by B. V. Pisha
IN OCTOBER 1970, the world was first introduced to a new phenomenon in the audio industry--CD-4--as presented by the Victor Company of Japan (NC) at the fall meeting of the Audio Engineering Society in New York. This development, together with the CBS/Sony SQ and Sansui QS matrix systems, constituted a revolution not unlike that which occurred in 1958 when the stereo record was introduced.
The advent of compatible, discrete, four-channel, CD-4 recordings, with their FM-modulated 30-kHz carrier, brought about the need to develop a cartridge that would have a wide frequency response-beyond 30 kHz and preferably to 50 kHz--so as to properly reproduce the new CD-4 records that have almost three times the frequency range of conventional records. To accomplish this, the new cartridge had to have a lower mechanical impedance (mass) of the vibrating system and an elevated high-end resonant frequency. The new stylus tip, as developed by Shibata in Japan, was designed to meet these requirements by enlarging the contact area of the stylus. The Shibata stylus has nearly the same tip radius as the elliptical stylus but, also, four times as much contact area with the record groove. Proper reproduction of the recorded signal in the 30 50 kHz region requires intimate stylus-to-groove contact. In order to seat the Shibata tip firmly into the record groove, an increased tracking force of two grams is required. However, because of its increased contact area, the two-gram tracking force of the Shibata tip can be expected to decrease by about four times both record and stylus wear, as compared to a conventional elliptical tip tracking at 1.5 grams.
In June 1971, NC marketed in Japan a CD-4 demodulator and the first CD-4 cartridge with the Shibata stylus, identified as the 4MD-1X. This cartridge was never sold in this country, but is still available in Japan. To indicate the progress that has been made in the design of CD-4 cartridges, the early Victor 4MD-1X (manufactured by Victor) is profiled along with the other cartridges. The current JVC cartridge sold in this country is the 4MD-20X, manufactured by Audio-technica and similar to the AT-14S.
With RCA announcing that they were going to produce the CD-4 records, it did not take long for the industry to introduce the new-type cartridge. Currently, the influx of cartridges capable of reproducing the CD-4 records is increasing dramatically. It seems that every few weeks another cartridge manufacturer is announcing his intention to market the new type cartridge. To date, only a few of the cartridges are available on the market. Most of these cartridges use the Shibata tip (Victor, Audio-technica, Technics, Ortofon, and Grace) either as a nude diamond or the diamond tip fused to a metal shank; Pickering/Stanton are using their Quadrahedral tip which is designed to cover the same contact area and is somewhat similar to the Shibata tip; whereas Grado Laboratories is continuing to use the conical tip, but with a low tip mass that obviates the need of a Shibata-type stylus to track CD-4 records. This, also, is the only standard cartridge with a very low inductance so that a lead as long as 20 feet may be used without a detrimental effect on the 30-kHz carrier signal.
As noted earlier, CD-4 cartridges are coming from many manufacturers and sometimes from unexpected sources. For example, AKG, well-known for their microphones and headphones, has been reported to be preparing to market a CD-4 type cartridge in three models, with the top cartridge to be designated the PU4E. The Diamond Stylus Co. of London also announced their forthcoming entry into the field with the MG 14E and MD 14D cartridges. (Additional CD-4 capable cartridges will be profiled later this year.-Ed.)
-------- Discrete four-channel record groove as seen with 'the scanning
electron beam microscope (original magnification 1 500x). Each wall
of the groove carries two sets of signals: the sum of the front and
rear signals on the stereo base band and the difference of the front and
rear signals on the carrier band. -Courtesy RCA Records.
Equipment
To perform a reasonably accurate evaluation of the CD-4 cartridges, the playback equipment was chosen with great care. After trying a few direct-drive turntables, the Technics by Panasonic Model SP-10 and base was chosen because of its consistency and ability to preset the 33 1/3- and 45-rpm speeds by individual speed controls. It is most important, when using test records at both 33 1/3 and 45 rpm, that the speed regulation remain constant as the speed rate is shifted from one to the other. Vertical rumble for the SP-10 is specified at less than -65 dB (DIN A) and less than -70 dB (DIN B), while wow and flutter of less than 0.03% wrms is claimed.
