Tweaking your Record-Player Page 2

Second, minimal resonance. If you're at all interested in accuracy—in hearing what is actually on a recording rather than a glorification of it—minimal resonance is always better than "controlled" or "dissipated" resonance. That is, it's better to have a tonearm which hardly resonates at all than one whose design embodies clever ways of getting rid of resonances. It also means the platter should have a vacuum-clamping system to hold discs firmly and unequivocally during play, against an underlying surface soft enough that it won't embed dust particles into the grooves, on a platter dense enough to soak up the vinyl resonances. Owners of SOTA turntables are ahead of the game here, as a vacuum holddown can be retrofitted to any of SOTA's last several models. So-called disc stabilizers are better than nothing, but they vary widely in efficacy, and are more useful for modifying disc resonances than in eliminating them. A clamp that hikes the rim of a disc above the edge of the platter is worse than no clamp at all.

Third, minimal resistance to groove modulations. The more the stylus resists deflection, the more tracking force it will require to stay in contact with the groove walls and the faster it will wear records. Through most of the audio range, trackability is a function of stylus compliance, which should never be much below 15cu (compliance units; 1cu = 0.000001 cm/dyne) or above 20cu. At high frequencies, the limiting factor is effective tip inertia or mass, which should be as low as possible (0.4mg or less; definitely less).

Fourth, maximal tracking symmetry. This means that every aspect of the stylus/groove relationship—tangency error, verticality, and distribution of tracking force between the groove walls—should be as symmetrical as possible. Small discrepancies here are inevitable, but the more they're minimized, the better the signal qualities from both channels will match and the better the overall performance will be. For example, channel separation is greatest when the axes of the cartridge's sensing (transducing) elements are at precise right angles to the groove walls.

Fifth, minimal microphonics (acoustic feedback). A cartridge resting on a disc acts like a microphone, picking up any sound vibrations which get to it from the loudspeakers. Sound vibrations can reach the disc through the air or through the structure of the listening room (the floor, usually), and the effect can range from a slight smearing of sonic detail to gross exaggeration and muddying of bass. Anything which reduces disc resonance will also reduce airborne microphonics, but only a good suspension system (or a turntable stand rising from the basement floor) will have any effect on structure-borne feedback.

And sixth, optimal system resonance, both in terms of frequency and damping. The so-called system resonance is a result of the stylus compliance and the effective arm-cartridge mass—the mass right at the stylus. If this has a frequency within the audio range, the player will frequently skip grooves on certain bass notes; if it occurs too far below the audible range, the resonance will exaggerate the energy produced by disc warps and eccentricities, causing severe woofer-cone pumping. This wastes amplifier power and impairs imaging and soundstaging. System resonance should ideally occur at around 12Hz, almost one octave below the bottom limit of audible bass frequencies—20Hz—and one octave above the frequency where warps have their maximum energy, around 6Hz.

Other things like extraordinary platter-rotation smoothness and AC-supply cleanness and regulation have been shown to affect LP sound, but the improvements here are small enough that they will probably not be noticed until after the four above-listed priorities have been met.

Tooling up
This article assumes that you have bought your last turntable with tonearm installed or have had it installed by the dealer. I will therefore concentrate on how to install the cartridge optimally, assuming that this has not been done by the dealer, and how to tweak—I mean adjust—the overall player to enable it to give of its best.

To do any adjustments to your record player, you will need the following: a small bubble level; a nonmagnetic, low-friction stylus-force gauge; a tangency template or jig; a #2 or #3 jeweler's chisel-tip screwdriver; whatever tool is required to make sure the turntable is level; a flat mirror about 2" by 3"; some round wooden toothpicks; a pair of small needle-nose pliers; serrated-tip tweezers; a selection of different-sized insulated ("spaghetti") sleeves; and a tube of any household glue except Miracle Cement or Super Glue (cyanoacrylate) (footnote 4). You will also need a wearable binocular magnifier or a pair of strong reading glasses (footnote 5) if you aren't nearsighted.

If you don't already own a circular spirit level, shame! All turntables should be set up to be level. You can buy these from any audio store, and you should choose the largest one they have, because the larger its base, the more accurately it will read (footnote 6).

Scouting the territory
Before doing anything, determine where in your listening room you're going to put the phono unit. If you can't go with a masonry column planted firmly on the planetary surface and sticking up through the floor, don't just settle for an unused endtable; many high-end turntables have almost as bad shock isolation as their cheap-and-dirty mid-fi cousins. Consider buying an isolation stand, like Arcici's Lead Balloon or the Merrill Stable Table (footnote 7). This should be spiked to the floor, because its efficacy depends on its not being free to vibrate on its own.

Normally, the turntable unit should be placed to the right of the system's preamp/control unit, to get the cartridge as far as possible from hum-inducing power transformers (assuming that these are positioned at the left of the preamp's chassis), but there are exceptions to this rule. Turntable output leads should not exceed about 1 meter (39") in length, particularly with MM cartridges, and if the preamp's phono inputs are at the far left (as seen from the front), right-hand turntable placement may not allow them to span the distance.

Footnote 4: These glues do not fill gaps; they require tightly abutting surfaces in order to work properly.

Footnote 5: Binocular magnifiers sell for around $30 in large hardware stores, hobby shops, and some optical-supply houses, but high-magnification reading glasses cost about a third as much. These can be found on a rotating display rack in many supermarkets, usually near the prescriptions counter. Look for one marked +2.75 diopters, or "Strength" # 12. (You'll find a mirror located at the top of the rack; make sure the eyeglass frames are flattering if you plan to wear them on safari.)

Footnote 6: I find a small, rectangular, lightweight, aluminum-frame bubble level to be best, its long axis enabling very fine adjustments to be made. When adjusting the turntable springs of a subchassis turntable to level the platter (once the table itself is level), it is important to have an LP sitting on the platter and to place the level at the center of gravity of the tonearm/subchassis/platter/LP system.—JA

Footnote 7: Target, distributed in the US by May Audio Marketing, makes an excellent wall shelf to isolate turntables from floor-borne vibration. (See the Audio Advisor's ad in this issue.) I bought one a year or so ago and have been impressed by the resultant sonics. Target also makes good floor-standing tables, as does The Sound Organisation.—JA