Lewm, I did not mean to imply DD to be better, but equal in sound Performance characteristics w/ CMB, the latter having less-er friction. To tell you the truth I have both mechanical and CMB version and prefer the original mechanical bearing the best. It is not, i think, the magnetic bearing feature (which is horizontal BTW, the ceramic being the main spindle) but the ceramic spindle that hurts the overall performance. They have not optimized the stiffness spindle, me thinks and hence less stiff than the mechanical bearing metal ( steel)spindle. |
Hiho
When I said "about the lowest creep of any system outside DD" I was thinking that the drive I designed for Thom Mackris was probably slightly lower. I was wrong.
I've run the numbers, assuming you are running a 1/2" x 3mil Mylar belt around two 300mm platters placed 400mm apart, and you win. We have slightly lower compliance (0.063 mm/N vs 0.117 mm/N) but you have a longer effective pulley length (236 mm vs 68 mm) so your creep is lower: 0.003 vs our 0.005, referred to a radius of 150mm.
As a reference, a typical belt drive system might have a creep number around 5 - 10 and a good idler system (like Win's) will have a number around 0.05, over 100 times better than the belt drive.
Mark Kelly
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Nilthepill, I guess I don't understand the concept of the CMB. I made certain assumptions that must be off base. I've actually never seen any Clearaudio turntable, except perhaps their low end ones, in the flesh. But then, I lead a sheltered life here in the Washington DC area, where the hi-end audio emporium is as rare as a dinosaur. |
Lewm,
that 'Clear Audio' magnet repulsion is comprised of two ring-magnets ~ 2 1/2" outer diameter and ~ 1/4" in of magnet width. They then replaced the centre bearing pin with a ceramic pin (as you noted, I think). All it now does is not sit on a tungsten ball down the bearing well, but ALMOST float - presto.
This system is pretty much the same thing also use with the 'Pro-Ject 10' and some others like Transrotor that sells it as an upgrade purchase for e.g. the Fat Bob and Z3 etc.
This is in COMPETE contradiction to the 'Platine Verdier' tt which on purpose applies a constant bearing friction-load to stabilise their high-mass platter.
From experience I can tell, that the SME motor/controller is loop-locked much quicker when a small degree of friction is present. In fact if the controller is still trying to lock (can see on the controller's light indicator) and you only put the stylus in the start groove - voila, it's locked!
The looser the bearing the longer it takes the controller to lock (SME main-bearings are conical and can be adjusted for more or less friction)
Go figure...
Axel |
Axel, This is like the eddy current brake on a Garrard. Mark Kelly has written much on this subject. I now get what you and Nilthepill are talking about; the repelling magnets not only provide a force in the vertical plane but also they resist rotation in the horizontal plane due to the eddy current effect. Cool. I neglected that factor in my earlier post. |
"This is in COMPETE contradiction to the 'Platine Verdier' tt which on purpose applies a constant bearing friction-load to stabilise their high-mass platter."
By my way of thinking, the Verdier approach is far more elegant. The bearing friction load, if that is what to call it, combined with compulsive obsessive tight tolerances can act in a way similar to a grease bearing by also creating a dynamic brake of sorts. The beauty here is that it doesn't have obstacles, like misaligned magnets to deal with, or any influences that might be caused by them. It's a case of less is more in that less complexity is involved to achieve a result that may in fact be superior. It also indicates to me that the manufacturer has taken more care in a traditional approach, if his result is an extremely good one.
A manufacturer can use tricks like magnets as a workaround for the unwillingness to spend extra for precision machining or better materials. I'm not saying that any particular company is doing that, but I do see the possibility.
Summary: I don't buy into magnetic levitation for platters.
Win
Saskia Turntables |
Lewm
There is effectively no damping effect available from the two opposed magnets. Eddy currents are proportional to field strength times relative velocity divided by electrical resistivity. The configuration used results in low relative velocity. The electrical conductivity of available magnetic materials is quite high - NdFeB magnets have about 100 times the resistivity of copper.
For all: A distinction needs to be made between velocity dependent drag, which will tend to stabilise the system against speed variation and classical friction (velocity independent) which will not. Hydrodynamic drag and eddy current effects are in the former camp, standard bearing friction and stylus drag are in the latter.
Mark Kelly
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Lewm
what Quiddity is relating, as I seem to understand it, is that eddy current 'friction' is very much on the minimal side with the magnetic repulsion, almost levitation, ring magnet concepts. Also recall those magnets are only about 1/4" wide rings. To support this, it is told, that if these platter are (disconnected from the drive) pushed by hand seem to run 'forever' and thereby VERY MUCH differently behaving the 'Platine Verdier' mentioned by example.
Now go figure yet some more ... :-)
Axel
PS: a difference in VFT of .75g, now I'm running at 0.75g with an Empire S1000ZE/X (0.25g! - 1.25g spec) as compared to 1.5g spec. for a 'M20FL super' give the my controller a lot more 'pain in the a...' - it take just longer to settle. This is for me a clear indication about what friction (needle and/or bearing) does in terms of motor/controller loop-feedback/response... |
Mark, Thank you for putting us back on the right track, as you always do. I had read somewhere else that the Verdier develops an eddy current effect by virtue of its apposed magnets, so I assumed that the same might be true of the Clearaudio. Are your remarks re the effect of bearing friction in agreement with Win's description of the virtues of the Verdier? |
Lew,
Maybe I spoke out of school because I believe I am the one who may have confused the issue. Unlike either Clearaudio or Verdier, my turntable uses an eddy current motor. At least, I believe neither of them uses one. Anyway, I also am a believer in the use of hydrodynamic drag, as Mark calls it, so any reference to friction drag was maybe the source of confusion.
