With GRAMOPHONE and RADIO

Radio Record, Volume III, Issue 31, 14 February 1930, Page 32

With GRAMOPHONE and RADIO

BY

B NATURAL

The Technique of the Pick-up, | the Reproducer and the Record

‘ey ease the word "technique" in the title might frighten some of our readers who wish to know a little more than that necessary to turn a switch and change a record, let me say from the onset that this is not a technical talk, but one that proposes to delve just sufficiently below the surface to impart to readers information that will be vital if they wish to obtain the best results from their combination. We all know that the modern instrument is simplified to a degree that renders superfluous a knowledge of anything but the simple operations necessary to playing the combination, but there -is still a very large number of music-lovers who have a separate pickup in combination with their radio receiver. In these cases such considerations as the adjustment of the pick-up and the amplifier of vital importance and our chat this week will be largely devoted to cases that fall under this heading. But the owner of the commercial combination must not feel that for this week, at least, he is left out of the question, There are very many rules of thumb that he must observe if he wants his records to last well, and if he will obtain a superficial knowledge of their construction he will keep his records in a better state than knowing nothing he does no more than to follow common sense, which may or may not be good sense. S°: having introduced our subject to all, let us look for a few moments at the pick-up itself. Wherein does it differ from the head of the gramophone? A pick-up is almost the reverse to a speaker. The vibration imparted to the needle causes it to move between two magnets around which are coils of wire connected to the amplifier. The needle in moving causes a fiuctuation in the lines of force surrounding it, and this is transferred down the wire to the amplifier, where the weak impulses are strengthened up and sent to the speaker, which reverses the proceedings and transforms the electrical vibrations into movements in the air which we call sound. ‘And that is the "technique" of the pick-up; simple is it not? The ordinary gramophone reproducer transforms the mechanical movement of the needle to movement of the tight diaphragm which moves the air. The moving is audible if the ear is close enough. To amplify the sound it is sent down a long passage and due to the shape of this the sounds are strengthened. The magnets of the pick-up are very much more sensitive than is the diaphragm, so that tones and overtones, impossible with the ordinary gramophone, are quite everyday occurrences with the pick-up and

the amplifier. This makes possibile greater quality and volume-it imparts realism. _ The Record. To make a record an artist or combination of artists perform very much as though before an audience (bows and encores excepted), and a microphone or microphones are placed in positions that give the best balance when all the impulses are collected. This is much the same procedure as in the broadcasting studio, and as here the sounds collected are amplified, but when a recording is being taken the sounds are passed to an instrument which reverses the action of the pickup and transforms electric movement to movement of the needle, and this impresses a specially prepared wax disc which is revolving at 78 revolutions a second. The sounds result in a horizontal movement of the needle and a groove which varies in width from side to side ismade. It can be seen that the distance between the grooves widens and narrows according to the frequency ‘of the sound; the deeper it is the smaller the distance between them. This is an important point to grasp, as it will be alluded to later when we consider adjustment of the pick-up, needles, and the care of records. Correct Adjustment. For the gramophone enthusiast who adds a pick-up to his receiver we eannot stress too forcibly the necessity to correctly adjust the pick-up both with reference to the angle of the head and the sweep of the arm. If the slope of the head is not correct the grooves of the record do not get a fair chance, as the thicker part of the needle is pressed too close to them and forces them open, with the result that the record loses much of its power of supplying undistorted music to the reproducer. If, too, the sweep of the arm is not correct there is a drag on the grooves on one or the other side with the same result. Adjustment is absolutely necessary, and here the writer must diverge to tell an incident that has come with--in his ken. An enthusiast installed a pick-up ‘without reading the instructions-he trusted to common sense. Everything went well until one or two of the records began repeating suspiciously several bars. The records were wearing badly, and, naturally, the pick-up was blamed for being hard. However, the writer happened to see this apparatus, and-now the records are not wearing out so quickly. Just a few adjustments and quite simple ones, too. It would require too much space here to reiterate what has already

been published in this respect. The writer can do no better than refer those who use a separate pick-up to "All About the All Blectric,’ where this problem is treated very fully. Although we have only skimmed the surface of the subject of technique we have finished, for we wish to give practical talks and not vague theory in this column. Next week we shall deal with the all-important subject of needles. =

radio combinatoin we are devoting this section to gramophone side of the combination. It is hoped to discuss in non-technical language some of the oft-asked questions, "Do pick-ups shorten the life of records?" ‘What type of needles should be used?" ‘How do pick-ups vary?" "Why is the Pick-up superior to the ordinary gramophone?" and a _ host of other interesting and important points that concern the owner and the prospective owner of the combination or the electric gramophone. Further, the most important releases will be reviewed in brief and from time to time short biographies of the better known composers and artists will appear. the growing popularity of the gramophone andty the