Manufacturer's Specifications:
Tonearm:
Overall Length: 11 9/16 in. to 12 3/8 in. (293 mm to 321 mm), depending on counterweight position.
Effective Length: 9-5/16 in. (237 mm).
Angle of Rotation: Approximately 80°.
Balance and Tracking-Force Adjustment: Static balance; tracking force adjustable in 0.1-gram steps.
Output Cable: Plug-in, molded type.
Capacitance: 86 pF, including cable.
Headshell: Plug-in, lightweight (approximately 6 grams).
Range of Usable Cartridge Weights: 4 to 10 grams; 10 to 17 grams with optional J weight.
Price: $300; J weight, $12.
Phono Cartridge:
Type: Moving magnet.
Frequency Response: 10 Hz to 47 kHz, ±2 dB.
Output: 3.75 mV at 5 cm/S at 1 kHz.
Separation: 30 dB at 1 kHz.
Stylus Force Range: 0.5 to 2 grams; recommended stylus force, 1.5 grams.
Compliance: 20 x 10^-6 cm/dyne.
Impedance: 1.7 kilohms at 1 kHz.
Suggested Load Resistance: 47 kilohms.
Recommended Total Load Capacitance: 200 pF.
Price: $200; replacement stylus, $100.
Company Address: c/o Sumiko, P.O. Box 5046, Berkeley, Cal. 94705.
In the early 1970s, when CD-4 discrete four-channel records were being produced, much work was done by cartridge and tonearm manufacturers, including Grace, to extend high-frequency response so that the carrier system used for the rear-channel information could be transduced properly. This led to many improvements in phono cartridges and tonearms. The CD-4 system is no longer with us, but the research that was done for it continues to yield sonic benefits. The ability to reproduce wide-band signals has resulted in more transparent sound, as evidenced by the Grace G-747 tonearm.
The G-747 has been a favorite of many audiophiles, for very good reasons: It uses simple, proven design principles and high-quality materials, and in this era of very expensive tonearms, it offers an alternative to taking out a second mortgage on your house. The G-747 is a good choice for use with many of the excellent moving-magnet cartridges offered by various manufacturers. Since the Grace F-9E Super cartridge is particularly well matched to the G-747 tonearm, I used this cartridge for most tests of the G-747.
Other cartridges were also used during the evaluation, with good results.
Grace has been making moving-magnet cartridges for some time, and a few years ago, the audiophile community became aware that the company's F-9E was an outstanding example of the type. The F-9E Super is an upgraded version of this cartridge. The damping material has been improved so that tracking is better at the lower and middle frequencies, without a sacrifice of high-frequency performance. The inductance of the coils has been reduced; this is good because it raises the electrical high-frequency resonance (when loaded by the same capacitance as the earlier model), giving the F-9E Super more extended high-end response. Reducing the number of turns of wire in the coils (to lower the cartridge's inductance and resistance) also reduces the output; to compensate, a samarium cobalt magnet, with greater magnetic force for a given mass than Alnico V, is used.
The stylus has been improved as well. Like previous Grace cartridges, the F-9E Super uses Ogura Vital diamonds, made from rectangular rather than square blocks of diamond, to reduce tip mass. In the F-9E, the diamond's grain has been reoriented so that the hardest part of the stylus contacts the record groove. This should yield even longer stylus life.
The first thing I noticed about the G-747 arm was that the mounting system requires only a single hole in the mounting board; the tonearm pillar is locked to the bottom of the mounting board by a single, large hex nut. This makes installation very easy. A template is supplied to ensure accurate positioning of the tonearm with respect to the turntable's center spindle.
Fig. 1--Frequency response and interchannel crosstalk of arm and cartridge,
using B & K 2010 test record. Note unusually close matching between channels.
Fig. 2--Low-frequency tonearm/cartridge resonance is at 6 Hz, with a Q of
4.6, using B & K 2010 test record.
Fig. 3--Tonearm resonance check, using slow sweep from 20 Hz to 1 kHz.
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MEASURED DATA
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The G-747 has precision-jeweled gimbals for both vertical and lateral pivots. When I tried to push and pull the tonearm pipe to see if there was any looseness in the bearings, I couldn't feel any at all, and this is as it should be.
The tonearm pipe, counterweight, pillar and special-alloy headshell are finished in black. The calibration marks on the rotatable counterweight are white, with a red reference line on the fixed tube. The armrest and sidethrust compensator are on a small platform which encircles the main pillar. The thin, straight tonearm pipe has very little sound of its own when tapped. A separate headshell makes mounting and adjusting different cartridges easy; when changing cartridges, only the tracking force must be reset.
The G-747 is statically balanced. The same counterweight is used to balance the arm and to set the tracking force; the tonearm's dynamic mass seems low enough to employ this method with good results. After the arm is balanced for a given cartridge by adjusting the counterweight, a calibrated ring on the weight is adjusted until its zero mark is at the red reference line on the arm tube. The tracking force is then set by rotating the counterweight toward the pillar until the number on the ring that represents the desired tracking force is lined up with the red mark. I found the calibration to be very accurate, with an error of no more than 0.1 gram. The height of the main arm pillar is adjustable over a range of about 1.8 inches to accommodate turntable platters and cartridges of varying heights.