A number of tone arms were examined and the Audio-Technica AT-1009 was installed on the Technics turntable. The AT-1009 tone arm was specifically designed for use with CD-4 cartridges. The arm is lifted and lowered by a pneumatic control. One advantage of the AT-1009 tone arm is that the antiskating can be varied in the dynamic state when checking this parameter. It is essential that the anti-skating pressure be adjusted as accurately as possible for all CD-4 cartridges so that the front and rear right channels reproduce properly with a minimum of mistracking distortion. Our experience indicates that this is of primary importance, especially when lower-priced cartridges are installed in a tone arm or cartridges having other than the Shibata or Shibata-like configuration are used. The Audio-technica AT-1009 cable capacitance between the cartridge connectors and the phono plugs is 77 pF for the right and 78 pF for the left side.
The Shure Brothers C/PEK-3 Stereo Cartridge Analyzer with its accompanying test records (TTR-107 and TTR-103) was acquired and modified so that it could be used to evaluate the CD-4 cartridges with their 50-kHz bandwidth. The modified version of the C/PEK-3 will be available shortly from Shure Brothers. The C/PEK-3 was used to check channel orientation, crosstalk, balance tests, phase relationship, and antiskating and tracking force optimization. The monitor outputs on the C/PEK-3 with their 700-ohm output impedance appeared to introduce no recognizable errors, so the sweep-frequency response, IM distortion, and square-wave measurements were made from this point.
The sweep-frequency is plotted automatically on the Justi-Meter III, the graphic audio recorder designed and developed by the former editor and publisher of AUDIO, C. G. McProud, and marketed by Audio-Technica U.S., Inc. The sweep source for this unit is supplied by the Bruel & Kjaer frequency-sweep record, QR-2009, with a range from 20 to 20,000 Hz. The high frequency-sweep range from 1000 to 50,000 Hz is supplied by the JVC test record, TRS-1005. The time of the sweep in the TRS-1005 is such that it matches the B&K QR-2009, assuming that the 1000-Hz reference tone is started at the 50 Hz mark on the chart. The actual high frequency-sweep starts at the 100 Hz line on the chart so that the recorded plot is just ten times the indicated frequency on the chart. We found the Justi-Meter III to be more than adequate for measuring cartridge performance. Its response closely matches a point-to-point response plotted for one cartridge. It is also quite useful for recording sweep-frequency response of amplifiers, filters and experimental units.
The measuring preamplifier has two positions--FLAT and BASS BOOST. The bass-boost position is equalized to provide a boost of 6 dB/octave below 500 Hz, and to be flat above that turnover frequency. IM measurements are made through the preamplifier which is set for BASS BOOST. The square-wave photographs are also made through the preamplifier when it is set to the FLAT position. The measuring preamplifier with its gain of 40 dB was described by C. G. McProud in AUDIO, June 1972.
To prevent the attenuation of the 30-kHz carriers, it is imperative that the cable capacitance between the cartridge and the input to the demodulator not exceed 100 pF total, which includes the wiring in the tone arm. This requirement places a burden on the salesman who is demonstrating a turntable that is quite a distance from the demodulator, as is the case in most every audio demonstration room. To overcome this problem, there is available from M&W Radio Corp., Williston Park, N.Y. 11596, a very small stereo booster amplifier voltage follower to which the turntable is connected by an audio cable not exceeding 100 pF per stereo side from the cartridge to the preamplifier. This unit properly loads the CD-4 cartridge. Subsequently, a length of audio cable not exceeding 8200 pF per stereo side may be connected between the output of the booster amplifier and the input to the demodulator. Up to 546 feet of low-capacitance cable (15 pF/ft) may be used without causing a significant response change or a phase rotation up to 50 kHz. The ideal location for this unit is inside the turntable base or separately close-by, thus eliminating the necessity of low capacity cable. The unit has been tested and approved by JVC for use in conjunction with CD-4 demodulators. We have tested all the cartridges in this evaluation with this booster amplifier, and all results were identical with the original results.
A Polaroid 350 camera is used to make all the square-wave photographs. The camera is fitted with a portrait lens adapter, as is the view finder, and a cable release. The camera is mounted on a rigid tripod and placed 19-20 inches from the oscilloscope. The intensity of the oscilloscope trace is reduced to a barely visible state after focusing the camera. With the black and white Polaroid film (speed 3000), the exposure time is three seconds. The exposures are made in a totally dark room to eliminate the light reflections from the face of the oscilloscope and to defeat the photocell shutter-control mechanism of the camera.
