Agnew Analog Reference Instruments Blog
Agnew Analog Blog

Lab Report: An improved cutter head mounting system with integrated dashpot

The need for a new suspension for our recently presented Presto MRC-16 modification project brought about yet another innovation from our R&D laboratory: The Agnew Analog Reference Instrument Type 6021 Lathe Suspension Toolpost!

Inspired by the toolposts used in metalworking lathes and improving upon the cutter head mounting system used by Neumann, the Type 6021 will accurately and rigidly hold any cutter head fitted with a suitable bar, including Neumann, Vinylium and FloKaSon heads, as well as any other head imaginable, through the use of our Series 1400 head mount adapter range.

Presto MRC-16 Variable Pitch Modification

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...

Repairing a Dial Indicator

A simple yet effective movement which has seen many decades of regular use, appears under the lid of this dial indicator.

It was once able to indicate accurately in 0.01 mm graduations, through a gear train driven by a rack on one side of the spindle.

Presto MRC-16 Lathe Motor

Presto disk recording lathes are often still in active use nowadays, nearly 80 years after they originally left the factory in New York. Let us have a closer look at what keeps them spinning!

Accurate Record Reproduction: Thorens TD160, SME 3009 and Van den Hul MC Two

For some reason, the people involved with the manufacturing of vinyl records are rather stoic types. The rare occasion when they are in a talkative mood, they mostly talk about the manufacturing process and equipment. They are not often talking about what happens after the records have been manufactured, the actual reproduction of these records, for pleasure or for the most critical step of manufacturing: Quality control.

Modified Thorens TD160 with SME 3009 and Van den Hul MC Two cartridge, with a test record
Modified Thorens TD160 with SME 3009 and Van den Hul MC Two cartridge, with a test record

What follows is the story of the restoration, modification, assembly, calibration and testing, of some components, which, if used properly, can result in a highly accurate phonograph disk reproduction system.

Motional Feedback Disk Recording System Design

 

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.

Lab Report: The Agnew Analog Stereophonic Cutter Head

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.

Scully Lathe Restoration and Modification

This beauty is a fully restored and extensively modified, vintage Scully lathe, operated by Eric Conn at Independent Mastering, in Nashville, TN.

It started life in the 1940's as a completely manual machine. A sturdy design, capable of very decent results, these lathes were extensively used across the USA and other parts of the world for several decades. Many are still in operation today. In the original condition, they were quite limited in what they could do. But, as with most good lathes, they can take a lot of modification and improvement.

Precious Stones for Cutting Precious Records

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.

Lab Report: Cutter Head Mounting Adapters

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.

Lab Report: Making cutting stylus shank adapters

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.

Critical listening at home: Audiophile High Fidelity Sound Reproducing Systems and the Recording Industry

audiophile analog audio setup

Meet George Vardis, a retired biologist with a Master's Degree in Food Technology, residing in Athens, Greece. George is a sophisticated man with many interests, including sailing, photography, motorbikes, and music. He plays the piano and the guitar, but his career always steered well clear of the music industry. He was never a recording artist, nor was he a recording engineer. In fact, he has probably never seen a recording studio in real life.

Schaublin 102 and Simonet two speed drive unit

Swiss Precision Engineering: The legendary Schaublin 102 precision lathe with parts of a Simonet lathe in the Agnew Analog laboratory! These pictures are from a 2016 restoration project, documented on the Agnew Analog website. Read the full report here: Schaublin 102 Swiss Precision Lathe Restoration

The AM44 Disk Mastering Lathe Project

The AM44 is a Neumann-based lathe, built on original Neumann castings, manufactured around 1944, during the second world war.

The project was founded by Flo Kaufmann, in Switzerland, when he managed to find a pile of these rare beds in the unexplored depth of a warehouse. The plan is to build them up into fully functional disk mastering systems, using newly designed and manufactured parts.

In 2016, Sabine and J. I. Agnew acquired one of these beds, built up and further developed it, into an exceptional quality disk mastering system, which was put to professional service at Magnetic Fidelity.