The sidethrust compensation is set by moving a counterweight on a small lever which is attached to the rear of the arm pipe by a thread. The lever, which has calibration marks, is pivoted so that as the tonearm moves toward the center of the record, the weight is slowly raised. The integral armrest has a friction-fit clamp which holds the tonearm pipe securely. The cueing mechanism, used to lower and raise the tonearm, is damped; if the arm is dropped accidentally, it will not damage a record.
The headshell is made of lightweight aluminum--a good choice, because it is rigid as well as very low in mass. Since the cartridge and headshell are at the end of the tonearm, their mass affects performance greatly. For best performance, any necessary mass should be as near the pivots as possible. This can be achieved with the counterweight, but the cartridge and headshell must be at a distance from the pivots and so should be as light as possible. The F-9E Super cartridge weighs 6.9 grams, which is moderate for a moving-magnet type.
Fig. 4--Output of tonearm due to mechanical impulse applied to arm tube,
with arm on rest but not locked. Total time period is 20.47 mS.
Fig. 5--Spectral analysis of tonearm output due to mechanical impulses,
with 16 impulses applied and averaged. Output in the 1.9 to 3-kHz region
could make the sound seem "forward."
Fig. 6--Interchannel phase of cartridge, using B & K 2011 test record,
band 7, pink noise.
Measurements and Listening Tests
The smooth, open sound quality of the F-9E Super cartridge is verified by the data for amplitude versus frequency response, shown in Fig. 1. The results are for the B & K 2010 test record, which has a top frequency of 45 kHz. I use this record because it has extended response above 20 kHz and very low crosstalk above 200 Hz; however, it has a slight droop above 15 kHz, which accounts for some of the roll-off shown. I also used the JVC TRS-1007 sweep test record, which has a very uniform response up to 20 kHz.
With this disc, the F-9E Super's output is actually flat to 20 kHz, but the important thing to note is the smooth, gradual roll-off. This is a characteristic of excellent practical high frequency amplitude and phase response; more extended response could cause problems for some preamps. Some of the comments made by the listening panel, while not mentioning it directly, could be related to the smooth, extended high-frequency response of this Grace combination.
For instance, it was felt that the sound of brushes on drums was very realistic.
The extremely low crosstalk between channels, especially at the higher frequencies, is amazing. I think this has much to do with the cartridge's clarity. While Fig. 1 does not show this, due to the B & K test record's roll-off, tests made with the JVC record show that the small amount of crosstalk above 20 kHz centers around 34.5 kHz; this is the usual high-frequency resonance caused by the stylus mass interacting with the compliance of the record material. The crosstalk in the low-frequency range seems to be an artifact of the test record itself, since it appears in every test I have ever done with that record. (With the other test records I use, low-frequency crosstalk is at a much lower level. Figure 1 does, however, allow comparison with other cartridge/ tonearm combinations which I have tested in the past.) The low-frequency resonance caused by the interaction of the tonearm's dynamic mass and the cartridge's compliance is shown in Fig. 2. This resonance is at 6 Hz, lower than some experts recommend, but I think it would only be a problem with badly warped or off-center records, since it appears to be fairly well controlled. Except for occasional problem records like these, such low-frequency extension is an advantage, since it gives the bass, in the audible band, a more uniform frequency and phase response. The bass was considered very good by the listening panel, albeit a bit less damped than the reference system's. The sound of guitar, for example, was thought to be a bit "fuller" than on the reference system.
Figure 3 shows the results of a slow sweep from 20 Hz to 1 kHz and is meant to reveal any tonearm resonances. This is an excellent result for a system with a detachable head shell. The fit of the headshell to the arm pipe is very good, and the locking screw appears to do a good job. There are slight discontinuities in the response of the right channel at 80 Hz and 120 Hz. It seems a small price to pay for the convenience of being able to use different cartridges.
Another indication of the way the tonearm deals with mechanical energy is shown in Figs. 4 and 5. The amplitude-versus-time trace of Fig. 4 shows that when a mechanical impulse is applied to the tonearm, the vibrations produced are damped very quickly. A tiny replica of the initial impulse appears as delayed energy later on the trace. While the total energy of this delayed signal is very low, it is possible that it could reduce clarity or increase brightness.
This is because 'delayed signals tend to stand out unless they are covered up by other signals loud enough to mask them. A spectral analysis of the arm's response to mechanical impulses (Fig. 5) reveals energy between 1.9 and 3 kHz, which would tend to make the sound a bit brighter or more forward. In both Figs. 4 and 5, the mechanical impulse to the tonearm is being picked up by the cartridge directly, not through the stylus. The energy shown in Fig. 5 is at least 40 dB below the 10-cm/S reference level. This level is much higher than what would actually be produced by even the most heavily cut record. The graph should be used only as an indication of the relative levels of spectral energy and not as a measurement of absolute level. Figure 4 shows that the energy is well controlled by the G-747 tonearm, and that there is no tendency to vibrate at any particular frequency.
