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In the Forum: Analog Playback
In the Thread: Copper Mat on a Micro Seiki Gun Metal Platter
Post Subject: That is very nice.Posted by Romy the Cat on: 10/7/2015
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 Wellington wrote:
Perhaps the best test is to play well-recorded piano which runs up and down the scales. Notes exciting resonances may sound slightly louder, with more smearing and sustain. When resonances are vanquished, the music flows with more ease and naturalness, all music, not only piano. Of course resonance control is valid for more than just platters - tonearms, cartridges, speakers and rooms matter too.

It might be a valuable test but in most of the instances the “slightly louder” in this case would be a fraction DB that is not easy to get. There is “simpler” test but it would require to do recording as the test hardly exist in normal music. Take any key on a VERY good piano with no damper or with holding the key. Do it for let say 60 second and observe the wobbling of tone as it will be decaying. Not any piano would do it as most of them do wobble a lot. However, if you get access to a VERY good piano or allocate in your piano a key/note that happen does not wobble then record it, put in on LP somehow and you will have a VERY good tool to test anything you imagine. Do not use for this purpose a recording of decaying generator. You would need a complex cultural note, not just a fundamental pitch.
 Wellington wrote:
Lately I have been playing with a sandwich. First the CU-180 is placed on the platter, then the Fulton mat (or a Micro Seiki leather mat) is placed on top of the CU-180 (minding the VTA adjustments). I have also experimented with the record sitting directly on the CU-180, and weighted down by the 1kg Micro Seiki ST-10 gun metal disc stabilizer . This weight forces the LP to sit on the copper mat’s surface tightly, with no air gaps that could cause buzzing or unchecked resonances. I have not yet formed hard conclusions about which configuration I prefer sound-wise, but I’m leaning toward the CU-180 without any compliant mat at all, in terms of pace and rhythm. One risk of any rubber mat or other compliant mat is that its top surface can shift in the shear mode relative to its bottom surface (without actually sliding) as stylus drag changes with groove modulation. Thus speed is thus slightly modulated by groove modulation, more like in a light platter table. I believe that if the record is held tightly and directly against the heavy platter surface with its high inertial momentum, the speed is less perturbed. More listening needed.

Very interesting indeed. I never played with it as I had only bronze platter on my 5000s.
 Wellington wrote:
Chapter Two: Recently I had machinist Mirko Djordjevik make me a new 5000 platter out of 316L stainless steel. As most of you know, the platters on the last mega tables from Micro Seiki were made from stainless steel. The exterior dimensions and appearance are the same as the original 5000, but I had him bevel the inside edge of the peripheral ring to reduce the cantilevering compliance, and also we thickened the horizontal deck (just below the groove area). Mass went from about 16kg in the gunmetal platter to about 22.4kg in the new stainless platter. That’s roughly going from 36 to 49 pounds. We both believe that the spindle bearing can handle the higher mass. The new platter is a beautiful thing to behold, and tarnishing will no longer be a concern. The only resonance I could pick up was a well-damped one at 1667 Hz, which is about one octave higher than in the original platter, but lower in magnitude with little sustain. With the CU-180 on top, even that resonance was squelched entirely, and once again the sandwich is quite quiet. I have yet to spend time auditioning the new platter. 

Hm, if I had someone to make me a custom platter then I would probably go for curved platter, or a platter that has not plat but parabolic top surface with lockable center weight. This way a record would be kind of indented into the platter with a center let say one inch lower than the peripheral. Then I would set the azimuth of the arm (not needle) with a little angle (to be perpendicular to the record) and run an arm with no anti skating. The presumption is that mass of the arm that will be “continue falling” to the middle or the record should theoretically balance out the circumference force of the needle. How it would be in practice only God knows…
 

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