want new plinth ideas for direct-drive turntables

Hi Travis. Thanks for the input. I am aware of the Kenwood table and its "skeletal" mods. The motor is still attached to the stock frame. I want the motor completely detachable. I think the Kaneta mod is closer to what I am talking about, although hardcore Kaneta style even extends to a complete rebuild of the electronics and power supply. But that's the idea so I will loosely coined that as the "Kaneta style" by having the "nude" motor completely out of the stock chassis or plinth. I am not talking about "motor unit" or "motor assembly" that the motor is mounted to a chassis, typically aluminum structure with electronics and power supply and controllers like the SP-10 and then mount that to a wood plinth. Almost all Sony and Denon DD tables require a tape-head to read the magnetic info embedded on the rim of the platter for the servo system so a Kaneta style mod requires more work on mounting the tape-head precisely to track the magnetic rim. It's still do-able. I am in the process of yanking the motor out of the JVC TT-71 assembly and mount it on a solid wood plinth or slate plinth and extend the motor cables back to the stock chassis. Many later era JVC tables using the wonderful coreless motor are also great for such mods. I prefer a table that the motor is completely detachable from the electronics. A Technics SL-1200 motor is soldered directly to the circuit board so it's not a good candidate but the earlier SL-13/14/1500Mk2 series are great for Kaneta style mods.

Pioneer stuff are probably the easiest to do such mods and their bearings are of excellent quality.

Thanks again for your encyclopedic knowledge of Japanese electronics.

How's your DP-100 going these days? I am still salivating.

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Travis, the TT-71 is the typical servo quartz lock type right before JVC went bi-directional but TT71 and TT81 do share the same motor. So after the mod, if I ever find a TT-81, I can always plug the umbilical cord to it as an upgrade.

Yes, the SP-10 family is easy for this type of mod, just to note that the MJX-12A motor is pretty wide diameter (6 inches) compare to other DD motors, so you need to cut a pretty big hole. Here's an example of the Kaneta style:

http://homepage2.nifty.com/~mhitaste/audiotop/audio_apparatus_page/sp-10mk2.html

Yes, as I said, the Sony and Denon are doable but the requirement for precise mounting of the tapehead is a hassle so I leave them alone. But I am attracted by the nice motor in the PS-8750... and it's a beater. Hmmm...

Typical Pioneer motors from, say, PL-500, PL-600, PL-L1000, have a flat bottom so one can simply mount them on a flat surface without cutting a big hole. The earlier models such as PL-550, PL-570, require a 4" diameter hole on the plinth for mounting. All their motors contains the speed control requirement so no external hardware like tapehead is required like Sony and Denon. Admittedly, their sound to my ears is not as smooth as JVC stuff but perhaps with a plinth overhaul will push their performance a notch. Or maybe not. I did try their cheap models with coreless motor like the PL-300 and it has a smoothness reminds me of the JVC, so I am very curious about their later models like PL-70L that switched to coreless motors. Of course, they continued to use the superb Stable Hanging Rotor(SHR) bearing.

You have TWO DP-100?!! Wow. Lucky man. You have owned just about every top of the line Japanese DD tables in the golden era (1975-1985). What's your next conquest? Vintage European DD tables now like the EMT 950 or Goldmund Studio, etc...? Or the new generation of DD tables like the Teres Certus, Monaco Grand Prix, Brinkmann Bardo, etc...?

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Dertonarm, yes a DD tables are very suitable for suspended plinth. Unlike some belt-drive suspended tables that the motor is fixed and the platter and arm is suspended that creates speed issue. I believe the Goldmund Studio was one of the first expensive tables to employ suspension in the DD genre. It's definitely worth investigating. Thanks.

