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Type: Moving iron.
Stylus: Contact line nude diamond.
Tracking Force: 1 gram.
Effective Tip Mass: 0.3 mg.
Cantilever: Single crystal sapphire.
Static Compliance: 30 x 10-6 cm/dyne.
Frequency Response: 20 to 20,000 Hz, ±1dB.
Channel Separation: 30 dB at 1 kHz, 20 dB from 500 Hz to 10 kHz.
Channel Difference: Less than 1 dB.
Voltage Output: More than 0.6 mV/ cm/S, rms.
Load Impedance per Channel: 47 kilohm.
Load Capacitance per Channel: 220 pF.
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Bang & Olufsen (B & O) has introduced a new series, MMC 20, of their moving-iron generating principle phono cartridges in a particular geometry called the moving micro cross (MMC), which transforms mechanical energy to electrical energy. In this series, unlike the previous models, the most important innovation is in the cantilever design. To increase the stiffness of the cantilever, B & O has departed from the usual aluminum or beryllium metals and introduced a cantilever formed from a single sapphire crystal. B & O claims that the single-crystal sapphire is 21 percent stiffer than beryllium and more than five times as stiff as aluminum.
The single-crystal sapphire, according to B & O, has a resonance beyond 20 kHz. Further, the velocity of sound in the single-crystal sapphire is twice that in aluminum, reducing any phase distortions at high frequencies.
The contact-line (CL) nude diamond stylus of the MMC 20CL phono cartridge is bonded to the tip of the single-crystal sapphire cantilever and is not replaceable by the user. The particular shape of the stylus gives a long contact in the vertical direction and a narrow line contact horizontally along the groove, thus providing a large overall contact area.
Although the MMC 20CL is designed for direct mounting (plug-in) into the B & O turntable tonearm, it comes with an adapter that permits it to be installed in any modern tonearm that uses half-inch spaced mounting centers.
A transparent plastic guard on the front of the cartridge is used to protect the stylus and at the same time permit the stylus to be seen for easy cueing. The MMC 20CL cartridge comes with a screwdriver, stylus balance, stylus brush, and the usual mounting hardware. Also included is a frequency response curve plotted for the individual cartridge as well as a computer-generated test printout for each individual cartridge showing its output, balance, separation, velocity, and 16-kHz level in comparison to the level at 1 kHz.
The MMC 20CL cartridge was mounted with its adapter in a Technics headshell and used with the Technics EPA-100, tonearm mounted on a Technics SP-10 Mk II turntable. We oriented the MMC 20CL in the headshell and tonearm with the Dennesen Geometric Soundtracktor. Although the cartridge is designed to track at one gram, it appears to be a little temperature sensitive so that at higher than normal room temperatures, the tracking force had to be increased by 200 mg. Our laboratory tests were conducted at an ambient temperature of 70° F, ± 1° (21.11° C) and the relative humidity was 73 percent, ± 3 percent. The tracking for all reported tests was at one gram, as recommended by B & O, and with an anti-skating force of 1.8 grams. The normal cartridge load of 47 kilohms in parallel with 250 pF capacitance was used for all the tests. As is our practice, measurements are made on both channels, but only the left channel is reported unless there is a problem in the right channel, when both channels will be reported for a given measurement.
Frequency response, using the Columbia STR-170 test record, is flat within +1.0,-1.7 dB from 40 Hz to 20 kHz, specifically +1 dB from 60 to 70 Hz, +0.5 dB from 100 to 1000 Hz, then dropping to-1.7 dB at 6 to 7 kHz,-1.25 dB at 10 kHz,-1 dB at 15 kHz, and-1.5 dB at 20 kHz. Separation is 24.75 dB at 1 kHz, 18 dB at 10 kHz, 16.5 dB at 15 kHz, and 16 dB at 20 kHz. From these data, one can conclude that the MMC 20CL has an excellent frequency response and a more than adequate high-frequency separation.
The response to a 1-kHz square wave shows a critically damped square wave with a very rapid rise time, no overshoot, and minimal ringing, with a stylus resonance of about 34 kHz. The cartridge-arm low-frequency resonance was at 14 Hz and of 1-dB amplitude with the Technics EPA-100 tone arm. The vertical resonance was about 12 Hz in the same arm.
The following test records were used in making the reported measurements: Micro-Acoustics TT-2002; Shure TTR-103, TTR-109, TTR-110, and TTR-115; Columbia STR-170, STR-100, STR-112, and SQT-1100; Deutsches Hi-Fi No. 2; Nippon Columbia Audio Technical Record (PCM) XL-7004, and Ortofon Direct-Cut Pickup Test Record 0001.
Wt., 4.1 g, 5.65 g with adapter; d.c. res., 678 ohms; ind., 228.5 mH; tracking force, 1.0 g; anti-skating force, 1.8 g; output, 0.82 mV/cm/S; IM distortion: (4:1) +9 dB lateral, 200/ 4000 Hz, 18 percent; +6 dB vertical, 200/4000 Hz, 16 percent; crosstalk (using Shure TTR-109), >30 dB; channel balance, within 0.1 dB; trackability: high freq. (10.8 kHz pulsed), 24 cm/S, mid-freq. (1000 + 1500 Hz, lat. cut), 25 cm/S, low freq. (400 + 4000 Hz, lat. cut), 19 cm/S; Deutsches Hi-Fi No. 2 300 Hz test band was tracked cleanly to 67 microns (0.0067 cm), lateral at 12.62 cm/S at +7.5 dB and 55.4 microns (0.00554 cm), vertical at 10.32 cm/S at +5.86 dB. Surprisingly, slight mistracking was noticeable at 70 microns, but was not harsh in nature.
