Brinkmann Bardo

Dear Wjsamx, The Kenwood L07D slotless, coreless motor also uses assymetrical placement of the coils of wire that form the stator. In addition, the rotor (magnet) in the L07D motor is parallel to the horizontal plane of the platter, as in the Bardo. I believe there is a sound reason for the assymetric coiling, although I have been puzzling on it since I took apart the motor of my L07D. (Photos of the coils in an L07D can be seen on the L07D Lovers site.) But it is a bit presumptuous to state that the similar arrangement in the Brinkmann is going to result in undesireable "non-uniform pushing and braking", unless you are an engineer and can back it up. To me the assymetry is so obvious that it must be deliberately done for a good, i.e., beneficial reason. Also, the Brinkmann motor is much more like that of the L07D than it is like those of the Technics SP10 Mk2 or Mk3. In the Mk3, the stator/rotor interaction occurs in the vertical plane, and of course the multi-pole stator has a core.

Thank you for your explanation on the Dual EDS motor, Wjsamx. It's fascinating. I have a Dual motor like that as parts but unfortunately it has scraping noise and I don't have the complete power supply. I would love to be able to make it work and have a listen. After reading your post, even more so.

On Brinkmann's technical white paper, which provides interesting reading, in discussing the drive mechanism, it does mention the arrangement of the stator:

The motor’s stator consists of four specially designed field coils, which are mounted concentrically with high precision around the platter bearing. Based on listening and tuning sessions, we decided to forgo the typical 90-degree mounting angle in favour of a non-standard 22.5-degree raster, which, due to the magnetic fields overlapping, further reduced cogging. The motor’s rotor also acts as the sub-platter and carries a magnetic ring with 8 poles on its underside.

The drive mechanism, based around Hall sensors and an encoder disk, is designed in such a way that there is just enough power to bring the 10 kg heavy platter up to 33 ! e rpm in about 12 seconds. Conversely, only a minimal amount of energy is actually necessary to keep the rotational speed at a constant. While the drive mechanism is indeed direct, power is actually transferred without any contact.This soft coupling via a low power magnetic field translates into a silent drive, which reduces cogging further. One of the main attributes behind the sound quality of the “Oasis” has to do with our proprietary motor control. It works proportionally, i.e. it transfers just enough energy to the motor for it to remain at constant speed. Conversely, due to our ultra low-friction bearing, only a small amount of energy is actually necessary to keep the motor at constant speed. Previously available regulators typically work disproportional and rather abruptly: they speed up and slow down the motor very rapidly when necessary.

During the development phase of the “Oasis” turntable, we spent many long hours auditioning several different regulator designs; it became quite evident that utilizing our concept of proportional regulation always resulted in better sound: typical “harder” motor control concepts produced a sound significantly lower in quality, with less color and drive.

I do believe the Brinkmann motor is quite different from Technics. Many Japanese manufacturers switched to coreless motors in the late 70's to early 80's such as Sony BSL motor, Pioneer in the later SHR motors, Kenwood in their KD-770D and KD-990, almost all JVC QL series tables. Technics, however, stayed with core motor through that era. Reportedly coreless motors sacrifice torque for smooth rotation and less cogging. I am not an engineer so these are all based on visual observations of the physical motors that I have open apart.

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Hiho, That stuff could have come directly from literature on the Kenwood L07D. The speed control works the same way, using "proportional regulation". There are an optional platter ring and central weight to add mass to the L07D platter. When those are in use, you have to "tell" the power supply, and it alters the speed correction algorithm accordingly. Speed stability depends in part upon platter mass, rather than on super-high torque, in contrast to the Technics dd turntables. There is nothing new under the sun. The Bardo looks to be a great turntable. What does it cost?

"power is transferred without any contact" - that could be said of any direct-drive turntable wherein the magnet (or rotor) is part of the platter and the stator is mounted around the bearing assembly.

The cost is about 7-8000 dollars.

Lewn: "There is nothing new under the sun. The Bardo looks to be a great turntable. What does it cost?"

According this site, the retail is $7,990.00 USD so each coil is about 2 grands. :)

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