The remaining test equipment consisted of an IM distortion analyzer; an audio VTVM that can measure down to one millivolt, full scale; a resistance, capacitance, and inductance bridge; oscilloscopes, low-capacitance connecting cables made up from any of the following: Alpha 2312 (15 pF/ft), Columbia 01395 (11 pF/ft), or Dabum 2693 (11 pF/ft), and the following test records: B&K QR-2009, JVC TRS-1005, Columbia STR-111, Columbia STR-100, Shure Brothers TTR-107 and TTR-103, DIN 2, and Grado Laboratories RL-1758. We tested only one cartridge per day, thus providing a 24-hour recovery period for the groove walls of the test records as well as the CD-4 music test (listening) records.
To eliminate the power line variations, an autotransformer followed by a Variac is employed and the line voltage constantly monitored for a reading of 117 volts. The room temperature for all cartridge tests was maintained at 69° F± 1° and the relative humidity was 33%± 3%.
Procedures
The cartridge to be tested is weighed on a gram balance beam scale and the weight recorded. This is followed by the measurements of the d.c. resistance and the inductance. The stylus is then examined under the microscope at 200x to ascertain that it is clean and properly mounted.
Following these procedures, the cartridge is mounted onto the Audio-technica AT-1009 tone arm cartridge shell and adjusted for a 15 mm overhang. At this point the arm is balanced so that the stylus is about 1/8 in. above a blank acetate disc and the stylus tracking pressure is then set using a Shure SFG-2 precision stylus force gauge. It is generally accepted that the ideal stylus pressure for the Shibata stylus (or its equivalent) is two grams when playing CD-4 discs. However, because there may be some CD-4 cartridges in the near future that should not be used at a two-gram stylus pressure, the arbitrary stylus pressure of 1.75 grams is used for all the evaluations. Therefore, the optimum stylus pressure was not determined for any cartridge. However, the Grado FTR + 1 was also evaluated at 1.25 grams stylus pressure. It was also noted that at the 1.75 gram stylus pressure all cartridges and the AT-1009 tone arm were able to track the worst warped records in our collection, including a washboard type warp, without noticeable distortion. Prior to actual use of the cartridge, the stylus is again cleaned. It takes only a little dust on the stylus or the CD-4 disc to cause mistracking with subsequent deterioration in the rear channel signal.
To measure the channel orientation, crosstalk, and balance tests, the cartridge is connected to the Shure Brothers C/PEK-3 Stereo Cartridge Analyzer, using the TTR-107 test record. A phase check is then performed using the TTR-103 test record. This is an important test inasmuch as improper phasing of the cartridge and the rest of the connections employed in the CD-4 system will prevent a null point when adjusting the separation controls on the demodulator. The final testing of the cartridge with the C/PEK-3 analyzer is adjusting the antiskating device and performing the trackability tests, using the TTR-103 test record. There are three sections to the trackability test: high frequency, mid-frequency, and low frequency. The high-frequency tracking test is a 10.8 kHz pulse; the mid-frequency tracking test is a 1000 + 1500 Hz lateral-cut tone; and the low frequency tracking test is a 400 + 4000 Hz lateral-cut tone. The low- and high-frequency tests have four velocities: 15, 19, 24, and 30 cm/sec. The mid-frequency test has four velocities: 20, 25, 31.5, and 40 cm /sec. The TTR-103 test record, in conjunction with the C/PEK-3 cartridge analyzer, is the best available means to determine the trackability of a cartridge, and the oscilloscope displays leave little or no doubt about its performance. This test is usually augmented by listening concomitantly to the reproduced sound via speakers. However, in most instances you can hear the buzzing the cartridge makes when it no longer can track a given band as well as see the distorted display on the oscilloscope. We must point out, however, that the majority of recorded music on discs generally has a velocity below 15 cm/sec and only occasionally does it reach 25 to 30 cm/sec.
Although the C/PEK-3 does measure cartridge output in millivolts, we measured the voltage output of each cartridge, correctly terminated, with the STR-100 test record and an audio VTVM capable of measuring microvolts. The signal output of the cartridge is measured at a signal of 3.54 cm/sec at 1000 Hz. This figure is divided by 3.54 to obtain a relative output in mV for a stylus velocity of 1 cm/sec, thus providing a comparative figure.
