Once Analog Posted March 25, 2014 Share Posted March 25, 2014 (edited) That's a simple question but the answer can be very elusive. Curiously, if there is an answer at all, it is probably that there is more than one answer. But is it possible to have more than one best? No! So what's the story? Take a look at the abbreviated list of electric motor types shown below. Some of these are commonly used in turntables, others are rarely used and a few are non-contenders. Drive technologies have evolved along with the historical development of motors and this has led to some older motor types being adopted for new applications. There are many schools of thought (philosophies) that motivate turntable designers to focus on a particular concept, parameter specification or technology. However there is no ideal solution. During development, choices need to be made that often result in a compromise. It may not be possible to please all audiophiles all of the time but creative designers can certainly find a niche group that they can satisfy, even to the extent of conversion to fervent followers. Classification of Electric Motors AC Motor Types Induction Motor Polyphase cage rotor Polyphase wound rotor Two-phase servo motor Single-phase induction motor Shaded-pole motor Split-phase motor Capacitor start motor Synchronous Motor Polyphase synchronous motor Single-phase synchronous motor Hysteresis synchronous motor Permanent magnet synchronous motor (clock/timing motor) Other AC Motors Universal and series wound motor Repulsion motor Exterior rotor motor Sliding rotor motor Electronically commutated motor (brushless DC motor) Watt-hour-meter motor DC Motor Types Brushed Motor Internal commutation Permanent magnet stator motor Slotless permanent magnet motor Brushless Motor Electronically commutated motor (synchronous AC motor) Switched reluctance stepper motor Synchronous reluctance motor Variable reluctance stepper motor Uncommutated Motor Homopolar motor Ball bearing motor Wound Stator Motor Series connection Shunt connection Compound connection OA Edited March 26, 2014 by Once Analog Link to comment Share on other sites More sharing options...
soundfan Posted March 25, 2014 Share Posted March 25, 2014 Probably not best, but the motors in the Lenco GL75 just keep on keeping on. Brilliantly reliable IMO. Link to comment Share on other sites More sharing options...
Anthony John Colbert Posted March 25, 2014 Share Posted March 25, 2014 how long is a piece of string lol. From what i can gather, in the simplest form, AC motors are easier to get speed accuracy with, and generally have more torque but they vibrate and cog. DC motors dont cog and vibrate a lot less, but generally have less torque and can be more difficult to maintain speed accuracy with, in that the voltage not the mains frequency controls the speed. 1 Link to comment Share on other sites More sharing options...
Gruffnutz Posted March 25, 2014 Share Posted March 25, 2014 The best turntable motor is the one you don't notice. 2 Link to comment Share on other sites More sharing options...
LogicprObe Posted March 25, 2014 Share Posted March 25, 2014 Can of worms! Link to comment Share on other sites More sharing options...
andyr Posted March 25, 2014 Share Posted March 25, 2014 The best turntable motor is the one you don't notice. WOW ... what an absolutely zen koan, GN! I don't actually "notice" either of the 2 AC motors I can use on my TT - so which one is the better? (Hint; maybe you actually have to listen to the result which the motor - and, of course, its power supply - deliver! I'm talking about drive, bass, soundstage ... etc.) regards, Andy Link to comment Share on other sites More sharing options...
Number 9 Posted March 25, 2014 Share Posted March 25, 2014 (edited) As you will probably know by now, I've spent the last 18 months designing myself a turntable. Very early on in the piece I had to choose what sort motor I would use. The choice was whether to go with the DC motor, your Maxims and the like, which had become the latest design trend among turntable designers or to stick with the Premotec AC motor I knew from many years selling turntables. The Premotec motor has been out there, functioning reliably for over 40 years. As to the DC motors currently in vogue, in terms of realiability, ask me again in 30 years. In terms of speed accuracy, the Premotec motors are ridiculously good, provided they are driven with a precisely controlled frequency. Using an appropriately accurate control device, the Premotec motor is capable of accuracy to within 0.2 cents (two thousandths of a semitone) at 1 kHz using a bog standard 50 ppm crystal. A classically trained professional musician can generally tune his instrument to within two cents. These are real world figures based on my setting up of Andy's Skeletal whatever last Sunday afternoon. The new version of the controller will use a 2.5 ppm crystal and should theoretically at least, achieve accuracies of the order of 0.004 cents. As to the issues of cogging and vibration, careful manipulation of the phase angle between the two windings of the Premotec motor will virtually eliminate this problem. All this, plus an almost guaranteed service life of 30+ years, is kind of hard to pass up. Steve. Edited March 25, 2014 by Number 9 Link to comment Share on other sites More sharing options...
Once Analog Posted March 26, 2014 Author Share Posted March 26, 2014 Probably not best, but the motors in the Lenco GL75 just keep on keeping on. Brilliantly reliable IMO. Hi Soundfan, Agree, the L75 is a great turntable and the motor is as you say, very reliable and quiet running. Wasn't the conical motor shaft clever and not to mention the vertical Idler wheel, no side way force! OA 1 Link to comment Share on other sites More sharing options...
