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.
While the taper shank stylus is more fiddly to install and align, it offers significant advantages in terms of precision in locating and control of resonances. This is the most common disk cutting stylus in use by professional mastering facilities nowadays and they are still manufactured in larger numbers than any other type.
So, what does one do, when they only stock taper shank styli, but are suddenly asked to use a vintage monophonic cutter head, for which they do not actually have a stylus? The taper shank stylus will definitely not fit in there, and it would be uneconomical to purchase a special stylus, which can only be used with the monophonic head, only for a cut or two. This is exactly the situation we found ourselves in, when asked to test a couple of vintage monophonic cutter heads and develop electronics for them, after just having sold our last remaining compatible styli!
We had heard rumours of an adaptor that could fit in a monophonic head, but accept a taper shank stylus on one end. A search yielded no results, not even a hint that such a thing had ever existed. If it ever did exist, it seems like it was made of unobtanium!
But, putting the idea down on paper, there is no reason why such an adapter should not be possible to make, as long as one has precision machine tools, capable of micro-machining tiny parts, at their disposal, is proficient in their use, and understands the fundamental requirements.
So, a few hours later, I had successfully machined the first two prototypes for testing and hardening experiments.
The adapters will accept a Transco 320, Adamant NSH-2, MyShank 320P or 320S, or other Neumann-compatible stylus, and present a shank known as a 468-type, suitable for many monophonic heads, such as the popular Presto 1-C and 1-D.
Some other monophonic heads, notably several models manufactured by RCA, will theoretically accept this adapter, but it will protrude too much.
These heads were designed for a somewhat shorter stylus. Not much of an issue, I just made a couple of shorter adapters as well!
If you are wondering how I fitted a monophonic head to the AM44, stay tuned for the next episode....!
e can of course also make custom adapters for oddball cutter heads, do not hesitate to ask!