Pattinaggio e anti-pattinaggio: le basi
C'è molta confusione sulle forze di skating e sulla compensazione anti-skating tra gli audiofili e persino nei media specializzati. Ci sono stati stimati produttori di bracci che hanno affermato che le forze di skating non sono abbastanza importanti da gestire o che qualsiasi compensazione anti-skating influirà negativamente sulle prestazioni. Ci sono state - e ci sono ancora - spiegazioni errate sullo skating/anti-skating su diversi siti web di audiofili e produttori di bracci.
Anche quando le spiegazioni sono accurate, spesso sono formulate con una terminologia poco familiare a chi non ha una solida conoscenza della fisica. WAM Engineering propone una semplice analogia che faciliterà la comprensione delle forze di slittamento. Non entreremo nei MOTIVI delle forze di slittamento e delle loro cause, poiché è proprio lì che spesso ci si addormenta. Invece, proponiamo uno scenario che molti di voi hanno sperimentato e che speriamo possa aiutarvi a comprendere cosa sia in gioco.
L'ESEMPIO
Hai mai praticato sci nautico o wakeboard? Se sì, probabilmente ricorderai che, mentre sei trainato dalla barca, il punto più facile per sciare e che richiede la minima quantità di energia per mantenere la posizione si trova proprio sopra una linea retta definita dalla direzione della barca, DIRETTAMENTE dietro la barca. Quando ti sposti da un lato o dall'altro della scia e cerchi di mantenere la posizione al di fuori della scia della barca, devi spendere energia per resistere alla forza che cerca di riportarti su quella linea retta che corre direttamente dietro la barca nella sua direzione di marcia.
La forza che ti tira indietro verso il punto direttamente dietro la barca è una forza che ti fa pattinare . Il tuo sforzo di allontanarti da quella forza, inclinandoti bruscamente in una direzione in modo da rimanere ben al di fuori della scia, è una forza che ti fa pattinare .
Una forza di skating significativa non è generata dall'angolo di offset, come spesso erroneamente si sostiene, ma è principalmente una funzione dell'attrito generato nel solco dallo stilo e dalla posizione del punto di articolazione del braccio, che NON si trova sulla linea retta definita dalla tangente al solco tracciata dallo stilo. ( Una tangente a un cerchio è una linea che tocca appena un cerchio in un punto e dove una linea tracciata in quel punto fino al centro del cerchio è perpendicolare alla linea. )
Imagine that the tonearm pivot point is the boat, the stylus is the skier and a line defined by the tonearm pivot point and the spindle is the center line of the wake of the boat. As the distance between the stylus (skier) and the straight line defined by the pivot point and the spindle (center of the boat wake) increases, skating forces also increase. As the skier moves back toward the center of the wake, skating forces decrease until they reach zero in the center of the wake.
While the above description of skating force in vinyl playback is incomplete, it is certainly sufficient for purposes of making the general principles more accessible to the average audiophile. Videos to help you understand it in its entirety coming very soon!
WATCH SKATING FORCE IN ACTION - *EXTREME CAUTION REQUIRED*
If you have a record with no grooves or run out grooves pressed on it you can see this force in action for yourself. (Classic Records did a few 45rpm pressings in this manner in the late 90s to early 00s). *BE FOREWARNED THAT THIS PROCEDURE COULD RESULT IN SEVERE DAMAGE TO YOUR CARTRIDGE AND WALLET IF YOU ARE NOT CAREFUL*
Turn your amplifier OFF. Re-confirm that your platter is level using a small bubble level. Initially, set your anti-skating at least mid-range in order to keep the stylus from flying too fast toward the center in this process. With the record turning no more than 33rpm, lower the stylus at the outer edge and watch it skate toward the label. Be ready to catch the arm before it gets too close to the label. Notice that the velocity slows as the stylus gets closer to the center of the record. Decrease your anti-skating a bit more and notice the difference in velocity and the change in velocity as it approaches the label.
Now disengage the anti-skating entirely and lower the stylus onto the record at a point about 1.5 inches from the label. Notice the velocity with which it approaches the label. Compare this velocity with what you see when you lower the stylus at the very outer edge of the record and watch how fast it travels the same distance of about 1.5 inches. You should notice the stylus picks up inward velocity much faster if you lower it at the outer area versus the inner area of the "playing" surface. This is happening because the skating forces are more powerful further away from the center of the record. If you don't see this in action and your anti-skating is disengaged there may be something wrong with your tonearm's horizontal bearing. Check this on a WallySkater.
Now look at your blank record in bright light and notice the micro groove you have just etched in the record surface. CLEAN YOUR STYLUS!
WHY DO WE NEED TO APPLY AN ANTI-SKATING FORCE?
Since skating forces generated on the stylus as it travels through the record groove cause it to lean hard toward the center of the recrod, without an opposing anti-skating force you will cause uneven stylus wear and premature stylus aging. Further, the increased likelihood of mis-tracking on the right groove (right channel) can result in damage to that groove during mis-tracking and the higher forces the left groove sees can cause its own wear problems.
The bottom line: We apply anti-skating to preserve the stylus and our precious record collection. Do we need a better reason than that to do it and to do it with accuracy?
HOW TO APPLY THE RIGHT AMOUNT OF ANTI-SKATING FORCE?
The perfect amount of anti-skating force varies depending upon the distance of the stylus to the center of the record, vertical tracking force, the amplitude of the music being played, the playing speed, stylus profile, the type of anti-skating mechanism being used, the alignment of the cantilever with the groove, etc. In other words, there is no PERFECT amount of anti-skating. A compromise must be struck.
By applying anti-skating as a percentage of vertical tracking force you can get to an excellent compromised "average" in your anti-skating across most of the record surface for most music at normal playing speeds.
And so, was born, the WallySkater.
The WallySkater is not only useful for measuring anti-skating - and is the only product of its type known to us - but is also very useful for learning about your tonearm's horizontal bearing quality and whether you have any unwanted horizontal forces on your tonearm applied by your tonearm wiring.
IMPORTANT: Using a blank record or the groove-less area of the inner run-out on a record to adjust anti-skating so that the tonearm remains stationary is not a recommended method to adjust anti-skating as it results in about 50% too much anti-skating force applied. A FAR WORSE method is the use of "anti-skating bias tracks" found on some test records. The high amplitude such tracks are made at will result in applying far too much anti-skating force and the premature death of your stylus and precious records. At the end of the day, the final litmus test of proper anti-skating application is to have even stylus wear over time. This is one of the reasons we inspect our stylii regularly under our modified optical microscope. The wear patterns we find confirm the science behind the WallySkater!