Figure 5 confirms this, since the spectrum is relatively uniform, with no spikes of energy.
The ability of the F-9E Super cartridge and G-747 tonearm to reproduce stereo spaciousness and imaging exactly as it was recorded, without adding or subtracting anything, is demonstrated by the data shown in Figs. 6 and 7. The listening panel's comments about the excellent stereo image tended toward the conclusion that there wasn't much difference between that of the Grace combination and the reference system. If there was any indication of a difference, it was at the highest frequencies, where the sound of the Grace combination seemed a little bit less smeared between the speakers. This was apparent only on rare occasions, however.
Fig. 7--Interchannel phase of tonearm and cartridge as a function of frequency
(B & K 2011, band 7, pink noise). Phase difference at 20 kHz is 16.6°
(2.3 µS).
Fig. 8--Tracking of arm and cartridge at 1 kHz, 20 cm/S. Note slight mistracking
at this level.
Fig. 9--Spectral components of 1-kHz signal shown in Fig. 8. Level of third
harmonic (3 kHz) is 1.6% in the left channel and 1.1% in the right (1.0%
equals -40 dB).
Fig. 10--Arm/cartridge output at 30 and 15 cm/S, 10.8-kHz pulse test. Note
the small amount of asymmetry and absence of compression even at 30 cm/S,
a very high level.
Fig. 11--Spectrum of distortion products for 30and 15-cm/S signals shown
in Fig. 10. Level at 250 Hz is about 30 dB down for 30-cm/S signal, representing
distortion of about 3%.
Fig. 12--Arm/cartridge output for 1-kHz square wave, CBS STR-112 test record.
The F-9E Super and G-747 did very well when playing highly modulated recordings, especially those with big bass-drum sounds. The data in Fig. 8 shows the output waveform produced by a 1-kHz tone from the B & K 2010 test recording. The level was 20 cm/S, which is the second highest on the record. This is a very good waveform, and the distortion spectrum shown in Fig. 9 confirms this. The third-harmonic distortion for this 20-cm/S level is 1.6% in the left channel and 1.1% in the right channel. The level of the ninth and tenth harmonics is almost 50 dB down from the reference level of 10 cm/S. The slight increase of output at these harmonics might add a tiny bit of "sizzle" to the sound, and indeed, one panel member commented to that effect when comparing the sound of the Grace arm and cartridge with that of the reference system.
The response of the Grace combination to the 10.8-kHz tone-burst signal of the Shure TTR-103 test record can be seen in Fig. 10. This also shows very good performance, with only a small amount of asymmetry and no indication of compression. This means that the Grace combination will reproduce the dynamic peaks of music without making them sound muted. The slight asymmetry is responsible for the lower frequency spectral components shown in Fig. 11.
The upper waveform of Fig. 10 is related to the upper spectrum of Fig. 11, and the lower waveform of Fig. 10 is related to the lower spectrum of Fig. 11. The upper spectrum of Fig. 11 shows that the output at 250 Hz is down about 30 dB, which represents 3% distortion. The level of the 10.8-kHz signal which produced the data in the upper parts of Figs. 10 and 11 is 30 cm/S, which is the highest level on the Shure TTR-103 test record. The ability of the Grace combination to accurately trace this signal indicates that high-level musical overtones will cause very few problems. Any mistracking in this region would tend to cause coloration in lower parts of the spectrum. The comments by the listening panel didn't indicate any problems due to such high-frequency mistracking.
The output of the Grace combination for the 1-kHz square wave of the CBS STR-112 test record is shown by the digital storage oscilloscope trace of Fig. 12. The slight dip near the start of the top of the square wave correlates with the high frequency roll-off shown in Fig. 1. The shape of the square wave compares favorably with that from other top-quality cartridges. Tests for absolute polarity indicate that the Grace combination follows the convention adopted for CD-4 four-channel recordings. This calls for the cartridge to produce a positive output when the groove wall is modulated toward the outside of the record. Most cartridges seem to follow this convention.
The G-747's pivots have very low friction, well below the 40-mg limit of my measuring system. I did note that the G747 allowed the F-9E Super cartridge to do a good job of reproducing some warped records, at a maximum tracking force of 1.8 grams.
Conclusions
The Grace F-9E Super cartridge and G-747 tonearm make an excellent combination and compare favorably to my reference system-especially in the high-frequency range, where the Grace system was a bit better. The stereo presentation was as good as any combination I've tested; comments from the listening panel confirmed this. The moderate cost for such high performance is another strong reason for me to recommend that you audition this cartridge and tonearm.
The G-747 tonearm is suitable for use with most moving magnet or moving-coil cartridges of moderate weight and compliance. The fact that it has a lightweight, removable headshell may also be a strong consideration for people who would like to interchange cartridges from time to time.
The ease of rebalancing and resetting the tracking force for different cartridges makes the G-747 a good choice.
--Edward M. Long
(Source: Audio magazine, Jan. 1986)
Also see: Technics EPC-205CMk4 Cartridge (Jan. 1986)
Grace F-9E Ruby Phono Cartridge (July 1983)
Goldmund ST4 Turntable & Gold Cartridge (Aug. 1990)
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