(Although all our Columbia and RCA test records were lost sometime ago, most of them have been replaced by the ever present generosity of W. Rex Isom [RCA] and Benjamin B. Bauer [ Columbia] to whom we owe a debt of gratitude. We also wish to thank Ben Bauer for loaning us his copy of the CBS STR-111 test record so that we could examine the IM distortion and square waves of the cartridges. We regret that Columbia is not considering a new cutting of the out-of-stock but very important STR-111 test record, since it is the standard of the industry for IM distortion and square waves.) IM distortion measurements are made using the STR-111 test record with the cartridge connected to the C/PEK-3 and the monitor output of the C/PEK-3 connected to the measuring preamplifier set to BASS BOOST. The output of the measuring preamplifier is connected to the IM distortion analyzer.
Although IM distortion measurements are made on all bands of the STR-111, we follow the C. G. McProud reporting method and report only the +9 dB lateral modulation at 200 and 4000 Hz and the +6 dB vertical modulation at 200 and 4000 Hz. The resulting figures are only relative rather than absolute.
Continuing to use the STR-111, the square-wave photos are made, using the FLAT position on the measuring preamplifier.
For the frequency-response measurements, the monitor output of the C/PEK-3 is connected to the cartridge input of the Justi-Meter III graphic audio recorder. The B&K QR-2009 sweep record is used to record the sweep and separation from 20 to 20,000 Hz. The sweep from 1000 to 50,000 Hz is obtained from the JVC TRS-1005 sweep record. Recordings are made from both channels, but only the left channel is reported.
In all of the above test procedures, the total capacitance of the tone arm cable plus the interconnecting cables did not exceed 100 pF per channel.
When examining and comparing the data on the cartridges, it must be borne in mind that the data represents only the specific cartridges examined and can vary from cartridge to cartridge within any production run as well as from one production run to another.
CD-4 Cartridges and Demodulators
There are, at present, four separate demodulators, JVC 4DD-5, Lafayette 99H03345W, Panasonic SE-405H, and Pioneer QD-240, plus many receivers using the JVC system, under license. The Panasonic SE-405H is a unique demodulator in that it comes with a special semi-conductor-type cartridge, EPC-450C, that requires a 4-volt d.c. bias, which is available from the demodulator. This cartridge will be reported on in a future issue of AUDIO. A switch at the rear of the demodulator changes the cartridge input circuit to accept a moving-magnet cartridge or the Ortofon transformer for the SL 15Q. The Panasonic demodulator is also unique in that the 30-kHz carrier level can be set for each channel simply by using the outer grooves of a Quadradisc and adjusting the carrier level until the 4 cx RADAR indicator just lights up. The JVC system requires that a 400-Hz distorted signal, supplied by the CD-4 adjustment record (not a test record), be converted to as pure a tone as possible (as heard and/or seen on the oscilloscope) by use of the 30-kHz carrier control. Separation adjustments are made in the same manner for all demodulators. Should it be impossible to obtain a null point when adjusting the separation control for one channel, reverse the cartridge connections for that channel and repeat the separation adjustment until a null point is reached. The inability to obtain a null point is usually caused by incorrect connections at the cartridge (one side being out of phase).
As a part of the cartridge evaluation, each cartridge is connected to the Panasonic SE-405H and JVC 4DD-5 demodulators, respectively, and adjusted using the following adjustment records: General, JVC 4DE-205 (45 rpm); for rechecking the separation setting, the 33 1/3 JVC 4D-101, band 1; for rechecking the amplifier controls for equal volume (0 dB), the WEA PR 186; and for a final check of the separation, the 33 1/3 JVC RG 1281, band 1. Normally, the 45-rpm JVC adjustment record, 4DE-205, is sufficient for all adjustments, including the 30-kHz carrier level for the JVC 4DD-5 and Pioneer QD-240 demodulator. The Pioneer and Lafayette demodulators have not been used in any of our evaluations, as yet.
