This is my first DiyAudio post! I write as I'm preparing to build my first turntable plinth.
My starting point is a Micro Seiki DD-8. Micro Seiki DD-8 Direct-Drive Turntable Manual | Vinyl Engine A well-regarded direct drive table. I'll be using the motor and electronics from the DD-8 along with "upgraded" platter and tonearm. The platter is from a DD-8Z/DDL-120 (4.5kg vs 2.6kg for DD-8) and the tonearm a Micro Seiki MA-505 MkIII (vs MkI)
My hope is to take a successful table and upgrade it in a number of modest and hopefully beneficial ways. For example, the platter is bigger but still capably turned by the same motor in other Micro tables. The tonearm is an improved version of the original tonearm. I'll be moving the electronics off of the plinth and into a separate housing, much as Micro did with the DDL-120 and other higher-end tables. There will be many other variables to consider, presumably after the table is built.
The DD-8 plinth is very basic - three layers of particle board, glued together. My goal is not to build the perfect plinth, but to do "better" than the original. (And I'll say up front that I know that simply "upgrading" a few components does not guarantee success. Everything needs to work together.)
As for plinth design, the principles seem to be well agreed-upon in that the table should be sufficiently rigid, lossy, and massive - and that there are no perfect materials. So composite "sandwich" structures are often used, which blend materials in a manner that results in better damping than would otherwise occur from any one of them alone. Within that context, there are clearly different views and experiences with what works best. Of course it's important to ensure the platter bearing and tonearm are sufficiently isolated from each other and of minimizing interference from outside disruptions.
I have a masters in science, but haven't had the pleasure of applying it professionally for a long time. And I have no plinth-building knowledge of my own. So I'll probably be able to understand the technical stuff it's well-explained and I can ask follow up questions 🙂 Also I'm a capable wood worker with a garage full of tools. I don't have the ability to work with anything exotic though. (So panzerholz is out)
Again, I'm not out to build the perfect plinth. Just to do "better" via the application of simple principles and the experiences of other DIYers. And to learn a bunch in the process so I can go further next time.
My starting point is a Micro Seiki DD-8. Micro Seiki DD-8 Direct-Drive Turntable Manual | Vinyl Engine A well-regarded direct drive table. I'll be using the motor and electronics from the DD-8 along with "upgraded" platter and tonearm. The platter is from a DD-8Z/DDL-120 (4.5kg vs 2.6kg for DD-8) and the tonearm a Micro Seiki MA-505 MkIII (vs MkI)
My hope is to take a successful table and upgrade it in a number of modest and hopefully beneficial ways. For example, the platter is bigger but still capably turned by the same motor in other Micro tables. The tonearm is an improved version of the original tonearm. I'll be moving the electronics off of the plinth and into a separate housing, much as Micro did with the DDL-120 and other higher-end tables. There will be many other variables to consider, presumably after the table is built.
The DD-8 plinth is very basic - three layers of particle board, glued together. My goal is not to build the perfect plinth, but to do "better" than the original. (And I'll say up front that I know that simply "upgrading" a few components does not guarantee success. Everything needs to work together.)
As for plinth design, the principles seem to be well agreed-upon in that the table should be sufficiently rigid, lossy, and massive - and that there are no perfect materials. So composite "sandwich" structures are often used, which blend materials in a manner that results in better damping than would otherwise occur from any one of them alone. Within that context, there are clearly different views and experiences with what works best. Of course it's important to ensure the platter bearing and tonearm are sufficiently isolated from each other and of minimizing interference from outside disruptions.
I have a masters in science, but haven't had the pleasure of applying it professionally for a long time. And I have no plinth-building knowledge of my own. So I'll probably be able to understand the technical stuff it's well-explained and I can ask follow up questions 🙂 Also I'm a capable wood worker with a garage full of tools. I don't have the ability to work with anything exotic though. (So panzerholz is out)
Again, I'm not out to build the perfect plinth. Just to do "better" via the application of simple principles and the experiences of other DIYers. And to learn a bunch in the process so I can go further next time.
Hi Downupside, I've moved your thread from construction tips to Analog Source as I think it far more likely it will get the input you seek in this forum.Welcome to the forum! 😀
I'm building a TT using a constrained layer plinth from Victor, using a TT 71 Victor motor drive unit. The plinth is a Victor CL-P2, you can do a search and see how it's a 7 layer sandwich of alternating materials.
Victor knew a thing or two about TT, they were heavily involved in the broadcast industry and gave us things like quartz locked DD motors. They also supplied motors to Micro Seiki for a lot of their direct drive machines.
Billwojo
Victor knew a thing or two about TT, they were heavily involved in the broadcast industry and gave us things like quartz locked DD motors. They also supplied motors to Micro Seiki for a lot of their direct drive machines.
