Once Analog Posted March 8, 2014 Posted March 8, 2014 Mass A reasonably heavy platter is generally preferred in the turntable industry with a mass in the order of 4kg. The main advantage of a massive platter is its intrinsically high angular momentum (similar to inertia) which tends to reduce wow and flutter by smoothing out small variations in the drive system. Distribution of mass The amount of mass that can be utilised in a design has a practical upper limit due to the extra burden a very heavy platter would place on the mechanical system. The physics of rotating bodies affords us a convenient method of reducing the overall mass of the platter whilst retaining the benefits of the higher momentum. It turns out that the mass that is distributed furthest from the centre of rotation has the greatest contribution to the momentum of the system. Therefore cutaways towards the middle of the body of the platter are often employed. Platter mat A layer of isolation from any residual noise, vibration or resonance artefacts in the mechanical system can be achieved using an appropriately designed turntable mat. OA
Krispy Audio Posted March 8, 2014 Posted March 8, 2014 Is that one of your platters Vince? I'd love to see a vid of it being milled.
Once Analog Posted March 8, 2014 Author Posted March 8, 2014 Is that one of your platters Vince? I'd love to see a vid of it being milled. Yes, the OA platter. OA
cmcook Posted March 8, 2014 Posted March 8, 2014 (edited) Sounds like a job for some topology optimisation targeted to: - Minimise mass - Maximise Inertia (or maintain above a certain level - such as the inertia value of the current platter) - Maximise frequency of first normal mode or maintain above a certain frequency It'll come up with an answer that's a lot harder to make though Edited March 8, 2014 by cmcook
Krispy Audio Posted March 8, 2014 Posted March 8, 2014 Hey Vince here's something I've always wondered. After milling, does the platter need to be balanced then fine tuned, or is the milling accuracy that good these days that it comes out 100%?
Once Analog Posted March 8, 2014 Author Posted March 8, 2014 Hey Vince here's something I've always wondered. After milling, does the platter need to be balanced then fine tuned, or is the milling accuracy that good these days that it comes out 100%? Hi Krispy, Fully machined on an accurate lathe, the platter does not require further balancing. OA
Decky Posted March 9, 2014 Posted March 9, 2014 From the turntable performance perspective you cannot separate platter from the bearing. Any analysis has to include both. Bearing defines the centre of gyration while the whole assembly will define the centre of mass. The starting point is dealing with the issue of these two pints not overlapping. After that comes everything else. Finally you have to include drive mechanism (belt, DD) effects. Designing platter alone in isolation is meaningless. 1
Once Analog Posted March 9, 2014 Author Posted March 9, 2014 From the turntable performance perspective you cannot separate platter from the bearing. Any analysis has to include both. Bearing defines the centre of gyration while the whole assembly will define the centre of mass. The starting point is dealing with the issue of these two pints not overlapping. After that comes everything else. Finally you have to include drive mechanism (belt, DD) effects. Designing platter alone in isolation is meaningless. Regardless of the drive system; Direct Drive , Idler Drive or Belt Driven, platter design is as mentioned above. The many platters inspected, built by renown makers; Sota, Michell, Garrard, Lenco, Dual, Pioneer, Elac and Oracle, (to mention some), follow the above design philosophy. I am away until Tuesday afternoon, no access with my computer. Upon my return will post up some platter pictures, I have many. OA
andyr Posted March 9, 2014 Posted March 9, 2014 Regardless of the drive system; Direct Drive , Idler Drive or Belt Driven, platter design is as mentioned above. The many platters inspected, built by renown makers; Sota, Michell, Garrard, Lenco, Dual, Pioneer, Elac and Oracle, (to mention some), follow the above design philosophy. I am away until Tuesday afternoon, no access with my computer. Upon my return will post up some platter pictures, I have many. OA I'm devastated, Vince - you didn't mention Linn in your list of renowned TT mfrs! Regards, Andy 1
Addicted to music Posted March 9, 2014 Posted March 9, 2014 I'm devastated, Vince - you didn't mention Linn in your list of renowned TT mfrs! Regards, Andy WTF, Linn makes TT????
Once Analog Posted March 11, 2014 Author Posted March 11, 2014 (edited) Regardless of the drive system; Direct Drive , Idler Drive or Belt Driven, platter design is as mentioned above. The many platters inspected, built by renown makers; Sota, Michell, Garrard, Lenco, Dual, Pioneer, Elac and Oracle, (to mention some), follow the above design philosophy. I am away until Tuesday afternoon, no access with my computer. Upon my return will post up some platter pictures, I have many. OA Hi Guys,As promised, here are some pictures showing the underside of various platters. Thorens TD3001 (Belt Driven), Lenco L75 (Idler Drive), Commonwealth (Idler Drive) Garrard 301 (Idler Drive), Michell Gyro Dec (Belt Driven). Please note, the increased mass around the perimeter! (More to follow) OA Edited March 11, 2014 by Once Analog
Once Analog Posted March 11, 2014 Author Posted March 11, 2014 (edited) Trying again up loading pictures. OA Edited March 11, 2014 by Once Analog
Once Analog Posted March 11, 2014 Author Posted March 11, 2014 Roksan Audio, (current), world acclaimed turntable builder. Their Xerxes platter follows the same design principles, as mentioned in my opening post in this thread! Has someone got it wrong?
Once Analog Posted March 11, 2014 Author Posted March 11, 2014 (edited) Many vinyl enthusiasts say the Sota is the most musical turntable ever made! View the attached picture and note the lead inserted platter perimeter!OA Edited March 12, 2014 by Once Analog
Once Analog Posted March 11, 2014 Author Posted March 11, 2014 All pictures attached, taken by yours truly, players from my own collection. OA
Once Analog Posted March 11, 2014 Author Posted March 11, 2014 (edited) Dual 701 and Pioneer PL 71, both Direct Drive, same platter design features as Idler Drive and Belt Driven turntables. OA Edited March 12, 2014 by Once Analog
Once Analog Posted March 12, 2014 Author Posted March 12, 2014 Thorens TD125 Mk 11, (highly regarded). Two piece platter design, partially machined and balanced. Platter weight: 2.970kg. OA
Once Analog Posted March 12, 2014 Author Posted March 12, 2014 (edited) Linn Lp12, two piece platter design, fully machined, (best option). Probably the most controversy record player of all! Platter weight: 3.745kg.OA Edited March 12, 2014 by Once Analog
Once Analog Posted March 12, 2014 Author Posted March 12, 2014 To my knowledge, the only turntable platters that don't follow the design criteria mentioned here, are those made with compromises - built to a price, not a standard! OA
Once Analog Posted March 12, 2014 Author Posted March 12, 2014 Once Analog platter, one piece design, fully machined from 6061-T6 aluminium, (high grade). Platter weight, 3.955kg. OA
lovetube Posted March 12, 2014 Posted March 12, 2014 nice Collection of platters you have there Vince. your look like it is the best out of all . Duc
Once Analog Posted March 13, 2014 Author Posted March 13, 2014 nice Collection of platters you have there Vince. your look like it is the best out of all . Duc Hi Duc, Nice comment, thank you. OA
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