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In Reply to: RE: Opinions wanted on a DIY turntable project posted by henrybasstardo on December 14, 2014 at 22:50:15
I'm pretty far down a similar path. In my case, I started with the Empire/Rek-O-Kut Papst motor and the bearing/platter from an Empire. Before you get very far along, you should make sure your motor is up-to-spec. On my motor, I could replace the thrust bearing with a new Delrin disk and that made it much smoother and quieter. The Falcon wthetheill let you control the speed by varying the frequency and let you reduce the voltage a bit which often helps vibration (does not actually help with my Papst). It also gives you the option/opportunity to buy the module to speed-monitor and feedback to slowly adjust to keep long-term speed close to spec. But if your chosen motor itself is not quiet, everything else about your design will be compromised. Ask me how I know this....
I'm now on my second motor!
You also need to think about whether the motor is a stand alone SAMA or whether it is mounted somehow in the plinth. I had some conversations with Harry W at VPI who is an Empire enthusiast. He convinced me of the benefits of having the motor quite close to the platter, as was done in the original Empire design. I duplicated that layout on mine, which resulted in a lot of trial & error machining a pocket for the motor of the right size beneath the plinth. It also involved looking a how to suspend it in such a way that vibration would not be transmitted to the plinth. i found a company that makes good suspension/isolation bushings which seem to do the trick for me.
I've also worked through quite a variety of platter and mat designs. But that is another story unto itself. I certainly like a damped aluminum platter better than the acrylic platters I've worked with in some other attempts.
Slate as a plinth material has its pros & cons. I considered it for mine, but ended up with a 3-layer high-mass base, with a 1"thick aluminum plate clamping a sheet of EAR Isodamp to a steel layer of identical mass (about 3/8" thick) which is glued to a damping base of 2.25" MDF). It ends up at about 75 pounds. It is suspended by a frame made of 3" thick Walnut, anchored by 3 Terrastone/brass footers equidistantly spaced around the center of mass. I consider the plinth a little livelier than the slate one I used on my Thorens TD124 project, but still quite quiet. No ringing at all, since the aluminum and steel resonate at different frequencies and are clamped via a superior constrained damping layer, further damped by the MDF.
As far as tonearm choice goes, you might want to think about through-arm mounting vs. Surface mount early in the process. I went the SME mount route, which means that whatever arm I choose has to work with the SME standard. But that also means there's a BFH (Big Frickin' Hole) in my baseplate. I originally fitted an SME 3009-II, but as others here have noted, it is not the last word in performance, especially in the bass. I borrowed an SME 309 and liked it fairly well, but before I bought one of my own, I discovered a cottage manufacturer in the UK who was spinning off the SME design and making his own tonearm with the goofy name: Sonik Sircle. I saw a positive writeup of the arm in a Brit Hi-Fi mag and started a correspondence with the designer. He's an expert on resonance and vibration. He makes a replacement wand for the SME which is damped carbon fiber and for less than $700 I had a really nice-sounding arm that thoroughly thrashed the SME 309, at least on my table. I think I would need to go to at least an SME-V if not a Graham Phantom SME-mount to better its performance.
Anyway, hopefully this will help you, or at least give you some things to think about. I do have full pics of my build process if you want to PM me. Good luck with your project and keep us posted on your progress!
"Knowing what you don't know is, in a sense, omniscience"
Follow Ups:
Thanks for the post. I have a lot to think about for sure. Your post will surely help.
One thing I did find was my motor is too big for the Falcon but the company is coming out with the Eagle that will work for it. I will be back at this after the new year.
Happy Holidays to you and yours.
I'm a big fan of Phoenix Engineering's project. In fact, I was the one who jokingly suggested the name "Eagle" ;) It seems to have taken hold.
My Papst motor pulley is slightly large (or the circumference of the platter is slightly small) so my table runs slightly fast, based on a couple of downloaded smartphone apps for measuring speed. Interestingly, the thickness/width of different belts changes the measured speed significantly in this design (using a double-tapered motor pulley).
My VPI is dead-on 33.3rpm, but the DIY table runs at 34.1rpm. The speed problem is much easier to fix by varying incoming frequency, compared to machining the pulley. That's not to mention the Phoenix advantage of regenerated AC voltage as it improves stability and lack of noise.
I'm looking forward to the higher-power version. What I really *should* do is build a proper 3-phase supply that feeds each of the coils on my motor (it's a 3 phase synchronous eddy-current motor). But the feedback mechanism that Phoenix has developed looks like a superior solution.
Another factor from a motor noise standpoint is the voltage. I've found through experimentation that the Papst actually runs smoother/quieter at faster speeds. Using the Phoenix, I might be better off putting the belt on the 45rpm pulley and using the controller to drop the frequency so I can obtain 33.3rpm at the platter with a higher motor speed. The Papst seems unusual in this. Other motors I've used (Thorens) seem to be quieter with lower voltage. But it is (yet) another thing to focus on.
When designing my table, I broke it down into four areas and worked through each one. So I did development testing on motor mounting and motor noise. I worked on plinth design/layers/damping. I worked on the platter, which needed damping (rang like a bell!). And I worked on alternative tonearms. All told, it took me about a year to arrive at the final table, much of which was spent waiting to get parts out of the machine shop.
Fortunately, I'm very happy with the outcome. One of these days, I'll put my pics together and tell the story here. It was a very rewarding job!
Good luck with your project!
"Knowing what you don't know is, in a sense, omniscience"
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