Once Analog Posted March 26, 2014 Author Share Posted March 26, 2014 Motor Selection Criteria The selection of a motor type is not trivial. Making a choice is unavoidably influenced by many factors some of which can be quite perplexing. The situation is similar to attempting to solve a complex mathematical equation where all the variables and constants keep changing roles. Regardless of the engineering knowledge, creativity and technical ability of design individuals or teams, a product is inextricably associated with the principle of enterprise. It is a cold fact that a business needs to be profitable but that doesn’t necessarily mean the development process is devoid of soul. In fact, with the addition of feedback, the equation begins to acquire characteristics of a living organism. OA Link to comment Share on other sites More sharing options...
Stump Posted March 26, 2014 Share Posted March 26, 2014 The Clearaudio Innovation use a high torque DC-motor with optical speed control.Together with a Clearaudio Accu Drive its quiet but with your ear up against it you can still hear it.! But not from the listening chair Stump Link to comment Share on other sites More sharing options...
Stump Posted March 26, 2014 Share Posted March 26, 2014 If you went with the krispy special it looks like a good deal.I have had the Clearaudio Performance and are a well built German machine. Stump Link to comment Share on other sites More sharing options...
Once Analog Posted March 27, 2014 Author Share Posted March 27, 2014 (edited) As you will probably know by now, I've spent the last 18 months designing myself a turntable. Very early on in the piece I had to choose what sort motor I would use. The choice was whether to go with the DC motor, your Maxims and the like, which had become the latest design trend among turntable designers or to stick with the Premotec AC motor I knew from many years selling turntables. The Premotec motor has been out there, functioning reliably for over 40 years. As to the DC motors currently in vogue, in terms of realiability, ask me again in 30 years. In terms of speed accuracy, the Premotec motors are ridiculously good, provided they are driven with a precisely controlled frequency. Using an appropriately accurate control device, the Premotec motor is capable of accuracy to within 0.2 cents (two thousandths of a semitone) at 1 kHz using a bog standard 50 ppm crystal. A classically trained professional musician can generally tune his instrument to within two cents. These are real world figures based on my setting up of Andy's Skeletal whatever last Sunday afternoon. The new version of the controller will use a 2.5 ppm crystal and should theoretically at least, achieve accuracies of the order of 0.004 cents. As to the issues of cogging and vibration, careful manipulation of the phase angle between the two windings of the Premotec motor will virtually eliminate this problem. All this, plus an almost guaranteed service life of 30+ years, is kind of hard to pass up. Steve. Hi Number 9,Thank you for posting in my thread, enjoyable reading. Please keep us informed with your turntable building. With regards to "Premotec", they make a couple of DC motors that are excellent for turntables; CL29 and CL40, both available in 3 Watt/12 Volt. The CL29 was used by OL, the CL40 currently used by "Michell". OA Edited March 27, 2014 by Once Analog Link to comment Share on other sites More sharing options...
Once Analog Posted March 30, 2014 Author Share Posted March 30, 2014 (edited) Best Turntable Motor"Choosing The "right" Motor: A Scenario" A small, possibly fictitious company named BTEC – "Best Turntable Ever Created", is developing their inaugural model. Sue is the owner-manager, marketing, logistics and finance officer. John is the engineer who performs the remaining functions for the company.For the last three months Sue and John have been busily engaged researching the new product. The weekly meetings have been exciting and productive. They have already decided that the showcase model, BTEC-1, will be an audiophile turntable. It will have a solid wooden plinth, an exquisite piano black finish and a custom cut-out section to accommodate a selection of premium, industry standard tonearms.Considerable time and effort is currently being expended discussing candidates for the platter and drive system. John is inclined towards a high tech approach but Sue knows that true audiophiles would prefer a minimalist system that conforms to the KISS rule.Eventually they elect to proceed with a high mass platter and belt driven. Now the only key component requiring debate is the motor. Sue asks John; "Which is the best turntable motor"?John sighs, turns his notebook towards Sue and reveals over two hundred pages of engineering data, reviews, articles, internet forum threads and other musings he has collected on the subject. Sue, now savvy to the complexities of the issue, remarks "Well, at least our decision to use belt driven, has reduced the spectrum of choice for the motor"!Fast forward six months. The pre-production prototype has been undergoing testing for a feature article in a respected audio journal. The experienced reviewer, Peter, is meeting with John and Sue to discuss his findings and investigate the design philosophy supporting the BTEC-1.It seems that Peter is impressed by the appearance and overall performance of the turntable but has a question about the motor. "Why did you use an AC induction motor", he asks? While Sue is explaining that the BTEC-1 was targeted at purist audiophiles!John examines the test results. He knows that despite the AC motor’s characteristic 2% magnetic slip, inelegant manual speed change and risk of mains interference they had to trade off these concessions for the sake of a timely production release.John boasts "Our minimalist BTEC-1 model will soon be followed by the new BTEC-2 featuring a technologically advanced DC motor and external controller."Encouraged by the discussion, Peter is intrigued by the potential of future BTEC developments and begins to wonder about which DC motor type is best.The journal publishes Peter’s extravagantly enthusiastic review.Conclusion Although the example scenario may not accurately represent the real world, the problem with the original question is real and persists."The best choice of motor for any turntable system is the best motor for that particular application". You were probably hoping for a more satisfying outcome, but this conclusion truly is the best I am willing to offer.Enjoy the music,OA Edited March 31, 2014 by Once Analog 1 Link to comment Share on other sites More sharing options...
Guest Posted July 25 Share Posted July 25 What's today's take on turntable motors? Any progress made since this thread within the hobbyist circles? PS ... Google pointed me to this thread when I asked the question Link to comment Share on other sites More sharing options...
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