Direct drive/rim drive/idler drive vs. belt drive?

T-Bone

Maybe you have me confused with someone else.

I have never advocated the use of any form of slip in a turntable transmission. I understand the theory of it being used in an attempt to reduce cogging but I think it's the kind of half baked idea propounded by people who really don't understand the mechanics of TTs. You will have noticed that there are a lot of them about.

I have pointed out many timnes that belt creep (and idler creep) is an inevitable consequence of using compliant coupling materials but that could not be construed as advocating its deliberate introduction.

Mark Kelly

Mark,

I have not mistaken you for someone else. I am aware of your issues with belt creep. In fact, because I was trying to dance the long way around a subject which I think may be of commercial importance to you, I ended up mis-communicating. Please ignore my comment.

Play on ladies and gents...

"I understand the theory of it (belt creep) being used in an attempt to reduce cogging but I think it's the kind of half baked idea propounded by people who really don't understand the mechanics of TTs." - Mark Kelly

I cannot agree more. Well said!

Once again, if a turntable needs a soft rubber belt to reduce coggging or noise from the motor in order to sound competent. Get a different motor or change to a different drive system. It's just that simple to me. Some think platter or bearing is more important because motors don't get the blink blink like a thick shiny platter and they are always tuck away in the back or hidden and do not get the attention they deserve.

Mark: I am no expert but my experience is that the heavier the platter on the belt drive T/T the more likely we are to have less variations in speed. I owned a Michell Gyrodek for some years and always knew that its speed stability was marginal. It wasn't until I purcahsed my present Acoustic Signature Analogue One Mk 111 that I realized how bad the Gyro had been. I know that things are relative. I have to assume that both decks are well engineered within the requirements of each design. I am inclined to believe that the real reason that the AS is better is because the platter has higher mass. I am not aware of how heavy the platters are on idler T/T's but would make an educated guess that they are much less than the AS which I will use as my reference.

In the case of the idler T/T at no point is the platter allowed to rotate in a 'free' state. The idler drive is always in contact and driving, even if we admit that there IS some compliance in the rubber driving material.

I stand by my firtst statement that the two systems are completely different and both can work or fail. It's really only about engineering.

Clarkie

Hiho,
well, well, well.

What you seem to overlook is the reality of it all. Just have a look at HOW MANY tt manufacturers use exactly that 'rubbished' approach and then ask yourself why.

I think a STABLE AC motor (not DC which is prone to drifting) is just cogging, some more, some less, even 3 phase, and so along comes the soft, long, or what ever, belt to 'fix' it. At the same time mass is added, has to be added to the platter, to counter act the soft belt drives lacking dynamic performance.
Practically ALL tt's that make the top grades (Hi-End rating > 100 points) in all known to me German Audio Magazines are designed that way.
Then a 'controller' may be added (in some cases more of the name then the real thing), at extra expense.

The question: how much does one actually hear the difference?
Point to add: it was one of these 're-worked' Garrarde's (by Loricaft) the wound up pretty much on top of the heap. It was superior DYNAMIC performance that did it to the testers... alas not the high price with some questionable suspension on squash-ball, and other sundry items.
Greetings,