 1.25 grams to keep the stylus in the groove. Anyone who is familiar with the "Omnidisc" album will appreciate the unusually good tracking ability shown by the Epoch II cartridges.
Conventional tracking-distortion measurements revealed little about the cartridge (this is becoming a common problem, since the test records we normally use no longer tax the tracking abilities of the best of today's cartridges). The response to the 1,000-Hz square-wave bands on the CBS STR 112 test record showed a single low-level and well-damped overshoot cycle corresponding to the 10,000-Hz response peak but was otherwise about as good a square wave as we have seen from this disc. The LZ9S's square-wave response was so close to that of the HZ9S that we would consider them essentially equivalent in this as well as all other substantive respects.
Comments
We played the Epoch II cartridges in our regular music system, using the MC transformer when the LZ9S was installed. The two cartridges both sounded excellent and, as far as we could tell, the same. This is hardly surprising, since the only measurable difference in their frequency responses was above 15,000 Hz. In any event, we cannot attribute any special sonic quality to either version, since they sound about as neutral as any cartridge we know of. And that is how a cartridge should sound!
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Also see: Tonearms (Jan. 1985)
Source: Stereo Review (USA magazine)