Billwojo
Search is your friend
Do a titles only search here for “diy cld plinth design” by a fellow named Pyramid for starts.
Enjoy your journey
Dennis h
Do a titles only search here for “diy cld plinth design” by a fellow named Pyramid for starts.
Enjoy your journey
Dennis h
Have you considered resin/bentonite. It's not as easy as a plywood plinth but they do work extremely well. There are a few of us that SP10's in resin plinths and the results are exceptional.
I've read this thread several times now. It's fascinating and backed up with testing. Ignoring the disagreements over what is truly CLD and what isn't, Pyramid has provided a really interesting model to consider. The disappointing part of that thread is that addition to going from the original plinth to his custom plinth he also chose to change tonearms. Which means there's no way to know truly how much of the difference is due to the plinth and how much the tonearm.
There of plenty of other folks who seem to focus on and swear by designs that involve more than three layers and more than two materials. Which leads me to wonder why one wouldn't start with a CLD design and add additional layers to help collectively ensure that whatever resonance remains is damped by additional materials with different acoustic characteristics.
As I said at the beginning, I have a science background but no expertise in this area. I did a lot of work in optics and spectral filters. So in my head, I think about a blackbody emitter like the sun that puts out a full spectrum of emissions. And what happens when you place a spectral filter in between that emitter and a spectrometer. The filter only lets light through via a certain and limited spectral range. If you add a second filter with a non-overlapping band of transmission, the two will collectively block all the light from reaching the spectrometer.
With CLD and acoustics, you've got two materials with different acoustic characteristics. Those characteristics are of course more complicated than in my simple example above AND are altered when the materials are joined together. But I have to imagine that a simple two-material CLD combination will not get rid of all resonance and that what resonance remains will have a spectral signature. And so I wonder why an additional layer with distinctly different damping/resonance characteristics couldn't effectively be used to absorb much of what's left.
So back to my light-based example. If the two filters have some overlap in their transmission ranges, they will still let some light through. A third filter could easily be used to block what remains. Why wouldn't the same sort of approach generally hold true with resonance in a turntable plinth?
To be clear: I'm not saying that I think these are the same. I know they're not. What I'm hoping for is to understand the limits of my thinking which will help me understand how to proceed.
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In regards to the resin with bentonite... Yes, i've read about these. Do you have to mold them yourself?
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Wrong there, sorry.
This "isolation" you speak of is detrimental to any turntable arrangement.
The platter/bearing and tonearm MUST be rigidly locked together to eliminate any interference.
I don't know where you gained that information, because it's just wrong design.
Yes you need to make a mold and inserts for any large holes as this stuff kills tooling pretty quickly. I used form ply which is what is used to form up for concrete as nothing sticks to it. These resin/bentonite plinths are about the best for a non suspended TT without going to Panzerholtz which is expensive.
The next plinth for chassis-less SP10 I'm going to make a timber box with a thin ply top and brace the inside between the motor and tonearm mounts with aluminium angle to increase stiffness. My theory is that the aluminium embedded in the resin/bentonite will dampen any motor vibration from reaching the tonearm
Rigidity as has been said is critical between the spindle and tonearm mount. Any micro movement will colour the signal.
I agree with wiseoldtech 100% on this, completely within the range of my own experience with the two TD124 I own, and the sub-chassis tables I owned in the past including a TD-125 and 5 AR-XA with various modifications. (By definition they would be tightly coupled main bearing to arm.)
The SME 3009/3012 Series II Unimproved had rubber grommets to isolate the arm from the arm board, I found this so objectionable I removed them and still recommend to friends who use these arms to do the same.
Would you care to offer some perspective? Many belt drives have a solid metal coupling between the platter bearing and tonearm. But I've been told this doesn't make sense with direct drives, being that the dd motor is directly coupled to the platter bearing. So if they are all coupled tougher, vibrations from the motor have a direct conduit to the tonearm via the metal coupling. So I could use some help clearing this up.
So what's the best way to ensure sufficient rigidity on a direct drive table? Again, as in my earlier response, a metal coupling would ensure complete rigidity but also provide a direct route for any vibrations to go from motor straight to tonearm. Makes sense on belt drive. But direct drive? I intend to mount the dd motor to the plinth, with the platter bearing clearly then held in place by the motor. And to mount the tonearm via a rigid armboard to the plinth. Is that somehow insufficient? Seems to be the way many high-end dds are constructed.
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I would suspect the Micro Seiki bearing/motor is very good and unlikely to transmit much noise. I have listened to both of my SP10's with a stethoscope and can hear no bearing noise. I haven't measured it yet this I will do once Ihave the new plinth made.