Win
Saskia Turntables |
As one who has just wasted the better part of a beautiful hot Sunday afternoon trying to assemble my Lenco in its slate plinth, only to fatally smudge the professional paint job on the PTP3 (it will need to be redone) and find that I had ordered the wrong very fancy push-button switch, I am in no position to take issue with anyone else's feaux pas. Who knew that "off-(on)" in the Mouser catalogue is not the same as "off-on"? I now know. This is not really OT because I am talking about assembling an idler drive tt. |
Lewm
Win correctly described the influence of the Verdier's deliberate use of a trapped layer of lubricant to contribute hydrodynamic drag which lowers the Q of the platter / belt system.
That he did not use exactly those terms is neither here nor there - I have chosen my words to highlight the difference between two types of resistance which are usually lumped together as "friction".
Mark Kelly
BTW (on) usually means momentary.
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Mark,
I believe Lew figured out (on). Now, he has the only Lenco that truly works only on demand. ;)
Thanks for saying what I meant regarding hydrodynamic drag. What I was eluding to is the constant war of trendy vs. innovative. It is easy to write copy that promotes a design, but it isn't so easy to create a design that stands on its own. That is what audiophiles should really look for in products, but it is hard sometimes when ad copy clouds the issue.
Win
Saskia Turntables |
Thanks, guys, for putting me on the right track as to the theory of the Verdier and the harsh reality of pushbutton switches. Sadly, I now see that pushbutton switches of the "push-on/push-off" variety are rare indeed, and I need to find one to fit the 5/8" hole that I already drilled to accommodate it. As Win and I discussed, the switch I did buy will work fine, IF I want to stand by the turntable with my finger on it whilst I listen to music. It does, however, fit the hole I drilled. Live and learn. |
Lewm,
How entertaining... a turntable with a deadman switch...
:^) |
Lew, See Allied Electronics p1069-1099 for many types with illustrations. |
Lewm,
I know it's more PT to wire it up, but most of these switches work with a relay. Press once it comes in (switches on), press again it trips (switches off) :-)
Have fun, |
Lew, I would look into the switches used on guitar stomp pedals, see: http://tubesandmore.com/
click on 'Switches & Footswitchboxes', then P-H493 |
Axel, You mean the "momentary" switch like the one I tried to use can also be used with a relay? That's an interesting point. There's no place to hide the relay in a solid slate plinth, but perhaps a small one mounted underneath would be unobtrusive enough to get by.
Ralph, those guitar switches are pretty big, are they not? Has to fit a 5/8'-diameter hole, but I will look at your referenced site.
Dave, I think I looked at the Allied catalog at about 2 AM last night. In my groggy state, I may have missed something. I did find a near-to-correct size switch made by APEM, sold by Digikey. I think I can fudge it with some washers.
Sorry, this is so-o-o-o off-topic. But it is my very preliminary observation that a massive plinth (layered wood or slate) makes good direct-drive and idler-drive turntables sound not only better but more alike than different from each other. I am pursuing this comparison further. It keeps me off the street, most of the time. |
Lew, 5/8" is a pretty big hole. The stomp switches are usually set up for 1/2".
We found that the plinth had a lot of effect too- again, it is a resonant signature, and one unique to each 'table. The more you can reduce this issue (along with tighter coupling between the platter bearing and the tonearm) the less signature the individual machine will display: bass will have more impact, overall greater dynamic impact (more lively, without added brightness), blacker backgrounds... again a lot of the same effects that deadening the platter has. |
Ralph, I agree completely with what you say re the effect of plinth-ing. I was surprised that the slate plinth had such a profound effect on the "sound" of my Denon DP80. I would have thought that a direct-drive system would be rather a closed one in which colorations introduced by the drive were directly "injected" (for want of a better term) into the audio signal via the coupling of motor to spindle. Thus, except for better controlling the inertia of the motor itself, I thought that the positive effect of the slate would be limited. I was quite wrong.
"bass will have more impact, overall greater dynamic impact (more lively, without added brightness), blacker backgrounds..." That's what I hear too. Win's turntable (the Saskia) must be quite awesome. |
Lewm
The easiest solution I can see to your problem is to have the switch control a relay. If you have lowish DC voltages available (preferably either 5V or 12V) this is easy to do.
You'll need some logic to convert the momentary action to a latching action but it's not hard to do. Since I have B+ delay on all my valve gear I use mains switching by relay as a matter of course anyway and I like the safety aspects.
Mark Kelly
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Thanks for the help, Mark. I actually found a plain old push-push switch that will likely do the job, but the relay is my next option. This is just to switch a Lenco motor on and off, so sophistication is not a priority. |
Ralph: brilliant description of the reduced resonance signature of the turntable parts. BRILLIANT.
My experiments with plinths and platters show that you are right on spot ! |
Lewm: I agree with you that Win's Saskia is the closest approach to the ideal turntable. Resonant signature reduced to the max.Tight coupling bearing/tonearm. Deadened heavy platter. Slate plinth/tonearmboard. Idler drive. |