Listening Evaluation
The listening evaluation is made using a variety of records representing the gamut of CD-4 recorded music. Therefore, each cartridge underwent a rigorous listening evaluation with the following experimental and commercially available records:
1. Harman/Kardon CD-4 Calibration and Demonstration Quadradisc-DPD 1-0062
2. Mancini Salutes Sousa-RCA Quadradise, APD 1-0013
3. Carly Simon-No Secrets-Elektra Quadradisc, EQ-5049
4. Carolyn Hester-RCA Quadradisc, APD1-0086
5. RCA Quadradisc Highlights, DJD 1-0072
6. Dolly Parton-Bubbling Over-RCA Quadradisc, APD1-0286
7. Mandolin Serenade-JVC CD-4 Quadradisc, CD4W-7016
8. Artur Rubenstein--Rachmaninoff Piano Concerto No. 2RCA Quadradisc, ARD 1-0031
9. Debussy-La Mer--RCA Quadradisc, ARD1-0029
10. Virgil Fox--Heavy Organ at Carnegie Hall-RCA Quadradisc, ARD1-0081
11. Webersinke--Famous Organ Works by J. S. Bach-JVC, CD4K-7507E
12. Walter Carlos--Switched on Bach-CD-4 Experimental Record
13. Walter Carlos--Clockwork Orange-CD-4 Experimental Record
14. Difficult Passages--CD-4 Experimental Record
The speakers used in the listening evaluation are the Cerwin-Vega 211-R's in front and the AR-2a's in the rear. The last five records were used again when the speaker placement was reversed, the Cerwin-Vega 211-R's in the rear and the AR-2a's in front. It is realized that these speakers are disparate in their characteristics, especially in terms of efficiency. Because of these characteristics, the speaker placement was also used in the reverse. This is especially important when the sound emanating from the rear speakers is primarily ambience. The Integral System preamplifiers, Model 10, and amplifiers, Model 200 (100 watts per channel), were used to drive the speakers.
The last five records gave each cartridge a workout. In particular, the CD-4 experimental records, Switched on Bach and Clockwork Orange, are superb for checking CD-4 cartridges. Both of these records separated the excellent cartridge from the good cartridge with no uncertainty because of the highly explosive transients common to the Moog synthesizer.
In most instances, the listening evaluation agreed with the measurement tests. However, the listening evaluation should be the final criteria by which a cartridge is judged. We believe in the axiom put forth many years ago by the late C. J. LeBel". If it measures good and sounds bad, it is bad."
Conclusions
All the CD-4 cartridges evaluated reproduced the CD-4 recordings well and the resultant sound was pleasant to the ear in the listening evaluation. Three cartridges stand apart from the rest to this listener-Audio-technica AT20SL, Ortofon SL15Q, and Audio-technica AT15S. The AT20SL and SL15Q are considered to be equal in our listening evaluation with the AT15S a close second. These three cartridges appear to have a better definition of individual instruments, especially of the percussive nature. The Audio-technica AT20SL and the Ortofon SL15Q reproduced the last five records, and especially the last three, smoothly, with a very clean sound.
In a letter written to AUDIO (November 1973), Mr. James H. Kogen, vice president, Shure Brothers, Inc., made a point that is well-taken-that a separate cartridge should be used for stereo reproduction and another for CD-4 reproduction. In general, we agree with Mr. Kogen. However, we take a small exception and feel from our own listening that the very top CD-4 cartridges can play both without a trade-off.
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Audio-technica AT20SL
Audio-technica cartridges use two independent permanent magnets mounted at 45-degree angles, perpendicular to the two sides of the record groove. Each magnet is an electrical generator reproducing only the signal from one side of the record groove, thus maximizing separation. This model is identical to the AT15S, except that the AT20SL is hand-selected for all parameters, including flattest possible response to 50 kHz.
Frequency response is flat from 50 Hz to 8 kHz ± 2 dB, + 3 dB at 10 kHz, and +4 dB at 20 kHz. The double peaks at about 23 and 26 kHz are +5 dB, then the response drops to +1 dB at 40 kHz. Separation averages 20 dB from 100 Hz to 5 kHz, down to 15 dB at 10 kHz and 16 dB at 20 kHz. Trackability is one of the best we have ever seen. The AT20SL is one of the two top CD-4 cartridges reported here. Its sonic clarity is superb, one of the smoothest we have ever encountered. Transient response is excellent. One does not realize all the sounds present on a CD-4 recording of the Moog synthesizer, as well as both electronic and pipe organs, until played with a top-of-the-art cartridge.
