Direct Drive

Laugh all you like but a Vestax and Numark DJ deck are both very effective 

@pedroeb

My turntable is built around a New Way thrust bearing, an air bearing in all three dimensions. This right away puts you in rarified (6 figure) company.

Next is inspiration from the late Tom Fletcher, who reasoned that a tiny motor couldn’t do much to influence a large rotating mass. I use a Premotec 1.8W precision synchronous motor, which does not catch up using feedback, but instead produces a constant rotational speed. Of course, with this setup, you have to bring the platter up to speed by hand, which is a bit quirky, but not at all inconvenient.

Motor resides on its own massive board made of Panzerholz, a wonderfully dead and dense and strong plywood from Germany, which is isolated from the main chassis and the platter.

Motor controller can be as simple as a capacitor or two, or you can build one with (electric) quadrature, which is better. Maybe better left as a project to get around to someday.

Platter is cast iron base covered with a 1" graphite top, both located precisely on an air bearing spindle. (Inspiration Tom Fletcher again) While each rings a little when separated, the assembly is dead as a tomb. If I were doing it again, I would bite the bullet and get New Way to machine the spindle.

Suspension is something which I did not need, so I did not build, because my listening room has a concrete floor built on bedrock, and miles from a highway.

Air supply depends on your situation. If you use an oil-free compressor you don’t need to do much in the way of filtration, but if you need to use oil (quieter, cheaper) you need to go with heroical air filtration to protect that $1K thrust bearing.

There you have the basics. Let us know how you get along! Good luck!

PS: There is a thread on DIY Audio about this. Very long, very detailed.

How does it sound? Well, I can HEAR the noise from the plastic sleeve bearings on that 1/500 HP motor! Only faintly audible as a slight grainy brightness, but audible nevertheless.

Paired with my DIY air bearing tonearm and higher end Koetsu (diamond), it’s a pretty stunning combination. Makes my Nottingham Analogue Mentor upgraded to Dais standard (Fletcher again!) sound highly coloured and even a bit nasty by comparison. And the stock Mentor was a DD killer, IMO.

Oh - and use a short belt.

I have to take issue with Bliss, who wrote, "There are some incredible direct drives, but their notoriety was largely due to motor noise and vibration."  I don't mean to pick on Bliss, but his statement is often the mantra for those who don't care for DD turntables.  It's just plain wrong. There is no mechanical noise or vibration added by virtue of the DD technology.  In DD turntables, the platter either is the rotor or is firmly attached to the rotor of the drive motor.  The drive force is electromagnetic between the rotor and the stator.  Nothing touches the spindle or the bearing or the platter that does not also touch the spindle/bearing/platter of any other type of turntable.  What CAN be an issue with DD turntables is EMI or electrical noise generated due to radiation from the motor.  In 99% of decent DD turntables, EMI is shielded from the cartridge by the platter itself, which is usually made of stainless steel or aluminum or some alloy of copper. In fact, of course, both BD and idler type turntables have a greater potential to transmit mechanical noise from the motor to the bearing or platter, because both require a mechanical interface between the platter and the driver.

Dover, With respect I must also disagree with your persisting claim that the servo systems of "vintage" DD turntables, designed usually in the late 70s or early 80s are so primitive as to cause audible`distortions due to speed corrections mandated by those circuits.  First, most modern BD turntables wouldn't be caught dead without a motor controller of some sort, with or without feedback, to maintain constant speed.  And I for one have consistently heard the benefit of those devices if designed well, on the performance of one or another BD turntable.  Second, a skilled engineer, JP Jones, has graphed the speed stability of a brand new Technics SP10R, which I think we can agree would incorporate the most modern devices and moreover uses a coreless motor, vs a fully tweaked SP10 Mk3.  JP found no detectable difference in the speed constancy of these two turntables when he monitored them over time in a way that would reveal momentary peaks and troughs in speed, if such were present in the Mk3.

I am not saying anything is perfect, and I certainly have heard BD and idler turntables that I much admire, but if you categorically dislike DD turntables, find other reasons.  Most likely, it's EMI, in which case that reflects poor design or construction of the platter.

@lewm 

I don't doubt that the average speed of a modern turntable is right on the money. But, according to accepted statistical theory, there is more to a phenomenon than just the mean.

Consider the platter speed to be a random variable whose distribution of values is some distribution D. Since a normal or Gaussian distribution is completely determined by two parameters, mean and standard deviation, if D ~ N(m,s) the situation is more complex than the mean. In general, the utility of mean as a unique determinant of a quantity is obvious when you consider wealth, like B Gates and one of us, etc. etc.

And a normal distribution is very well behaved at two parameters. Most distributions are described by more. These are the higher level moments, standard deviation (actually its square, the Variance; second), skewness (third), kurtosis (fourth), and the rest of the infinity of central moments have no common name. It is a theorem that any distribution can be uniquely described by its moments.

What this is all getting to, is that the higher order moments of the speed distribution are all noise, noise which is not much considered and not much measured. Our ears measure it though - it comes through as an almost sibilant brightness, a nasty sound. The best DD don't have much of this, but the big new Technics with its associated system seemed to produce way too much of that for me, when I heard a factory audition.

And what can we measure? Mean speed over a window of some duration.

To measure these higher order moments requires very many, very short window measures of mean speed, and applying the correct estimation algorithms. Shorter is better, and 14 bit resolution should be the absolute minimum. The fact that 'speed stability' is reported while standard deviation, skewness, and kurtosis is not, is revealing. It seems to be a matter of the engineering not keeping pace with either theory or perception, IMO.

What do you think?

@pedroeb  Make that the Premotec 9904 111 31813 (as it was then designated), then available from Element 14, IIRC.