Vintage DD turntables. Are we living dangerously?

My observation on coreless motors in direct drive turntables is that there are physical traits, at least the ones I owned and saw in pictures. Please keep in mind that I am not an motor engineer so my observation does not define what a coreless motor is.

(1) The most obvious is that the rotor magnet is always above the stator coils and there's small gap between magnet and coils. (Less "grip" on the coils and, not surprisingly, less torque.)

(2) The series of coils on the stator are ironless. (Helps to simplify its construction)

(3) Lower torque than typical core motor. (Not as dynamic sounding or less "jump" factor.)

(4) Many, not all, rotate smoothly even without the platter so they do not rely on the inertia of the platter mass like other DD motor. (This is an indication of its fluid sound.)

Here are some examples and observe the physical similarities.

JVC TT-101

Sony PS-X7

Sansui XRQ7

JVC QL-A2

Kenwood L-07D

Kenwood L-07D

Pioneer PL-50L II

Sony PS-X6

Kenwood KD770D

Dual 701

Brinkmann Bardo

Halco: "Doesn't it seem odd....if a coreless DC motor produces no cogging and sounds so 'fluid', relaxed and unfazed.....that a manufacturer would be foolish to even contemplate an alternative design?"

Coreless motors were utilized in most later models of many brands, especially in the late 70's and early 80's. Pioneer shifted to coreless motors in almost all their later models. Kenwood did the same starting with KD-770D and KD-990 -- I don't believe the KD-500, a model in the early years, uses a coreless motor. Sony used their version of the coreless motor called BSL (Brush & Slot Less) quite early in all their "PS-X" series. With the exception of Technics and Denon, almost all Japanese manufacturers shifted to using coreless motors in the late 70s and ealy 80's. Denon stubbornly stuck to their AC induction motor all the way through the 70s and 80s.

The earliest use of coreless in DD table is not even in Japan but in Germany. Dual used the earliest motors in the 701 in 1973, few years before the use of quartz lock drive. The motor model is EDS-1000.

Back to Halco's question. Many Japanese manufacturers did ask that question and they decided on the coreless motor. If given another decade to further develop motor in DD technology, I believe almost all would use coreless motor, given the trajectory of the trend in Japan. But CD ruined all of that. :(

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Hiho, The information I have been able to gather suggests that it is simply more difficult to get torque out of a coreless motor than out of a similarly sized cored motor because the coreless motors tend to trap heat and thus overheat, and overheating is lethal to them. (The iron or steel core in a cored motor also makes a good heat sink, so motors intended for heavy duty and continuous operation tend not to be coreless.) However, the Pioneer Exclusive P3 (coreless) motor is second only to the Technics SP10 Mk3 motor in terms of torque among the TOTL Japanese DD's, as far as I can find out. (Perhaps the Denon DP100 motor develops more torque than that of the P3; don't know. It's as big as a coffee can, so I would not be surprised.) If you read about Kenwood's thinking in the design of the L07D, they actually did not favor high torque in principle. So they were not concerned with competing in that "horsepower" race. Also, the drive system (the implementation of the servo mechanism, use of a quartz reference, handling of the AC and/or DC, speed of the sensor mechanisms, etc) are also determinants of the success of a DD design; cored motors can be made to work just fine, IMO. The fact that Denon and Technics stuck with cored motors does not necessarily mean they were "stubborn". However, like you, I am not a motor engineer. Motors and how they work, what makes one better than another for this or that application, are fascinating and complex subjects.

Apropos of that, you cite the Brinkmann Bardo for using a coreless motor, and I did too in one of my earlier posts, but does anyone know about the Grand Prix Monaco, the NVS, or the Teres Certus? For that matter, what about the Brinnkmann Oasis?

Lewm: "The fact that Denon and Technics stuck with cored motors does not necessarily mean they were "stubborn"."

Sorry, I did not mean to imply anything negative about Denon and Technics not using coreless motor. Perhaps the word "stubborn" was poorly chosen but was really intended to mean they did not follow the trend as they probably felt their DD development were mature enough to withstand the shifting trend. I know I like the sound of several Denon turntables, coreless or not. I know you like your DP-80. As for Technics, let me just say I am off the bandwagon.... but that's a different topic.

Lewm: "does anyone know about the Grand Prix Monaco, the NVS, or the Teres Certus? For that matter, what about the Brinnkmann Oasis?"

The only info on the Monaco I can find is from 6moons.com that says "The finalized Monaco turntable runs off a 5-8V 12-pole DC motor inside the main chassis." No indication that is coreless or not.

No idea what the NVS uses.

The Teres Certus uses a CORE motor from pictures I have seen of its innards.

The Brinkmann Oasis is the same as the Bardo, except it has a plinth. The Bardo is the stripped down version of the Oasis for a lower price.

Motors are fascinating indeed!

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Lewm: "If you read about Kenwood's thinking in the design of the L07D, they actually did not favor high torque in principle. So they were not concerned with competing in that "horsepower" race."

I think I agree with that thinking and from the sound of many DD turntables with coreless motors it only confirms that. I much rather have a smoother rotation than just high torque. Judging by the reviews of the Brinkmann Bardo, a low torque design, they are onto something and the impression is that the Bardo does not have the stereotypical sterile sound related to DD tables.

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Ah Radicalsteve,
The luxury of two TT-101s ?:^)
Interesting comments on the two metal mats.
I assume you are thus using no damping on the aluminium platter?
Can you describe the differences in sound you hear with these mats over the standard rubber?
Would be appreciated?