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any difference between magnetic drive & direct drive ?

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Posted on March 24, 2010 at 11:06:31
caligari
Audiophile

Posts: 415
Joined: March 20, 2008
Recently I hear the terms "magnetic-drive" more ever since Brinkmann introduce their Bardo model, a stripped down cheaper model from their Oasis. From all the pictures I've seen, looks like it uses a coreless motor and I wonder how is this different from direct-drive? I'm sorry, it's a just a direct drive with a coreless motor, nothing new here. Unless someone can illuminate me on this, I see no difference.

When the motor and platter share the same bearing, it is direct-drive!

Pictures of the gut.
http://www.my-hiend.com/michael99/20091002_Tokyo_Audio_Show/20091002_543_409_35.jpg
Stator: http://www.vinylengine.com/phpBB2/album_pic.php?pic_id=8013&full=true
Rotor: http://www.vinylengine.com/phpBB2/album_pic.php?pic_id=8014&full=true

Pictures of Bardo and Oasis that share the same gut:
http://www.onahighernote.com/brinkmann/?c=2
http://www.onahighernote.com/brinkmann/?c=5

- - - - - - - - - - - - - - - - - - - - - - -

The only turntables that I am aware of that can qualify to be called "magnetic-drive" are the Clearaudio Statement and EAR Disk-Master, that the platter is separate from the motor and is driven by a subplatter underneath(essentially a belt-drive turntable) via magnetic pull.

http://www.clearaudio.de/eng/lw_statement.html
http://www.clearaudio.de/download/laufwerke/statement/statement_en.pdf
http://www.clearaudio.de/download/laufwerke/statement/testbericht_statement_absolutesound.pdf

http://www.ear-usa.com/ear_sources.htm
http://www.ear-yoshino.com/pdf/Hi_Fi_Choice_Turntable_Reprint_Edition.pdf
http://www.positive-feedback.com/Issue41/ear_diskmaster.htm


 

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RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 12:11:14
cactuscowboy@bresnan.net
Audiophile

Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007
 Accepting that your premise is correct, I'm guessing the difference is this:

DIRECT DRIVE - Excellent drive system unfairly and unjustly maligned by audiophile snobs clinging to stubborn myths.

MAGNETIC DRIVE - New and clever marketing terminology intended to appeal to audiophile snobs.

:-)

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 12:22:03
Tedmc
Audiophile

Posts: 368
Location: So Calif
Joined: November 6, 2004
 DIRECT DRIVE: Cheap drive system utilizing 7 magnets/poles mounted closely to the spindle.These were popular with cheap Japanese TT's. The worst place to mount a drive system is close to the spindle bearing.This creates a 7 pole motor generating energy directly into the chassis/platter in close proximity to the bearing/spindle.
MAGNETIC DRIVE: Elegant drive system as used by Grand Prix/others. Utilizes 192 or more magnets/poles at the outer rim of the platter (allows computer control of electricity to the drive system) Places the motor as far away from the critical bearing/spindle as possible.

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 12:38:34
Lew
Audiophile

Posts: 11011
Location: Bethesda, Maryland
Joined: December 11, 2000
 Dear Tedmc,
That must be why those Japanese turntables (admittedly, the better ones, not the "cheap"ones) had S/N and wow/flutter numbers comparable to and sometimes better than many of the best of modern belt-drive turntables, along with superior speed stability under load.

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 12:40:13
Tedmc
Audiophile

Posts: 368
Location: So Calif
Joined: November 6, 2004
 And how about the "Rumble" figures rated as (-db)?

 

Funny...., posted on March 24, 2010 at 13:16:48
Biff
Audiophile

Posts: 7533
Location: Portland, Oregon
Joined: January 27, 2002
 The Technics SP10 had a rumble figure of better than -60db. Is that bad? :)

 

-60?? Try -78dB /nt\, posted on March 24, 2010 at 13:24:50
Opus 104

 

RE: Funny...., posted on March 24, 2010 at 13:25:39
Tedmc
Audiophile

Posts: 368
Location: So Calif
Joined: November 6, 2004
 I think the SP 10 is better than -60. Here is the rumble figure from a Stereophile review of the Basis Ovation:
(Rumble: –90dB DIN Standard)

 

RE: -60?? Try -78dB /nt\, posted on March 24, 2010 at 13:28:49
Biff
Audiophile

Posts: 7533
Location: Portland, Oregon
Joined: January 27, 2002
 I got that right off their brochure. Everybody must be hitting the vinyl engine now because it stopped responding.

