Hello Dertonarm,
>The "air-pulse" drive (no pulse would exclude a problem) has some considerable problems while looking close to a theoretical ideal first. It not only will require considerably (really serious...) periphery, but indeed a "assist"-motor to bring the (high mass) platter to requested speed first and than de-coupling.<
Weren't you asking about "all out",no compromise, no commercial consideration approaches? Did I not explain some of the caveats? Yes, the periphery would be expensive, but maybe not as expensive as it appears(remember, this is not about a commercially viable project).
The Onkyo PX-100M eddy current drive turntable does feature an idler drive just to bring it up to speed within half a revolution, then the eddy current drive takes over(and it has a break too). It can be done...
Platter speed needs to be monitored, which in turn can govern the force of the air(or any other driving) "pulse". It will have a VERY slow recovery time, but(that is where my chronometer analogy comes in) the disturbing influence of the drive system could be minimized.
To assess which principle is superior, we'd have to build two(or more) otherwise identical turntables that can be driven by more than one means. I have done this several times many years ago, Chris Brady has done this more recently, so his assesment holds merit, even if some may not agree with all of his peripheral design choices.
I suggest opening another thread to discuss that there is VASTLY more to building an excellent turntable then the drive principle, even though nothing else matters if the record doesn't spin at (as close to)constant speed to begin with.
Dertonarm, I didn't ask you any questions, I just showed that your approach is just as far from or as close to being perfect as some other approaches, at least from a conceptual/theoretical point of view. But that part of the discussion was doomed from the start... and yes, it's not neccessary to repeat yourself yet again.
Nevertheless, have an enjoyable and relaxing Easter weekend!
Frank
