Tweaking your Record-Player Page 8

With some arms—the SME V is one—the lower range of VTA adjustment may be limited by a tendency for the rear bottom surface of the arm to rub against the disc. If this seems to be preventing you from finding the correct VTA, you can get around it by using a small 1/16"- or 1/8"-thick block of aluminum to extend the cartridge farther below the arm. (The intervening spaces should be filled with damping mastic.) Every high-end dealer who's been in business for more than five years has a bin or two of arm and cartridge hardware, and will almost certainly have at least one shimming block among the rest of the junk. Don't use plastic ones, though; they couple poorly to the arm.

Tracking force
Because of the mechanical nature of the grooved-disc system, a playback stylus never maintains perfect contact with a modulated groove, but is constantly losing and regaining contact with one groove wall and then the other. Each time it regains contact, it puts a small click into the signal, and every amplifying stage in the system then acts to generate spurious energy from this. A short click has a large amount of ultrasonic energy—a pulse 1 microsecond long has a flat frequency content out almost to 1MHz—and nonlinearities in amplifying stages cause this HF content to intermodulate with signal frequencies to produce sum-and-difference components; the difference ones will "splatter" the sound of the clicks down into the range where they are very audible. This is the source of what we hear as mistracking—an overlay of hash, fuzz, or "airiness" riding on the musical signal.

You can never eliminate mistracking; the best one can hope for is to minimize it. Obviously, the less distortion there is in the system electronics, the less audible the mistracking will be. But for a given cartridge in a given arm, the only way of reducing it at its source is by increasing groove-contact force—upping the tracking force.

When one channel is consistently fuzzier than the other, suspect a tracking-force asymmetry. This can be due to azimuth tilt-angle misalignment, incorrect antiskate adjustment (in a pivoted arm), excessive horizontal-bearing friction, or insufficiently flexible tonearm wires. Tracking-force optimization should not be attempted until both pickup outputs are as closely matched in cleanness as possible.

It is commonly believed that increasing a pickup's tracking force causes a corresponding increase in the rate of record wear. This is not so. It's not tracking force that matters, it's contact pressure, and because vinyl has a certain amount of elasticity, increasing the tracking force causes the stylus to sink farther into the vinyl, thus increasing contact-surface area. The pressure increases much less rapidly than force. Yes, there is a point where excessive force will exceed the vinyl's elastic limit, causing permanent groove indenting, but with most elliptical styli, this apparently doesn't happen until tracking force exceeds about 2.25gm.

The thing that does the most damage to record grooves is cartridge mistracking. When a stylus is simply incapable of following the groove modulations, it exerts contact pressures hundreds of times higher than when tracking an unmodulated groove. The fact that a lousy cartridge may require 5gm of force to eliminate most mistracking is what gave rise to the idea that it was the high tracking force that ruined discs. It is, rather, the stylus's inability to stay with the grooves at any reasonable force that does the damage. With a cartridge that tracks fairly cleanly at up to 2gm, you should expect several hundred plays before a highly modulated disc is ready for the dustbin.

And when is a disc "worn out" anyway? Any heavily modulated LP will lose some audible cleanness with the first play on even the best and most carefully adjusted record player (footnote 11), but the amount of deterioration is much less on the second play, and diminishes almost exponentially thereafter. By the time it nears the end of its life, there is no audible sonic change from one play to the next, so it is impossible to say when it is "worn out." It may sound pretty sad, but 50 more plays probably won't make it sound much worse. For this reason, few discs ever get discarded for wear; they just get played less and less often (footnote 12), as the joy of the music becomes gradually more tempered by the irritation of the sound. (A caveat for buyers of used records.)

To measure tracking force, place the stylus on the gauge (or the hook as near to the stylus as you can get it), push the arm gently up, then down, and take the average of the two readings. This will allow you to get higher accuracy from high-friction gauges than you could by measuring in one direction only. Balance-beam types with plastic pivots tend to have the highest friction, beam balances with metal pivots are better, suspension types (with a hook at the end) are best if they're accurately calibrated. To check a gauge's accuracy, lay a new dime on top of the tonearm, centered right over the stylus tip, and adjust the tonearm force until the gauge reads exactly 2.27gm. Then remove the coin. The arm should now be perfectly balanced, exhibiting no downward or upward force at all. If it isn't, the scale may be miscalibrated.

Setting tracking force requires a certain amount of common sense. With most arm/cartridge combinations, you will nearly always find at least one nemesis in your record collection—a disc that always skips, usually on a drum stroke or electric bass note. Of all the LPs ever released, the Telarc Tchaikovsky 1812 Overture is probably the hardest to track. Its cannon blasts have been the undoing of countless top-line record players, not to mention the number of amplifiers and loudspeakers it has sent to Hi-Fi Heaven. So don't just blithely keep upping the tracking force until you can play every untrackable disc you own. If one or two discs in your collection skip, accept it philosophically. (If they always skip forward, or always start repeating, you might try readjusting the antiskate bias.) Consider also the possibility that a disc that has always skipped may have lost its intervening groove wall at that point, and has thus become completely untrackable regardless of what you do.



Footnote 11: This is why some perfectionists always make a cassette copy of the first time they play any new disc, and store the disc for safe keeping. The copy will never sound as good as the disc, but it will sound that way for more playings. And when it wears out, the disc is still almost new.

Footnote 12: Changing to a different cartridge can sometime work sonic wonders with old records, due to the new stylus riding on a different, relatively undamaged part of the groove wall. On the other hand, changing to a cartridge with a long-contact profile, Microridge or van den Hul, for example, can often increase surface noise and the reading of groove damage due to the stylus's being in contact with more of the groove wall.—JA

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