AEC London Series
London’s Unique Position in Pick-Up Design
The much abused word ‘unique’ can quite fairly be used to describe the production of the Decca range of ffss pick-up heads. No other major record company has devoted so much of its research time to the design and production of high fidelity pick-ups. The reason for this is obvious when one considers the background of The Decca Record Company; in order to maintain its lead with records and recording it has always been essential for Decca to have not only the finest pick-ups of today, but also to investigate pick-ups of the future. The pick-up head is the tool of the recording engineer, and it is generally recognised that the gramophone record is usually in advance of commercially produced equipment with which to play it. To ensure its own future as a major record company Decca is continuously engaged in major research, and for this purpose advanced designs of pick-up head are essential. The transducers produced by the Designs Department for engineers of the Record Company are then manufactured with the same care and meticulous precision so that the full advantages of the advances in recording technique can be made available to the public.
Leading reviewers have often expressed their amazement at the cleanness and transparency of the reproduced sound from the ffss range of heads although, by certain measurements, they may appear to be inferior in some respects to other cartridges.
Whilst engineers are loath to admit the fact, it would appear that the recognized methods of measuring the performance of pick-up performance of pick-up heads or cartridges, although important, are not so conclusive as the test for which a cartridge is really intended: convert into electrical energy movements of the stylus created by the groove. In the majority of cartridges the movement of the stylus following the groove is transmitted by a cantilever which is pivoted somewhere along its length. This pivot usually consists of a piece of rubber or some similar material which has the dual purpose of being the pivot for the cantilever and at the same time acting as a damping medium. Unfortunately, these requirements tend to conflict: in order to provide adequate damping for the stylus system the properties of rubber or a similar material are needed; yet if the rear part of the stylus is to have exactly the same motion as the front, without fore and aft movement, the last type of material one would choose as a picot would be rubber. Precisely because it is an effective damping agent, rubber does not permit the accurate transmission of movement. One can imagine the accuracy of a chemical balance designed in a similar manner, yet the pick-up head is expected accurately to measure movements the amplitude of which approaches the wavelength of light. The moving part of the Decca ffss system utilises a unique method for converting the signal. The stylus assembly is so designed as to require the restraining force of a tie-back thread. As this force is against the direction of travel of the record, the possibility of fore and aft movement is eliminated. (See figures A and B.) The record groove movement is traced by the diamond and the signal produced is measured precisely at the stylus point by the coils which are directly above it. The superiority of such a system is immediately apparent. This general principle, which we have called “Positive Scanning”, is used in the entire range of ffss pick-up heads.
London Head Replacement System
Many heads and cartridges made by other manufacturers offer the user an easy stylus replacement system, and some people feel that it is a great disadvantage to have to return a pick-up when the stylus requires replacement. It must be appreciated, however, that if one is to enjoy the best results, especially from stereo, laboratory precision in stylus location is essential.
The stylus assembly in Decca ffss heads is put together under a microscope and its design is such that, once assembled the stylus cannot move from its correct location. Such desirable precision would be impossible if the user were able to replace the stylus.
But a further positive benefit accrues from returning ffss heads for stylus replacement. This is the Decca Rapid Head Replacement System, which enables the user to have the advantages of a head in which not just the stylus but every component has been checked, and which has a performance guaranteed equal to a new cartridge for the cost only of a replacement stylus.The advantages of buying one of the ffss range of pick-ups can, therefore, be summarized as follows:–
- It has been designed by the organisation which is acknowledged to lead the world in recording technique.
- In order to ensure accurate tracing of such advanced records, a unique transducing system — Positive Scanning — was developed to ‘read’ the minute modulations of the groove and convert them into electrical energy without the intervention of any further mechanical means of transmission.
- It has been manufactured by one of the foremost instrument makers in the country, and is, in fact, a precision tool.
- It is because of its design one of the most stable pick-ups in the world, and its standard of performance will remain constant.
- When the stylus is replaced, the performance is that of a new pick-up.