Audio & Design M9BA tonearm Manufacturer's Comment and Follow-Up

Manufacturer's Comment

We are gratified to note that The Stereophile observed the same improvements when using the A&D tonearm that we observed.

As for the minor criticisms aimed at the arm that was tested, we should emphasize the point that nothing is perfect. The arm was put into production simply when it was because even with its "faults," it had proven to be better than any other arm that was available and it was felt that such an improvement in pickup performance was more than adequate justification for putting the arm on the market.

The aim that The Stereophile tested was one of the first production units. Even before the Stereophile report was completed, we had recognized, and taken steps to correct, the things for which Stereophile criticized the arm. The adjustment and operation of the lift lever have been made more positive on later models, and the output cables have been lengthened and reduced in total capacitance.

A&D have also recently introduced an experimental model of carrier arm designed specifically for Decca plug-in pickups, and initial tests have proven most promising.

Follow-Up, from December 1970, Vol.2 No.11

Nominal length: 9". Rear overhang: 2.5". Distance from turntable center: to center of adjustable base, 8.5".

Mounting: By cutting a rectangular hole and drilling four holes for the retaining bolts, which are provided by knurled screws. Exact accuracy of positioning is not essential, as the arm is fitted with an adjustable sliding base which can be locked into the desired calibrated position with a lever. Exact overhang achieved in conjunction with an alignment protractor supplied. No tools are required for the setting-up operation; each adjustable component locks into position with miniature levers. The arm features small, accurate mercury baths, through which electrical contact is made, in place of conventional lead-out wires. It is necessary to fill these with the small dropper supplied. Once the mercury has been installed (a simple job), the arm should not be transported except with great care.

Cartridge acceptance: Restricted to cartridges weighing between 5 and 8gm, and tracking up to a force of 1.5gm. with the light counterweight supplied. (Alternative heavy counterweight available for cartridges between 9 and 17gm.)

Headshell: This is not detachable, as the whole top arm can be lifted off the mercury contacts in order to fit the cartridge. The headshell has parallel lines engraved on its underside to assist the user in lining up the cartridge correctly when screwing it in, and the headshell can be twisted on the arm tube to ensure that the stylus is truly vertical in the groove when viewed from the front. Separate "carrier arm" assemblies are available. Height adjustment: The arm as supplied can be used with turntables from 1.25" to 2.5" high. A pre-cut mounting board is available for the Thorens TD-124 or TD-125.

Lifting device: A damped lever-operated device is integral with the pillar.

Leads: The length of leads supplied, which do not unplug from the base, was 36", and the capacitance per channel measured 150pF.

Lateral balance: Achieved by twisting the eccentric counterweight assembly on its compliant mounting, and due to the design arid high polish on the hub and pillar, it was simple to set accurately.

Damping: Viscous-damping fluid is applied to the pivot in a unique manner. A dashpot arrangement provides a very high degree of torsional damping to the unipivot without impeding lateral movement. The arrangement works admirably in all respects, but it is not easy to remove the fluid for transportation. The counterweight assembly is also decoupled, and in all, the arm was very well protected from shock and any tendency to accentuate rumble or acoustic feedback.

Stylus force: This is applied by turning a calibrated screw at the rear of the counterweight after initial balancing, each turn representing 0.25gm. This proved to be very accurate and simple to use.

Bias compensation: This is achieved by magnetic attraction of the upper moving electrodes in the mercury baths and is therefore friction-free. There is no provision for adjustment, and the compensation was found to be hopelessly ineffective for tracking forces of more than 0.5gm, and even then was quite inadequate towards the center of the disc. Nevertheless, the small amount of correction that this arm provides, for the intended very-low tracking forces, is far better than adding any device which could cause additional friction.

Friction: The arm uses a hardened, ground and polished unipivot over which sits a miniature ball-bearing race. Since there are no lead-out wires, the friction we measured was purely the starting friction of this single micro-bearing assembly, which was very low indeed. So much so, in fact, that with the viscous fluid omitted, and the arm perfectly balanced, the movement of air in the room disturbed the arm. Nevertheless, we found a very slight variation in friction across different parts of the record, presumably due to extremely minor variations in bearing polish at different spots. However, at its worst point, the friction was a mere 5mg laterally and 5.5mg vertically. For all practical purposes, these orders of friction can be considered inconsequential, and the arm has no internal wiring to resist further the movement of the arm.

Effective mass: Partly because of the absence of a headshell plug and socket (since this part is not removable), the effective mass was very low at just under 10gm, and suitable for the most compliant cartridges currently available or likely to become available for some time.

Comments: Obviously a specialized product which, while requiring respect in handling, is really quite easy to set up accurately and use (footnote 2). The general standard of workmanship is good, although we did have to reject our first sample as obviously faulty because of an assembly error that would not allow it to traverse the whole of the record. In most aspects of performance it is nearing perfection, but with the inadequate bias arrangements, the arm will only realize its full potential with cartridges capable of tracking at very low forces. Indeed, if it ever becomes feasible to track at less than 0.5gm, this may be one of the very few arms to cope with the situation.—John Wright (footnote 3)

Footnote 2: This is a matter of opinion. Ye Ed.

Footnote 3: John Wright was involved in the design of this tonearm.—Ed.

Ortofan's picture

... the hazard of micromercurialism had been identified 50 years earlier, that this product was ever put into production.

John Atkinson's picture
Ortofan wrote:
the hazard of micromercurialism had been identified 50 years earlier . . .

In the mid-1960s, in a high-school science class, I made a barometer by filling a long tube that was closed at one end with mercury, then inverting it into an open container of mercury! Thank goodness mercury has a very low vapor pressure.

John Atkinson
Technical Editor, Stereophile

Bogolu Haranath's picture

"Under Pressure" ......... Queen (Freddie Mercury) & David Bowie :-) ..........

Kal Rubinson's picture

My favorite arm and I am still sad that I butchered it when I was in my "modify everything" phase. I bought it directly from John Wright.

Still have a few remnants in my parts bin to remind me of my sins.

Ortofan's picture

... back in that era which I preferred was the Grace G-707.

Bogolu Haranath's picture

May be the happy (old) days are here again .......... Check out the new Schiit Audio SOL turntable for $799 :-) ..........

Ortofan's picture

... Sol turntable, plus at least another $200-300 for a phono cartridge and preamp, then why not simply buy the all-in-one Technics SL-1500C for $1200?

Bogolu Haranath's picture

Made in good old US of A :-) ...........

Ortofan's picture

... set-up video for the Schiit Sol?

Bogolu Haranath's picture

No S**** ........ That Technics table may be a better value for the money ......... That Technics table is featured in AnalogPlanet video ....... Looks like Stereophile may be reviewing that Technics TT ....... BTW ..... AD may be able to handle that S**** :-) ........

Thorp’s Dave's picture

A historical note. As a sixth form school student I assembled most of these that were exported to the US from ‘66 to ‘68. Worked weekends for John and his team.
It’s good to know that these gave much pleasure.