Series 6100 Vacuum Platters for Disk Recording
Vacuum platters use vacuum suction to clamp the blank disk down on the platter surface. Apart from holding it securely in place during the cutting process, vacuum suction also serves to flatten the blank disk onto the platter, using the top surface of the platter as a reference. If the top surface of the platter is dead accurate, like the surface on our vacuum platters, then the only errors remaining are those due to the variable thickness of the blank disk. This greatly improves the overall system accuracy and allows the parameters to be adjusted for best sound quality, rather than for the ability to ride out surface irregularities caused by the accumulative errors of the blank disk, platter surface, platter geometry, shaft geometry and bearing unit design and implementation.
The concept is not new, it has been used for many decades by Neumann, Scully and Fairchild disk mastering lathes, as well as in precision metalworking, in workholding devices called "vacuum chucks". A vacuum platter is effectively a vacuum chuck, fitted on a suitable lathe and intended to hold blank records. However, vacuum platters for disk recording lathes must be made from non-ferromagnetic materials, as many cutter heads have significant stray magnetic field and would become violently attracted to a platter made of a ferromagnetic material.
The Agnew Analog Reference Instruments Series 6100 vacuum platters represent the current state of the art in professional disk recording and mastering technology. Machined from an aerospace-grade Aluminum/Magnesium alloy, they are incredibly accurate, offering improved control and consistency of the depth of cut when appropriately installed.
The videos below demonstrate the accuracy and surface finish typical of our new vacuum platters. The first one shows J. I. Agnew indicating the outermost ring of a vacuum platter, still held on our 1961 Moore Special Tools Jig Borer, right after machining, using a Starrett Last Word 0.0005" dial indicator.
The second video shows the same platter, after removing from the machine to wash and placing back on the Jig Borer, with no clamping, to inspect. The inspection involved indicating the outermost ring again, but this time with a Starrett Last Word 0.0001" dial indicator. Each graduation on the dial represents a displacement of the probe tip of 0.0001" (0.0025 mm), and as you can see, the needle does not even move! There has never been a disk recording
lathe platter of any manufacturer and any vintage that could even come close to achieving this level of accuracy (not even Neumann or Scully).
It certainly helps that these platters are machined using a high precision machine tool made by Moore Special Tools of Bridgeport, Connecticut, USA. Just ask the National Institute of Standards and Technology (USA), the National Physical Laboratory (UK), or the Bureau International des Poids et Mesures (France) about them.
Or visit any well funded metrology institute and see for yourself that Moore has pretty much been setting the standard for several decades now. Still, it took us approximately three years of intense research and development effort and several prototypes of different versions, until we finally arrived at the present ultimate version. It took countless hours and several thousands of dollars sunk into machining custom tooling in our own toolroom, which we now use in the manufacturing process for these platters. This tooling contributes to the accuracy achieved, but also enables us to manufacture these platters at a very reasonable cost.
As is always our aim, with the Type 6112 and Type 6114 Reference Instruments, we are introducing true reference-grade vacuum platters, setting a new standard for accuracy in the manufacturing of vinyl records, which can be augmented further with the Type 612 disk mastering lathe. The accuracy advantage can be leveraged to further improve upon the sound quality achievable on our favorite medium!
These vacuum platters were developed for use with the Agnew Analog Reference Instrument Type 612 disk mastering lathe, but can be and have been fitted to various other lathes, using our custom sub-platters, shafts and bearing units. Vintage Scully lathes, Neumann lathes, Presto, Fairchild, Rek-O-Kut, RCA and various other lathes can be converted to use our vacuum platters, and also converted to direct-drive, using our Type 631 or Type 632 direct-drive motors.
Our vacuum platters can also be installed on top of any existing turntable platter, converting your vintage lathe or turntable patter to a vacuum type at a very modest investment.
We are currently offering 12" and 14" versions of our vacuum platters. Both can be used to cut 14" lacquer master disks. The 14" version is considerably more expensive, due to the additional material and the added difficulty in manufacturing it to such a degree of accuracy. For most purposes, we recommend the 12" version. If you would like a 16" version, or a 7" version, we can make these as a special order. The Type 6112 is the 12" version and the Type 6114 is the 14" version. We are happy to supply the vacuum platters on their own for your project, and we are also happy to supply anyone interested in restoring, or modifying, or building lathes, for personal use or for commercial purposes.
We can also supply sub-platter assemblies, adjusters for levelling the vacuum platters, spindles of unusual design, vacuum fittings, vacuum pumps and custom parts to enable the successful mounting of our vacuum platters on any lathe.
If you would be interested in purchasing a large number of our vacuum platters for use with a new product, we would be glad to help. Please feel free to contact us.