Please follow me on a journey that explains the relevance of good TT and DD motor technology. Imagine if you will, there are 3 automobile drivers. All 3 drivers will drive through the most beautiful parts of the Swiss Alps, or the Smokey Mountains, or any other beautiful and breathtaking scene. Driver one is performance oriented and cares most about how his car will handle through this beautiful and challenging terrain. Driver 2 cares more about how beautiful the scenery is going to be. Driver 3 cares equally about the scenery and the drive, and expects quality from both. I fit well as driver 3. I want the quality of the drive to be so good that it virtually disappears so I can concentrate on and value the beauty of the landscape. The speed limit on this road is, for exaggerating purposes, 33.33 miles per hour. All 3 drivers first get to drive a car with a cruise control spec of 33.33 +/- 0.002 miles per hour. This car has a disc attached to one wheel with 4700 lines on it. A sensor reads these 4700 lines throughout every tire revolution to produce the advertised spec.
Driver 1 is so impressed by the technology and performance of the vehicle and finds it exhilarating. Driver 2 really has no opinion and is very happy to be an active participant. Driver 3 is very unhappy. He is experiencing a constant micro struggle of power from within the car; with its constant applying of power and brake, he feels the jitter in the car, its annoying, and therefore distracting him from enjoying the breathtaking scenery.
The drivers are now given a car that has a different technology. It only monitors speed once every wheel revolution to maintain speed. The sensor is mounted on the outer most part of the wheel for accuracy. The spec is 33.33 +/- 0.1 miles per hour. Driver 1 is very unhappy. He immediately notices less speed control on sharp turns, up, and down hills. Driver 2 is just happy to be there. Driver 3 is happier than before. For him, the drive is smoother and its letting him enjoy more of the picturesque landscape, but feels more like a roller coaster at times.
The drivers are lastly given a car with technology that measures engine load only. Its job is to keep the speed of the engine at a constant regardless of load. The cars computer was programmed to specific values that would maintain a speed of 33.33 miles per hour on a perfectly flat and level road. Having no sensors on the wheels, the engine has no idea what the wheels are doing, or how fast they are spinning.
Driver 1 is very unhappy. It seems the engine has no idea what its doing. Its all over the place. The engine performs great on a flat open road where there is no load, but in the mountains, it struggles. Driver 1 at times feels that the speed just isnt correct. Driver 2 is just happy to be there. Driver 3 is miserable. As hes trying to enjoy the beautiful views, the images at times are blurry. As he passes trees, sometimes it looks like one big blob of trees, and at other times, he can pinpoint how many trees there are. Hes having trouble focusing on the picturesque landscape. He concludes that the speed of the car is deviating so much that its distorting the view.
The diamond tip on the stylus is the passenger in the car driving through the beautiful terrain and experiencing the landscape of the vinyl. The TT is the cars motor. Car 1 suffers from extreme micro management. Its constant control of the motor fights with the natural forces of the landscape. This motor will suffer from what I call negative speed. Simply, the stylus wants to behave in a natural forward moving manner. A stylus traveling down hill does not want to brake several times, just as when it wants to travel up hill, it doesnt want to brake several times. The stylus in this case, for an almost immeasurable instant, travels backwards on the vinyl. Some may call it cogging, some may call it pole jerking. This negative speed is actually a form of recoil. Many people will use words like lifeless, boring, unrealistic, smeared, dry, bass shy, and bright. The constant internal power struggle to keep the motor at a strict speed ruins the landscape for the stylus. The music never blooms and is stripped of its magic due to the motor electronics being a control freak. Specs are great though.
Car 3 allows the stylus a little more freedom to travel, however too much. The problem is that at times, the motor is pushing the stylus down the hill when it shouldnt, and at other times holding it back. The motor really has no idea whats going on at the road surface. Its job is to just hold the speed as steady as it can via a current feedback circuit. If more current is detected due to a load increase, more voltage is applied to the motor. This system also suffers from motor recoil, but on a smaller scale. The difference in this case is that the platter is being belt driven. The elasticity in the belt will absorb some of this, but the downfall is that there is then the recoil of energy caused by the belt itself. In the end, the stylus is really forced into situations of being out of control. Its sort of bob sledding. Some will describe the sound as bouncy, jumpy, lively, boomy, smeared, and unfocused. In poorly designed belt drive system, you can also have the symptom of negative speed due to the microscopic rocking of the platter forth and aft.
Car 2 is the better of the 3 cars, but certainly not perfect. The motor will hold its speed for the one full revolution, take a reading, make any adjustment if necessary, and wait for the next reading 1 revolution away. The one revolution allows the stylus to glide more naturally. In other words, when the stylus is going down hill, its not being pushed, nor is it being pulled back, or forced to brake. It can travel at a velocity more natural to the landscape of the groove. It will tend to micro speed-up by itself, naturally. When traveling up hill, the stylus will micro slow-down, naturally. One may ask, well how can that happen if the platter is ideally at a constant speed for at least one revolution at a time. Isnt there a contradiction? The answer is no. Without constantly micro managing the speed, the stylus and its suspension are allowed the opportunity to function properly. The cantilever will bow positively going down hill, and negatively up hill. The suspension of the cantilever is the shock absorber. The more rigid the cantilever (like beryllium), the less positive and negative bowing will occur. The problem now becomes that the quality of the sound deteriorates as the stylus moves towards the center of the vinyl record. Placement of the sensor is critical. Placing it at the outer most edge of the platter will yield less frequent speed correction per distance of stylus travel, and too much speed correction at the inner tracks. The only way to try and compensate for this would be to monitor the location of the tonearm on the record. For instance, if the tonarm is in the middle of the record, it skips a reading, and checks speed every 2 revolutions. Unfortunately this just isnt workable. A TT like this can sound lively and natural, but not for the entire record.
The best DD motor would be one that is able to maintain constant speed, without any external feedback systems, accept a reasonable load, and not compensate for speed. The magnetic motor is really the only viable solution. Too many manufacturers decide on specs first, and sound later, then slap a few band-aids on at the end. A magnetic drive motor that is manufactured properly will yield the best results regardless of where the stylus is on the record. No amount of electronics can ever compensate for a badly designed or cheap motor. You can have 10 speed boxes connected and it wont matter. In the self contained system of magnet drive, it only has to worry about maintaining the correct magnetic field. In theory, if the magnetic field is correct and constant, the speed will be correct. Any corrections made would be extremely soft and undetectable corrections, as the change is not direct and done through a magnetic field to micro manipulate the motion of magnets. This is where I believe the true magic in the sound of vinyl exists. We can control VTA and VTF, and yield amazing results when hitting the sweet spot. But unfortunately, we cannot control a miserable and faulty designed drive system. If the stylus and its suspension are allowed the privilege of un-interruption by giving it the opportunity to glide at a true steady speed in its natural state, that my friends is the icing on the cake. Like vacuum tubes are soft switchers, solid state are hard switchers. The ideal DD motor will make the TT disappear, and let you forget that youre listening to vinyl, draw you in, and allow you the privilege of participating in the soul of the music. The most important part of the drive system besides being quiet, is to allow the stylus to be itself, only then it becomes transparent, and presents the magic within the vinyl.
Best Regards