 

Nope. Get my Technics info here (link), posted on March 24, 2010 at 13:30:20
Opus 104

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 13:41:07
cbrady
Manufacturer

Posts: 188
Joined: January 14, 2002
 You are correct that direct drive means that the motor and platter share the same bearing.

Magnetic drive is a more ambiguous term. Every electric motor in existence is has magnetic drive. The rotor of the motor is driven by magnetic pull from the stator. And just like the coupling methods used by EAR and Clearaudio this magnetic coupling is "stretchy" much like a rubber belt. The compliance of the field in the motor is directly proportional to it's torque capability. I don't see how using a powerful motor connected to an EAR type magnetic coupling scheme would be any different than just using a weaker motor without the magnetic coupling. Please correct me if I am missing something. So magnetic coupling is also a marketing term for a scheme that adds a layer of magnetic compliance in series with the motors internal magnetic compliance. Much like a stout rubber belt driving another more stretchy rubber belt.

The Grand Prix motor is a very good implementation of direct drive, but is not any more or less "magnetically coupled" than any other electric motor.

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 13:41:54
caligari
Audiophile

Posts: 415
Joined: March 20, 2008
Talking about specs has NOTHING to do with the fundamental question here, that is, what is the difference between "magnetic-drive" and "direct-drive" in its mechanical and electrical design. I an not looking for a quantifying but qualifying answer. I see no difference at all other than just a marketing ploy to diffuse the bad rap the direct-drive genre got from the early days. As long as the platter and motor shares the SAME bearing or bearing shaft, there is NO difference!! The platter is still being driven by the motor below and ALL motors operates with magnetic propulsion. Comparing specs is like saying a SmartCar is not a car because its not long enough! This semantic silliness with word game using "magnetic-drive" to replace direct-drive seems to me the marketing people's ploy to exploit the potential buyer's insecurity. It's like a George Carlin joke, you are not short, you are just vertically challenged!


 

Does any of this matter?, posted on March 24, 2010 at 13:42:25
Biff
Audiophile

Posts: 7533
Location: Portland, Oregon
Joined: January 27, 2002
 What I mean is, are these numbers worse than a decent BD table?

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 13:43:17
cbrady
Manufacturer

Posts: 188
Joined: January 14, 2002
 So why is having the drive system close to the platter bad?

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 13:52:53
Tedmc
Audiophile

Posts: 368
Location: So Calif
Joined: November 6, 2004
 Mechanical resonances.And the close proximity to the critical bearing.

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 13:58:15
cbrady
Manufacturer

Posts: 188
Joined: January 14, 2002
 Sorry I meant to say bearing not platter. To repeat, why would placing the drive in proximity to the bearing make mechanical resonances or any other issues worse. The bearing is indeed critical, but how would having the motor components close by make things worse than if they were moved farther outward?

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 14:00:38
Tedmc
Audiophile

Posts: 368
Location: So Calif
Joined: November 6, 2004
 You misunderstand that the Japanese TT mfr's coined the marketing term "Direct Drive" 35 years ago.They are all magnetic drive as a class.

 

I'm with ya buddy, agree 100% NT, posted on March 24, 2010 at 14:01:52
cactuscowboy@bresnan.net
Audiophile

Posts: 7738
Location: Powell, Wyoming
Joined: July 23, 2007
 xxxxxx

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 14:06:52
caligari
Audiophile

Posts: 415
Joined: March 20, 2008
There you go! No difference!

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 14:08:53
Tedmc
Audiophile

Posts: 368
Location: So Calif
Joined: November 6, 2004
 Having mechanical energy/resonances in close proximity to a main bearing is not a bad thing at all (in and of itself)...as long as there is no energy actually reaching/interfering with the bearing itself and causing measurable distortion.