Wt. 9.03 g; d.c. res. 550 ohms; Ind. 378 mH; Output 0.65 mV/1-cm/sec; IM dist. 2.5% lat., 3.4% vert.; Crosstalk-22 dB; Ch. Bal. 0 dB; Trackability: High freq. (10.8 kHz pulsed) 30 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) 31.5 cm/sec; Low freq. (400 + 4000 Hz lat. cut) 30 cm/sec. The stylus is a nude diamond with the Shibata configuration. $150.00.
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Audio-technica AT15S
Construction is identical to the AT20SL, since the top of the line cartridge is hand-picked from the production run of the AT 15S. Frequency response is flat from 50 Hz to 8 kHz ± 2 dB, + 2 dB at about 15 kHz, + 1 dB at 20 kHz, + 1 dB at 30 kHz,-2 dB at 40 kHz, and-5 dB at 50 kHz. Separation averages 20 dB from 50 Hz to 10 kHz, down to 16 dB at 12 kHz and 12 dB at 20 kHz. Musically, the AT 15S is not quite as good as the AT20SL. Transient response is excellent, as is the bass response. Sonic clarity is excellent, particularly in electronic synthesizers, electronic and pipe organ, and piano. Overall, it produces crisp, clean sound.
Wt. 8.52 g; d.c. res. 445 ohms; Ind. 408 mH; Output 0.83 mV/1-cm/sec; IM dist.: 2.6% lat., 2.4% vert.; Crosstalk-24 dB; Ch. Bal. 0.5 dB; Trackability: High freq. (10.8 kHz pulsed)
30 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) 25 cm/sec; Low freq. (400 + 4000 Hz lat. cut) 19 cm/sec. The stylus is a nude diamond with the Shibata configuration. $100.00.
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Audio-technica AT14S
The AT 14S is next to the lowest priced CD-4 cartridge with a Shibata stylus in this line. The response curve is one of the flattest we have encountered, ± 2 dB from 30 Hz to about 45 kHz, and down-3 dB at 50 kHz. Separation is about 20 dB throughout the spectrum up to about 17 kHz and then decreases to 9 dB at 20 kHz. Although the sound is crisp, it has a tendency towards stridency at the high frequencies and the bass has a slight tendency towards being boomy, especially low bass. There is some distortion present in the loud bass passages in the rear channels as well as in some difficult music passages.
This cartridge and the JVC 4MD-20X are reported to be identical-both are made by Audio-technica.
Wt. 6.5 g; d.c. res. 446 ohms; Ind. 383 mH; Output 0.69 mV/ 1-cm/sec; IM dist.: 2.4% lat., 1.7% vert.; Crosstalk-30 dB; Ch. Bal. 0.5 dB; Trackability: High freq. (10.8 kHz pulsed) 24 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) 31.5 cm/sec; Low freq. (400 + 4000 Hz lat. cut) 24 cm/sec. The stylus is a nude diamond with the Shibata configuration. $75.00.
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Grace F8/F
The Grace cartridge is manufactured by the Shinagawa Musen Co., Ltd., in Japan. We have not seen many examples in the West, though Sumiko, P.O. Box 5046, Berkeley, Calif. 94705, has started importing two Grace cartridges, this model and the F8/L. The response curve is ± 3 dB from 20 Hz to about 10 kHz, dropping to-4 dB at 10 kHz, then slowly rising to-2 dB at 30 kHz, and down-6 dB at 50 kHz. Separation is about 19 dB throughout the spectrum to 20 kHz. Musically, the high frequencies appear to be a bit strident. Some tracking difficulties and distortion were encountered in loud mid-frequencies and bass. The overall sound was a little hard.
Wt. 6.5 g; d.c. res. 472 ohms; Ind. 359 mH; Output 0.58 mV/1-cm/sec; IM dist.: 0.8% lat., 2.3% vert.; Crosstalk-27 dB; Ch. Bal. 0 dB; Trackability: High freq. (10.8 kHz pulsed) 24 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) less than 20 cm/sec; Low freq. (400 + 4000 Hz lat. cut) less than 15 cm/sec. The stylus is a nude diamond with the Shibata configuration. $109.95.