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I did not say taking the electronics out. I only want to take the motor (and platter) out of the stock chassis so it can be mounted on something more solid - Mike Lavigne's Steve Dobin plinth works the same way. The Kaneta approach is a radical one as it keeps only the motor from stock form and redesigned all the electronics from scratch using new circuits and power supply. I am not suggesting that and I simply do not have the knowledge nor resource to do that. Taking the motor and platter out of the stock turntable makes it flexible to implement new plinth design. The original electronics remains in the stock plinth/chassis/enclosure/whatever or you can house it in a different box. Yes, it will require extending the motor wires to reach the electronics.

I hope the "splainin" helps. Thanks for the interest.

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one cannot decouple the motor from platter in DD

It is possible to decouple the motor from the platter in DD. I was thinking about that the other day. Here's a concept turntable. The problem is that such design will have two layers and it will require having two bearings. One for the platter above and one for the dd motor underneath. Think of the EAR Disk Master turntable by having non-contact magnetic drive in concept but instead of having gear belt driving the subplatter underneath, simply use a direct drive motor. Another way of looking at it would be having a platter/bearing assembly at the top layer with a with a contact disc at the bottom of the bearing to make contact with the dd turntable at the bottom. Make sense? Here we can take advantage with decoupling and direct driving at center of the platter. Again, it's just a concept, whether that's practical to make or not is another issue. The Clearaudio Statement is similar concept except the lower platter belt-driven and again using non-contact magnetic pull to rotate the top platter.

Lot of fun ideas in the head. :-)
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Lewm, let me assure you that I am NOT a purist of any kind - in audio I am more of an anarchist. *Laugh*

Back to this concept turntable. I actually WANT to have a tiny bit of compliance to filter out whatever cogging inherent in a DD motor. I have done some experiment (nothing purely scientific here so please don't jump on me if you are militant about it) with using two DD turntables driving each other via a belt, an idler wheel, and direct-drive. Each one has its own sonic signature and the softer the compliance the softer the sound, the direct-drive being the hardest sound but also the most powerful sounding. Each has its plus and minus.

I also tried with DD tables with various torque, the higher torque the more powerful the sound but the lower the torque the smoother and fluid the sound. As you can see in these sonic results there's a relationship between torque and compliance. Of course, for me the ideal situation would be to have the perfect motor with zero cogging and go the purist direct-drive route. I neither have the resource nor knowledge to obtain such perfection so fiddling around is fun for me.

Anyway, what I am aiming for is a hybrid by separating the turntable from the motor in a direct-drive arrangement, that is, driving the platter right below the rotational center but also decoupling from each other. In the EAR Disk-Master and Clearaudio Statement, they go the route of non-contact magnetic force. I agree with Lewm that there must be some compliance between the connection gap so I would simply make them contact with some material from hard to soft (ranging from rubber to acrylic to metal to whatever) to "dial" in the compliance that would fit the motor behavior to filter out any cogging that remains.

The really tricky thing about this arrangement is the construction of the bearing since we need the bottom center to extend down to make contact with the motor below, that very center is where normally the thrust plate and ball bearing are in a conventional stick in a hole bearing. The EAR Disk-Master has to resort to "angular contact bearing", essentially a series of balls in a circumference instead of a single ball so they have the potential to be noisy.

One day I would like to find a machinist who can help me modify a platter and bearing so I can place it right above a conventional DD turntable like a Technics SL-1200Mk2 or motor unit of the SP-10Mk2. Essentially having a DD table at the bottom "centered driving" the above platter. Wouldn't it be fun to experiment with various DD tables in this arrangement to try them as a "motor"? My thought is that why re-invent the wheel when we already have so many DD turntables as motor in the used market. Just think of the possibilities. The EAR and Clearaudio could have used a direct-drive approach but instead they opted for belt drive, in fact the EAR uses gear belt to avoid belt slip. And the Clearaudio is essentially using one of them top belt-drive tables center driving a massive platter above it - not so clever.

There are really so many ways to make direct drive in terms of platter, bearing, rotor, and stator arrangement. Maybe I am losing some of you because I think like a deconstructionist or a gear head and whenever I see a turntable I see the sum of a platter/bearing/motor arrangement and automatically visualize each component individually and how each contribute the whole system. I NEVER see them as a box that plays records and that's the kind of disease that this hobby bought me. :-) I am an incurable tweaker when resource(money) and knowledge allows of course.

