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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DP-100 spinning tunes as I write. Love it. Only need one though so the other is going to go... :^)

One might be able to wrap the electronics in TI Shield or something similar, and leave them there (like the board in the casing of the SP-10Mk2) but if one wanted to separate the brains from the brawn completely, it should be doable with an umbilical in all but a bare minimum of cases. I recently saw that someone had taken it out and run a larger chassis cord (with larger wire count) from the motor to an outboard box). The SP-10Mk2 is eminently suited to that from what I understand of its innards. As for the Sony and Denons and the 'tapehead'... I would have to imagine one could simply take the 'brains' off-board. If one wanted to remove the entire head assembly from the mounting under the platter (as it is attached to the motor housing), and go completely naked, re-installing it correctly might be a major hassle, especially if you wanted a plinth of slate (I'd mock up the topside in MDF or plywood before doing it). Off the top of my head, I cannot remember the speed-control technology in the circuitry of the TT-71; the bi-directional-servo starts with the TT-81. I am not sure why the Pioneers would be particularly easy to do the mods on but I'll take your word for it.

In any case, your project is an interesting exercise and I expect might be worth the hassle for a DIYer. Once I get get some space, I might try doing that with a beater I have...

I know its not popular, but go and try once for heaven's sake a plinth which is suspended with low resonance frequency - below 3Hz.
It is not the plinth weight, composition or raw material - isolate it from any outside vibration and your eyes will pop wide open how the sound and stability change for an unknown quality.

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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Need some 'splainin' here, as Desi Arnaz used to say.

I don't know all that much about electronics and I'm only familiar with the SP-10 Mk 2 series of DD tables. But since the motor must remain attached to the spindle and platter, how much benefit can be gained by moving the circuit boards outboard? It seems to me the biggest potential problem could come from the current field of the motor itself, rather than the circuit board(s). For this reason the addition of an EMF/FRI shield such as recommended for the Kenwood L-07D, suggested by T_bone above, and implemented by Albert Porter in his SP-10 tables, would be as good an upgrade and far simpler and cheaper.

Concerning Dertonarm's suggestion for suspension to isolate outside vibrations, would not the high torque motor of the better DD tables be the largest source for micro-vibrations in most set ups? How would suspension address that?

Thanks for any more light on these thoughts.