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I had a look at Dave's replacement 1200 bearing at the Manchester show yesterday. It certainly caught my interest and looked to be very nicely made. I see that it has been engineered to produce a very high level of drag (most successfully too) and this strikes me as a good idea and well suited to this particular turntable. If I had a 1200 I would certainly want to try this product.
That's what i have in mine ' its been nearly a month now so almost 100% run in .
There are striking difference's , even though i have the standard arm ' its easy to hear
I would say to me the most amazing improvement of all is the change in tonal balance and presentation , of course the bass is better ' improved timing and so on .
But its so much lighter tonally ' it has an open airy quality , gone is that opaque darkness which is often levelled at the stock 1200 and rightly so too .
Mark, I'm not baiting, but why all this drag? is it in the lubricant, or in the tight tolerances do you think?Quote:
Originally Posted by YNWaN
Shouldn't the bearing be free rather than tight?
I'm not an engineer but would like as simple an answer as it's possible to give..
Well Dave, It's not really for me to say as I didn't design it. However, high drag bearings have very much been in my mind these last few months so if I may hypothesise. The drag itself, I would expect, is created by a combination of tight tolerance coupled to very viscous lubrication. As you are aware the 1200 uses a feedback loop to constantly detect and correct speed errors. I have also looked into (and experimented with) feedback loops and error correction of this nature. A high drag bearing will mean that the system is unable to make very quick alterations to the system (it also means that such alterations may well be less necessary). In addition, a constant load is presented to the motor. In this situation I think it is a good idea (for what that is worth). The ear is remarkably adept at hearing very quick adjustments to pitch and timing whilst it is remarkably forgiving of longer term changes. Effectively the high drag alters the time constant of the error correction.
The bearing is free - this should not be confused with drag; it is not a high friction bearing.
Brinkmann use an interesting alternative DD solution. In their case they use a very low torque DD motor which uses relatively few poles. The platter is intended to behave as a true flywheel as the motor has insufficient torque to do anything other than input sufficient energy to overcome losses in the system (bearing friction, stylus drag).
The only problem I foresee (in an engineering sense) with high drag bearings is the requirement to ensure that drag remains absolutely consistent over a large time frame. I'm not saying this is a problem in this particular instance but it is something I have considered during my own investigations.
I can understand that ' would that explain why the new bearing gives a much greater sense of space and air around everything , although it may be a combination of the Timestep psu and bearing working together ' which is why Dave recommends getting the psu 1st .
An increased sense of 'space and air' is usually the result of reduced noise in the system and the way in which the arm, chassis, platter and record are coupled.
In a record player the noise I refer to can be very subtle indeed. Many people expect such noise to be audible with the naked ear (grinding noises from the motor for example) but I am assuming such noise is already at a very low level; even very tiny level of noise in the system corrupt the output - remember how tiny the signal produced by a low output MC cartridge is - particularly at high frequencies where many of the auditory cues that suggest 'space and air' exist.
So the feedback loop error correction is doing a lot less work and we have much lower noise and friction in the bearing ' these are the two main advantages over the original bearing and indeed psu .
Thank you Mark...
Obviously this wouldn't work in my SL150 and Dual 701, as the motors don't have much if any over-torque in either deck. To be fair, neither of these "hunt" either - if they're given drag they just slow a tiny bit and then return to nominal...
Perhaps Mike or Dave Cawley could post a reason for this design? Like you, from afar I'd suggest a viscous lubrication rather than a high friction bearing...:)
No problem, happy to help. However, this is only my interpretation of the situation - the actual designer may feel differently.Quote:
Originally Posted by DSJR
I couldn't comment directly as I am insufficiently informed with regard to those decks. What I would say is that there should be sufficient rotational potential in the system (be that from the motor or from a rotating mass) to overcome any drag that the system may encounter. Observing how the platter behaves when a finger is applied tells you something about the absolute torque of the motor but very little with regard to how the system actually behaves when playing a record.Quote:
Originally Posted by DSJR
I'm not so sure that feedback loop is actualy doing less work (it may be but I would have to look at the system more closely) - however, it is likely that the work it is doing impacts upon the system in a quite different manner.Quote:
Originally Posted by chris@panteg
JC Verdier has enthused about the idea of a high drag bearing for a good number of years, feeling that it allows a degree of constancy & control to the rotation.
there is a piece about it somewhere on t' interweb.