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Grado Laboratories FTR+1
This is the sleeper among the CD-4 cartridges. The stylus is a spherical diamond (0.5 mil) with a tip mass so low that it doesn't require special facets to track CD-4 records. And the price quoted is $11.95. Although we used a stylus tracking force of 1.75 g for all the cartridges, we made an exception for the FTR + 1 and also measured it at a tracking force of 1.25 g, as suggested by Grado Laboratories. The cartridge is a type of variable reluctance, not too different from the old General Electric variable reluctance cartridge. Because of its low inductance, up to 20 feet of cable may be used without any effect upon the very high frequencies. The frequency response curves were reasonably identical from 20 Hz to 20 kHz at both 1.75 and 1.25 g tracking force. At 1.25 g the response is ± 2 dB from 20 Hz to 8 kHz, rising to + 9 dB at about 13 kHz, + 1 dB at 20 kHz and about + 7 dB at about 26 kHz and then falling off rapidly, +1 dB at 30 kHz,-8 dB at 40 kHz, and-13 dB at 50 kHz. At the 1.75 g tracking force, there is a +2 dB peak at about 23 kHz and then rapidly falling off,-2 dB at 30 kHz,-8 dB at 40 kHz, and-13 dB at 50 kHz. It appears that the 1.25 g tracking force brought about another peak at about 26 kHz, whereas at the 1.75 g tracking force there is only a minor peak at about 23 kHz. Separation is about 21 dB from 50 Hz to 10 kHz, dropping to 17 dB at 15 kHz and 15 at 20 kHz. Musical response is relatively clean, but is not as crisp as with others. Transient response is good. It is a bit strident in the high end with some distortion at the very high end. This cartridge acquitted itself well with the bass organ pedals as well as the Moog synthesizer. Some distortion was noticed in the very loud musical passages.
This is an amazing cartridge when one considers its price. We would not hesitate to recommend it for medium-priced systems or OEM use.
Wt. 5.4 g; d.c. res. 710 ohms; Ind. 58.7 mH; Output 0.61 mV/1-cm/sec; IM dist. 2.3% lat., 2.7% vert. (3.2% vert. at 1.25 g.); Crosstalk-28 dB (-30 dB at 1.25 g.); Ch. Bal. 0.75 dB (0 dB at 1.25 g.); Trackability: High freq. (10.8 kHz pulsed) 24 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) 25 cm/sec (20 cm/sec at 1.25 g.); Low freq. (400 + 4000 lat. cut) 19 cm/sec (15 cm/sec at 1.25 g.). $11.95.
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Ortofon SL15Q
This is the only moving coil cartridge among the current CD-4 cartridges and requires a transformer to step up the voltage for the average preamplifier. Frequency response is ± 2 dB from 40 Hz to 13 kHz, +5' dB at 20 kHz, +8 dB at 40 kHz, and +2 dB at 50 kHz. Separation is generally about 17 dB across the spectrum to 9 kHz, dropping to 16 dB at 10 kHz, 15 dB at 15 kHz, and l l dB at 20 kHz. This cartridge is tied with the Audio-technica AT2OSL as one of the two top cartridges reported here. Like the AT2OSL, its sonic clarity is superb and it is one of the smoothest cartridges we have encountered. Transient response is excellent. All the sounds recorded by the Moog synthesizer are reproduced clearly as are the electronic and pipe organ sounds. This is a state-of-the-art cartridge. We might add that the transformer should be marked to identify the left and right channels. The white dot on the transformer is for the right cartridge lead and the white phono plug from the transformer goes to the right phono jack on the demodulator.
Wt. 7.6 g; d.c. res. 2.55 ohms; Ind. 112 micro H; Output with transformer 2.79 mV/1-cm/sec; IM dist. 1.5% lat., 2.0% vert.; Crosstalk-26 dB; Ch. Bal. 1.5 dB; Trackability: High freq. (10.8 kHz pulsed) 30 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) 25 cm/sec; Low freq. (400 + 4000 Hz Lat. cut) 19 cm/sec. The stylus appears to be a nude diamond with the Shibata configuration. $160.00 (estimated).
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Pickering UV-15/2400-Q
This Pickering cartridge is considered the first U.S.-made CD-4 cartridge. The response curve is quite flat, ± 3 dB from 20 Hz to over 20 kHz,-3 dB at 10 kHz, +2 dB at 20 kHz, +4 dB at 30 kHz, + 1.5 dB at 40 kHz, and-4 dB at 50 kHz.