Thanks for indulging me, Lewm. :-)

Some pictures of the EAR Disk-Master and Clearaudio Statement:

http://www.dagogo.com/assets/images/image/EVENTS/2010%20CES/Coverage%202%20-%20Turntables/2010CES-2-EAR.jpg

http://www.positive-feedback.com/Issue34/images/019_EAR_turntable.jpg

http://www.enjoythemusic.com/rmaf_2007/friday/disc_master_belt.jpg

http://lh6.ggpht.com/headfi/R4_D1PGuqNI/AAAAAAAAADg/it_dJNpjqlA/s400/IMG_7850.JPG

http://www.clearaudio.de/download/presse/statement_presskit_07_en.pdf

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Very nice. It's about time someone take the motor out of the damn SP10 chassis! Why do you sink the platter so deep into the slate? Wouldn't the shortness of the platter limit the choice of tonearm? Isn't this much like Lenco stock top-plate that people have to cut out a hole and sink the arm mount area to allow more arm choices? When I used to have the SP10 I always wanted to lift the platter higher so I can use it to belt-drive another platter. Anyway, it's good to see such product exist. Thanks for sharing.

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Now, that's the Kaneta spirit! That's exactly what I am talking about! Thanks again Weisselk for alerting me that. Almost all vintage DD tables can be improved this way. I have seen and owned so many DD tables whose performance suffers so much from bad plinth when their guts have so much potential. I don't care how fancy the plinth is if you don't take the motor out you are still using a flimsy chassis to house all the motor, electronics, and power supply rattling inside.

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I never had the fortune to listen to an L07D but from a design standpoint it is worthy of its billing as a top of the line model and a world class DD table, so I am envious of you, Lewm. (coreless motors are wonderful, aren't they?) Yes, when I look at it the designers were thinking along the same lines. With that in mind, we can apply that to less expensive models of different brands. If the renaissance of plinth building for vintage idler-drive tables can be an inspiration, we can start address many underrated DD tables and explore their potentials all at a very reasonable price. Since many people are comfortable with Technics products, I recommend the SL-1300/1400/1500MK2 series as the motor is detachable from the electronics and their platters are much heavier than the ubiquitous SL-1200Mk2 and they are balanced with drill holes at the underbelly. The arm is mediocre so no loss if you gut it.

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The SP25 is not doable because it is essentially the same motor(and electronics) as the SL-1200Mk2 therefore the motor is attached to the pcb or to be precise the stator wires are soldered directly to the pcb, not a good candidate. The SP15 is doable as long as it's not too expensive for you to do this experiment - actually a very good candidate. I have one too but I need that for something else. The SL-1300/1400/1500Mk2 series is perfect for that because the motor is very similar to the SP15 and the electronics share the same chips! And they are inexpensive (used to be dirt cheap at one point) but do make sure you get one that its platter does not rotate in reverse or rocking back and forth, very common issue with them. My favorite is the very rare SL150Mk2, an armless and non-suspended version of the SL-1500Mk2. Oh, the SL-1301 and SL-1401 would work too but they have lighter platter. Overall the SL-1500Mk2 is ideal, if you can get one cheap.

As I said before, Pioneer integrated tables are the easiest in such models like PL-500, PL-600, PL-L100, (all 3 motors are swappable with each other's electronics) and the shortie PL-300 is a smoothie due to its coreless motor with Pioneer's SHR(Stable Hanging Rotor) bearing. Pioneer repeated some of their model numbers so they can be confusing and the ones I mentioned all have S-shaped tonearms. The earlier pre-SHR period Pioneer tables like PL-550 and PL-570 are excellent and easy to implement. I used them to belt-drive my passive platter but they are good performers on its own.