The MMC 20CL was able to play all the tracking and transient ability bands on the Micro-Acoustics TT-2002 musical test record. The Shure Obstacle Course Era Ill test record caused the cartridge no difficulty until level 5 of the solo violin where the beginning of distortion was just evident.
Unfortunately, the MMC 20CL was unable to track beyond level 4 of any band of the Shure Obstacle Course Era IV. This is not uncommon inasmuch as very few cartridges can track this musical test record beyond level 4 of any band.
Use and Listening Tests
As usual, we performed our listening tests both before and after measurement. We found the cartridge to be neutral in performance, adding no coloration to the music being played. We were unable to hear any distortion in the records we played, with their varying recorded velocities. The MMC 20CL appears to favor the human voice, in particular the soprano. We were especially impressed with the cartridge's ability to cleanly reproduce the cannon fire on the Telarc 10041 Tchaikovsky: "1812" Overture, op. 49 recording and the 19.2-Hz organ pedal (held for 55 seconds) in the Franck: Pastorale in E Major as recorded on the Hammond Castle Pipe Organ by Decibel Records DB 1000 (Box 631, Lexington, MA 02173). If you cannot hear the 19.2-Hz pedal, remove the grill cloth on your speakers and watch the cone vibrate at this low frequency.
After an extended period of listening to the B & O MMC 20CL phono cartridge, it becomes obvious that its reproduction of music is excellent despite what some laboratory findings might indicate. Not infrequently, we wonder if laboratory measurements really tell us anything about how a phono cartridge will sound.
Evaluation Equipment and Records
The following equipment and specific records listed below, as well as many discs listed in past reports, were utilized in the listening evaluation of the MMC 20CL phono cartridge: Technics SP-10 Mk II turntable, Technics EPA-100 tonearm, Nikko Beta 1 preamplifier, Crown IC-150A preamplifier, Audire DM 700 power amplifier, Audio Innovations LED 2C Dynamic Power Display, Columbia SQL-400A SQ decoder, and a pair of stacked Duntech DL-15B speakers in each channel. Each pair of speakers was connected to the Audire DM-700 power amplifier with Monster Cable. The turntable was equipped with the Hiraoka Disk-SE22 turntable mat.
The following records were among those used to aurally assess the performance of the B & O MMC 20CL phono cartridge:
Hammond Castle Pipe Organ (Vol. 1), D. Marshall (organist) Decibel Records ( Box 631, Lexington, MA 02173) DB 1000.
Offenbach: La Perichole (Crespin, Vanzo, Bastin), Lombard, Strasbourg Philharmonic Orchestra RCA (Erato) FRL 2-5994.
Lehar: The Merry Widow (Sutherland), Bonynge, National Philharmonic Orchestra London OSA 1172.
La Stupendal (Sutherland) London OS 26603.
Concert, Welch (organist) -- Wilson Audio Specialities ( 147 San Felipe Way, Novato, CA 94947) H-I-77.
Berg: Lulu (Silja), Dohnányi, Vienna Philharmonic London OSA 13120. Strauss, R.: Ein Heldenleben, Solti, Vienna Philharmonic -- London CS 7083.
Brahms: A German Requiem (Kanawa, Weikl), Solti, Chicago Symphony Orchestra and Chorus--London OSA 12114.
Direct to Disc
Sonic Fireworks (Vol. 1), Morris, Atlanta Brass Ensemble -- Crystal Clear Records CCS-7010.
Sonic Fireworks (Vol. 2), Morris, Atlanta Brass Ensemble--Crystal Clear Records CCS-7011.
Taj Mahal, Live and Direct-Crystal Clear Records CCX-5011.
The Dillards: Mountain Rock-Crystal Clear Records CCS-5007.
The Power and the Glory (Vol. 2), Holzgraf (organist)-M & K RealTime Records RT-113.
The Magnificent Basso (Li-Paz)-M & K RealTime Records RT-102.
Pulse Code Modulation (PCM), Digital to Analog
Tchaikovsky: 1812; Capriccio Italien; "Cossack Dance" from Mazeppa, Kuzel, Cincinnati Symphony Orchestra--Telarc Digital DG-10041.
Moussorgsky: Pictures at an Exhibition/Night on Bald Mountain, Maazel, Cleveland Orchestra--Telarc Digital 10042.
Naturally, Mel Lewis, The Jazz Orchestra--Telarc Digital DG-10044.
Mehta Conducts Mahler: Symphony No. 4 in G Major, Israel Philharmonic Orchestra-- London Digital Recording LDR10004.
Mendelssohn: Symphony No. 4, "Italian," Dohnányi, Vienna Philharmonic London Digital Recording LDR10003.
Tchaikovsky: Symphony No. 4, Maazel, Cleveland Orchestra Telarc Digital 10047.
Bartók: Concerto for Orchestra, Ormandy, Philadelphia Orchestra RCA Digital ARC1-3421.
Beethoven: String Quartets Nos. 3 and 6, Smetana Quartet Denon OX-7138N D.
Tchaikovsky: Symphony No. 4 in F Minor, op. 36, Sanderling, Berlin Symphony Orchestra Denon OX-7137-N D.
The Works of Workman, Reggie Workman Denon YX-7539-ND. Live in Tokyo, Archie Shepp Quartet Denon YX-7538-N D.
Anthem for the New Nations, Dollar Brand Denon YX-7537-N D.
Round Midnight, Dave Burrell Denon YX-7541-ND.
Gon's Delight, Takashi Mizuhashi and His Friends Denon YX-7540-ND.
Denon records are distributed by American Audioport, Inc., Columbia, Mo., 65201, USA.
(Source: Audio magazine, Mar. 1980)
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