The resonant peak is from about 21 kHz to 30 kHz. Separation averages 21 dB from 50 Hz to about 8 kHz, down to 17 dB at 10 kHz, and 11 dB at 20 kHz. This cartridge has the lowest IM distortion of the cartridges reported herein. If some parameters can be redesigned and the IM distortion remain as is, it would be a superior cartridge. Musically, the high frequencies sound a little strident, particularly on string instruments. Transient response is good. Slime tracking distortion was evident on loud organ bass passages. There was some distortion in the mid-frequencies. The overall sound is a little hard.
Wt. 5.66 g; d.c. res. 672 ohms; Ind. 297 mH; Output 0.58 mV/1-cm/sec; IM dist: 1.0% lat., 0.8% vert.; Crosstalk-25 dB; Ch. Bal. 0.75 dB; Trackability: High freq. (10.8 kHz pulsed) 24 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) less than 20 cm/sec; Low freq. (400 + 4000 Hz lat. cut) less than 15 cm/sec. The diamond stylus has a Quadrahedral configuration which is not unlike the Shibata configuration. Both the back and front end of the stylus appear to have identical facets. Evaluation of this cartridge was performed with the "Dustamatic" brush removed. $124.95.
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Stanton 780/4DQ
This cartridge is considered to be the second U.S.-made CD-4 cartridge. The response curve is ± 3 dB from 20 Hz to about 25 kHz, +5 dB at 30 kHz, +3 dB at 40 kHz, and +0.5 dB at 50 kHz. As with most of the other CD-4 cartridges, the resonant peak is at 30 kHz. Separation averages about 19 dB to 9 kHz, 17 dB at 10 kHz, and 11 dB at 20 kHz. This cartridge also has a very low IM distortion. Perhaps, like the Pickering, if some parameters could be altered, it too would be a superior cartridge. Musically, the Stanton 780/4DQ had some difficulties with loud organ bass passages and the high end was a bit strident. There was some distortion present in the mid-frequencies. The overall sound is a little hard. Evaluation was made with the dust brush attached to the cartridge, but compensated as described in the instructions.
Wt. 6.64 g; d.c. res. 655 ohms; Ind. 291 mH; Output 0.54 mV /1-cm/sec; IM dist: 1.2% lat., 1.7% vert.; Crosstalk-25 dB; Ch. Bal. 0 dB; Trackability: High freq. (10.8 kHz pulsed) 24 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) less than 20 cm/sec; Low freq. (400 + 4000 Hz lat. cut) less than 15 cm/sec. The diamond stylus is a Quadrahedral, similar to that used in the Pickering UV-15/2400-Q. $125.00.
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Victor 4MD-1X
This cartridge is considered to be the first CD-4 cartridge to be marketed. Although it has never been available in the U.S., it is still sold in Japan. The frequency response is flat from 40 Hz to above 16 kHz ± 2 dB, then climbs to +5 dB at 20 kHz and 28 kHz, down to +1 dB at 40 kHz and -1 dB at 50 kHz. Separation is 19 dB from 100 Hz to 10 kHz, dropping to 15 dB at 15 kHz and 9 dB at 20 kHz. Musically, we find it to be a bit muffled at the high end. The bass is adequate although some tracking difficulties were encountered in the pedal notes of the electronic and pipe organ. Transient response is somewhat muddy and there was some distortion in the mid-frequencies. Distortion was evident when reproducing music recorded on the Moog synthesizer.
Wt. 7.24 g; d.c. res. 446 ohms; Ind. 405 mH; Output 0.62 mV/1-cm/sec; IM dist. 1.3% lat., 6.8% vert.; Crosstalk -30 dB; Ch. Bal. 1 dB; Trackability: High freq. (10.8 kHz pulsed) 30 cm/sec; Mid-freq. (1000 + 1500 Hz lat. cut) 25 cm/sec; Low freq. (400 + 4000 Hz lat. cut) 24 cm/sec. The stylus is a nude diamond with the Shibata configuration. N.A. in U.S.
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(adapted from Audio magazine, Mar. 1974)
Also see:
Status: The CD-4 System (Jul. 1973)
The Evolution of Four-Channel Equipment (Jul. 1973)
Why You Should Buy Four-Channel Now (Jul. 1973)
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