If the coupling between the arm and spindle is not rigid you can get micro movements between the arm and LP. The stiffer the coupling the higher the resonant frequency of the coupling. Higher frequencies are far easier to damp than lower frequencies.
Now to the resin plinth the resin/bentonite damps vibration very effectively and with enough thickness provide good rigidity. My current R&B plinth is 90mm thick.
I plan on making a new plinth. A timber box with aluminium stiffening under the top plate. Adding the aluminium bracing will stiffen the whole structure and because the aluminium is embedded in the resin it will also be damped.
If the coupling between the arm and spindle is not rigid you can get micro movements between the arm and LP. The stiffer the coupling the higher the resonant frequency of the coupling. Higher frequencies are far easier to damp than lower frequencies.
Now to the resin plinth the resin/bentonite damps vibration very effectively and with enough thickness provide good rigidity. My current R&B plinth is 90mm thick.
I plan on making a new plinth. A timber box with aluminium stiffening under the top plate. Adding the aluminium bracing will stiffen the whole structure and because the aluminium is embedded in the resin it will also be damped.
Real life is a lot more complex than hanging on to simplifications like rigid couplings.
Look at Linn who started the rigidity religion with the LP12. Right in the middle of those rigid couplings they introduce a soft and lossy armboard and use some flimsy fixings between it and the subchassis. Why? Because the rigid couplings are excellent transmitters and generators of bad sounding resonances. At some frequencies you need a bit of filtering action.
Took me a while to realise the ultimate rigidity concept is seriously overstated. How can air bearing tonearms be so successful if rigidity was so important? What about tonearms floating in oil? Or free standing armpods?
All really successful plinths are the results of many trials and errors, not of some brilliant simple concept or expensive materials.
Just what vibrations would be the issue?
A Direct Drive motor revolves at 33 or 45 rpm to spin the platter.
The flywheel effect of the (heavy) rotating platter damps any minute (read-extremely tiny) pulses generated to make the motor revolve.
The result is a smooth, constant rotation, free of any audible flutter.
These tiny pulses are generally 3 per revolution, or about 1.65 Hz, far below being audible in the sub sonic range.
A well-designed direct drive motor, which I assume is the one discussed here, would be incapable of producing "vibrations" to mar the music, as opposed to the higher speed belt drive motors would.
Those types most definitely need some form of isolation, spinning at 300-600 RPM.
Of note here, the DD pulses upon startup are stronger in order to get the platter "up to speed", then reduce in intensity once the feedback/servo system senses the correct RPMs.
There have been many discussions about "cogging" of DD systems, all are rubbish, generated by obsessed and paranoid individuals with no background or technical education of these types of systems.
I've seen it to the point where it confuses the public, and creates an internet-driven hysteria.
Having serviced literally thousands of turntables of all sorts over the past 45 years, I pretty much know what I'm talking about by now.
Thank you for this. I also suspect the MS motor is very good and unlikely to transmit much noise. Certainly compared to a cheap direct drive motor or any belt-drive motor (no matter the quality, given how fast it spins).
But what I don't know is whether what relatively little noise it may transmit is of any concern when it comes to the tonearm. And... if the motor in this case isn't transmitting harmful noise then is there something else within or affixed to the plinth that is and thus necessitates damping? Or is the damping more a matter of addressing interference from external sources?
I appreciate this perspective. Of course, being new to this there are so many perspectives to sort through. Soon enough, I'll start digging in and learning for myself.
But back to my original premise - which is not to attempt to build the perfect plinth, but rather to improve upon the original design. What I'm hoping to find is a simple principle or two to apply. The original build is three layers of chipboard glued together 40 years ago in a production-focused environment. I have to believe that if there was one technician at Micro Seiki, for example, that wanted to build a one-off on the side where production efficiency was of less concern and more attention could be given, that they would have been able to something more refined. And of course, there are material and design innovations that have occurred since then.
So maybe another way to look at it like this: "If the original designers had the benefits of today's knowledge and materials, and were to go back and build a plinth in the same spirit as the original, what might they do differently?"
I just want a solid place to start from given the components I have on hand, which were described in the original post. And that will give me a good launching point to gain some hands on experience of my own.
The motor for the DD-8 is the JVC MC936B2. It's quartz-locked. And not coreless. It has a starting torque of 1.5kg/cm. The 4.5kg platter (from a DDL-120 and driven in that table by a motor with the same starting torque) has an internal mass of 1000kg/cm2. I wish I knew more, but info on Micro Seiki tables is rally hard to find.
Is this at all helpful?
You've got a heavy 10 pound platter, plus the weight of the motor itself.
From my point of view, you don't have a thing to worry about, concerning any vibrations from that.
So concentrate on building a sturdy base, and bolt that sucker and the tonearm down on it.