It consists of a Rek-O-Kut Model V 16" turntable, which he found in the USA (where else?) as a non-runner. The motor was in bad shape and refused to run at all. Even if it would run, it was expecting to be fed on a regular diet of 110 VAC/60 Hz!
The best finds always pop up in the summer, when everyone else is on holidays! Still, they are not always nearby or easy to deal with. When this 1954 Hardinge HLV precision toolroom lathe appeared on the horizon, it took all of 5 minutes to decide to go for it and one week of frantic international phone calls to organize everything. An engineer was sent to check it over, local transportation to an industrial machinery crating facility, international transportation, more local transportation and another week later it was finally in our yard!
The Type 6079 is our new low profile record clamp, for securely holding the blank disk in place on a disk recording lathe, during the cutting operation.
A customer recently imported a vintage Presto 75A disk recording lathe from the USA, with a view to cutting records in Europe.
He quickly discovered, like many people before him, that it was spinning a bit slower than it should, when operated from 50 Hz mains, via a simple step-down transformer. As with most vintage record cutting machines, the platter is powered by a synchronous AC motor, which "locks" to the line frequency.
Following up on the progress of the restoration work on a vintage Presto disk recording lathe and the Agnew Analog Reference Instruments Type 6021 Toolpost with integrated oil dashpot, as described in our previous episode, we are now presenting the complete suspension assembly.
A rather optimistic gentleman arrived with a Presto MRC-16 disk recording lathe, inquiring about the possibility of repairing the broken suspension and making a cutter head bracket from scratch. He then asked about the possibility of figuring out some way in which lead-in, lead-out, and track mark spirals could be cut on this machine, which was originally intended as a very basic machine, with no provision for spirals, not even a hand crank. Then came the really ambitious part: He would ideally like to be able to adjust the pitch and if possible, control the lathe through his computer!
One glance at the steampunk aesthetic of the manufacturer's name plate and the overall state of this primitive machine would have been enough to deter the average engineer, in fear that there might be something potentially radioactive hiding within...
In 2015, J. I. Agnew started developing a high-end cutting amplifier for disk mastering systems, to be used with motional feedback stereophonic cutter heads. During this process, he investigated the design and implementation problems of such transducers in great detail. As usual, he documented his progress, which evolved into an engineering report, titled "An Investigation of Motional Feedback Disk Recording System Design", which was accepted for publication in the November 2018 issue of the Journal of the Audio Engineering Society, following the customary peer review process.
Happy new year! Time to reveal what has been secretly developing in the lab throughout the past year: A stereophonic cutter head of an entirely unique design, invented by J. I. Agnew during his work with experimental transducers for measurement and testing purposes.
There is a long history of use of precious stones as industrial materials, from precision bearings to cutting tools, lapping compounds to grinding tools and several other specialised applications.
The recording of phonograph records is essentially a machining operation, performed by means of a machine tool called a disk recording lathe. A special cutting tool is used to cut a continuous spiral groove on the surface of a blank disk. This tool is called a disk recording stylus, or simply cutting stylus.
The big difference to other forms of machining is that there is sonic information stored as modulation of the cut groove, which can be reproduced on another special machine, often called turntable or record player, or disk reproduction system.
In the previous episode, we had a look at taper shank stylus adapters and saw a vintage magnetic monophonic cutter head fitted to the AM44 lathe. The two are not normally compatible. Neumann lathe suspensions do not have the same mount as the suspensions of Presto, Fairchild, RCA and other lathes of the monophonic era, which were originally designed to accept such cutter heads.
But, in fact, almost any cutter head can be fitted to any lathe, as long as there is enough space for it to physically fit, by means of a suitable adapter. The eagle-eyed reader will probably have noticed that the cutter head mount on our prototype AM44 suspension is similar to, but not the same as, the mount used in Neumann suspension boxes. So, the adapter shown here was made specifically for our AM44 suspension unit.
Stereophonic cutter heads developed by Neumann are designed to accept a cutting stylus with a conical shank, resembling a micro-miniature version of a Morse Taper, a type of fitting frequently encountered in machine tools, especially metalworking lathes. Vinylium and FloKaSon cutter heads also adopted the same fitting for the sake of compatibility. But most other cutter heads, especially all those predating the stereophonic era, used long, thin cylindrical shanks, often with a flat machined on one side, to allow a set-screw to align the stylus and secure it in place.
Back in 2015, we started a big lathe project, taking a beat-up Fairchild lathe from the 1930's, fitting it with an RCA cutter head, and eventually going full-on with a stereophonic feedback cutter head, vacuum clamp-down platter and automatically variable pitch.