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 14:11:11
Tedmc
Audiophile

Posts: 368
Location: So Calif
Joined: November 6, 2004
 I see...my bad, I actually thought you were asking a question ...and instead you were trolling for a response..

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 14:22:50
caligari
Audiophile

Posts: 415
Joined: March 20, 2008
I think your term "magnetic coupling" is better suited to the Clearaudio Statement and EAR Disk Master. I was just thinking out loud on products that fit better with the "magnetic-drive" moniker. That's all. When I read about those two products I was disappointed that no one has used a direct-drive motor underneath the top platter - well, at least the EAR uses gear belt to avoid slippage, I guess... . I agree with your assessment of their implementation - I think the selling point is that there's no physical contact between the two rotating masses. In this scheme, I like the idea that the platter is being CENTERED driven but they could have used a DD motor instead.


As long as we know what direct-drive is, we can cut through the marketing bs.

 

Be careful of DIN numbers, posted on March 24, 2010 at 14:30:25
travisty
Audiophile

Posts: 1368
Location: Tokyo
Joined: April 2, 2003
 In 1976 when the SP=10Mk2 was released, the DIN A number was -60. The DIN B number was -78dB. In 1981 or 1982, the Japan Electronics Industry Association changed the way DIN measurements were made for consumer electronics, moving from the worldwide system then in use, derived from Fletcher-Munson curves, to something where an additional filter was added to shift the weighting of the measurements to significantly downplay the areas around 50-60Hz (basically pretending transformer hum did not exist).

An example of the change is that the Exclusive P3 released in 1979 has a DIN B measurement of -78dB, and the 1983 P3a was -95dB. The P3a has few things changed other than some minor motor circuit modifications, a different phono cord and power cord composition, and a damper added to the armtube, and of course the price - allowing them to charge more after a period of strong inflation. The Pioneer service center tells me that when he services them, he tests all the tables as they go out the door (though it is not on the spec sheet they give you after an overhaul) and the P3 and the P3a are, statistically speaking, identical (using the revised DIN B) at around -95dB.

This would make it, and several of the top (or even non-top-notch) DDs from the early-mid 80s a bit quieter than the Basis Ovation.

Among DD tables of the time, the much better way of comparing amongst them, when you can find the data, will be to compare using DIN A or JIS (Japan Institute of Standards) measurements, because they did not change. However, no modern table does/releases that measurement so it is difficult to bring forward in time.

I have never seen a number for a Micro Seiki air bearing table. It is clearly quieter than my DDs, but part of that is the built-in isolation system in the bearing. Putting a DD table onto an isolation table will do wonders for its noise level. Putting the MS onto an isolation table does additional wonders for it changing the game again.

Biff's response is the correct one. The answer is "no, not really." Once you get into "really quiet," the method for getting even better is to reduce bearing friction, and to reduce outside noise interference with a good suspension or isolation system which knocks the resonant frequency of the motor/disk interface to something with a 2Hz-handle. This is why the best DD tables of the early 1980s had both a lot of weight and a decent isolation system (dampened/loaded springs like the Exclusive P3 and DP100 and PS-X9, or springy isolation footers like the original feet on the SH-10B5 plinth for the SP-10Mk3 and others like the Lo-D and I think the Onkyo). Some went a step further and introduced a dual-layer platter with a suspension between them to dampen motor vibration further.

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 14:32:06
cbrady
Manufacturer

Posts: 188
Joined: January 14, 2002
 The EAR approach has the common characteristic with direct drive of no physical contact. But I think that the resulting sound would be much more like belt drive than direct drive.

 

RE: any difference between magnetic drive & direct drive ?, posted on March 24, 2010 at 14:52:44
caligari
Audiophile

Posts: 415
Joined: March 20, 2008
I agree. Since the sliver of magnetic field between two rotating masses is compliant so it is acting like a rubber belt and I can imagine it having more of a "belt-drive" sound.

I would replace the bottom assembly with a DD motor and instead of magnetic coupling, I would try have contact and drive it and experiment with different coupling material from soft to hard. And if this material is close to the property of an idler wheel, it just might have an idler sound. Of course the hardest would simply be a direct-drive turntable. :-)


 

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