Bear in mind that this mod is reversible because you are just taking the motor out and rout the cable into the stock chassis so if you don't like it you can return to its stock form. If you get good result you might never want to put the guts back into the stock body again. You can of course house the electronics in another enclosure like the OMA SP10. All I am saying is that there are so many good DD tables out there with excellent guts waiting to be exploited. The best is to have a beater and have some wacky fun with it. :-)

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Due to financial situation, I was forced to sell all my SP10s. :( I still have some DD tables from various brands and a Lenco. Currently I do not have any belt-drive tables so I don't even qualify as an audiophile. :)

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Thanks for sharing, Borning50. Speaking of Pioneer, here's a PL-30L that got an overhaul by a Japanese audiophile that's pertinent to my idea. The motor is very similar (probably the same) to the one in my PL-L1000 linear tracking table. Since the bottom of the motor is flat, you don't even need to cut a big hole on the plinth. A great candidate for such mod.

Check out the links to other cool stuff, including a linear tracking arm using motion control glides from THK. Very cool.

http://kiirojbl.exblog.jp/i108

http://kiirojbl.exblog.jp/i109

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The 518 project is not mine, although I do have a footless 518 waiting for surgery! :)

Glad you have a beater to experiment with. To be honest, the 518 is not the best candidate. I had a similar one like that. I forgot the model number but it didn't keep speed and had jerky motion. After several bad experiences with early era DD tables, I decided not to touch anything that's made before 1975 or pre-quartz-lock era. Back to Pioneer, I have a PL-570 is just about perfect for such project - currently in "guts" form with only motor and electronics and power supply - and I think the simpler version PL-550 is even better. I know some people are attracted to the wood veneer and probably pains them to do butcher them. The cabinet is really resonant and easily attracts acoustic feedback so butchering it is no loss to me as I hate plinths that shape like a box (and that includes certain Scottish spinner). I try to look for units that have broken or nonfunctional tonearms or bad auto mechanism, as long as the motor and drive electronics works, they can be had for dirt cheap. It's fun to experiment with beater tables. :-)

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I love this plinth!!

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I never own any Sansui turntable, even though I am a huge fan of their tube gears - awesome output transformers. I am not familiar with that model but I don't think the motor is all that interesting. And judging by the look of it, they might have outsourced it from Denon. As a turntable, I would rather choose their later day coreless motor models like XP-99 or XR-Q7. As you know I am a big fan of coreless motors - super smooth sound. The attraction for me is the tonearm as it is knife edge design a la early SME but the horizontal movement is an inverted bearing on sapphire disc. Very unique for its time. Anyway, the table seems well built and might be a good performer.

Almost all info on Sansui turntables can be found on this site:
http://www.classicsansui.net/Turntables.htm

I have read about Sansui's latter day designs in addressing the counter torque issue with direct-drive motor by adding another motor underneath running in reverse to cancel the vibration. Not the most elegant solution but at least they acknowledge the issue. I much prefer Steve Dobbins' simpler and more elegant solution by decoupling the stator coil from the bearing assembly. Judging by the look of theXR-Q7 motor, Sansui might have outsourced that from Sony as it just like the BSL (Brush/Slot-Less) motor from a PS-X40, PS-X70, and others, even down to the tapehead servo system. Those BSL motors have rather flimsy construction on the bearing well as it is mounted on plastic(!!) as my PS-X65 got damaged in transit due to bending plastic. Maybe Sansui improved on it. Anyway, those two models, XR-Q7 and XP-99, are the only Sansui turntables have any attraction to me. Unless I find a beater XR-929 so I can scavenge the arm. :-)

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You don't need Sansui or Micro-Seiki for direct-drive, because you already own one of the best DD tables ever built, the Kenwood L-o7D. :)

I own a Kenwood KD-770D and it's super smooth with probably the lowest torque among DD tables. It has a fluidity almost like a belt-drive but DD speed stable. Again, a coreless motor unit along with its bigger brother KD-990D. I can imagine how nice the LD-07D can be... I believe it's a high torque design so its bass must be awesome. Lucky you.

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