Some time ago we were asked to repair a vintage Westrex 2B feedback cutter head.
As with all Western Electric and Westrex products, their cutter heads were beautifully made and represented the state of the art in their time. Not only did they sound great, they also looked aesthetically pleasing, with curved lines that were not a trivial task to manufacture, in the days before CNC machine tools, CAD software and pocket calculators!
A good machine spindle is one of the factors defining the accuracy attainable from rotating machinery. This applies equally to machine tools used in industrial manufacturing and to disk recording and mastering lathes, used to make phonograph records.
At Agnew Analog Reference Instruments, we use some of the finest and most accurate industrial manufacturing machine tools ever made, to build some of the finest and most accurate disk recording and mastering equipment ever made, so we have had to learn a thing or three about machine spindles along the way.
For many long years, J. I. Agnew has been examining, adjusting, repairing and replacing bearing systems of all kinds, from disk recording lathes and turntables to tape machines, high precision machine tools, measurement instruments, industrial equipment and all manners of motor vehicles, from passenger cars to heavy trucks. Over the past few years, he has designed and machined countless bearing units to replace worn or damaged units on a diverse range of disk recording lathes and machine tools. Valuable experience was gained, which along with his solid engineering background, was put to good use in improving his designs further and further, up until the current stage of development was reached.
The ultimate vacuum platter is finally here, and it is very reasonably priced. After three years of exhaustive research and development and several prototypes of different versions, along with field testing, we have finally arrived at what we believe is the most advanced and accurate vacuum platter ever made.
The Agnew Analog Reference Instrument Type 192 is a minimalist, industrial-grade stylus heater supply unit, designed and built to last forever.
It is a current-regulated design, set at the factory for 550 mA, in an ultra-ruggedized configuration, for maximum reliability in constant-duty environments, when downtime is not an option.
The Fairchild line of disk recording lathes, first appearing in the early 1930’s, featured a General Electric hysteresis synchronous AC motor, running at high speed, with a worm and gear reduction to drive the platter. While this system in its various permutations in their different models was impressively well made and performed well for its time (see here for a more detailed description and pictures), a direct-drive system with a floor mounted motor is clearly the way to go if the highest level of performance is to be attained.
Our popular Agnew Analog Reference Instrument Type 1501 Stylus shank adapter was intended to make it possible to use the Neumann-style taper shank stylus (Transco 320, Adamant NSH-2, etc) with vintage mono heads such as the Presto 1-C and 1-D, which need a long shank stylus.
Up to now, customers would just install the adapter and leave it there, only occasionally replacing the stylus. One customer, however, wanted to be able to leave the stylii aligned in the adapter, and change them out without needing to realign.
Neumann cutter heads have a rib along the back, for mounting. Presto lathes, on the other hand, together with the vast majority of non-Neumann vintage lathes (Rek-O-Kut, Fairchild, etc.), have a mount with two slots, for cutter heads with two threaded holes on the back (Audax, Presto, Fairchild, RCA, etc).
Sabine Agnew was recently interviewed for "Women in Vinyl", a publication featuring women professionally involved in vinyl record manufacturing and other fields related to the vinyl industry.
Read the interview here: Women in Vinyl
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 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.
It would appear that 50 Hz conversions of vintage "made in USA" disk recording lathes are becoming rather fashionable! Last week we examined how we converted a Rek-O-Kut Model V by machining a new capstan and making a special transformer, Type 1760.
We have done 50 Hz conversions (and even some 60 Hz ones!) on many different lathes and turntables, using all of the possible methods of doing so: New rubber rollers, new capstans, new belt pulleys and even electronic frequency conversion (Agnew Analog Type 191 frequency converter) for professional disk mastering systems.
This week, we will have a look at the Presto 75A, a high quality machine, dating from the 1930's, which was even used by the BBC as a broadcasting turntable!
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.
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.
