A GREAT INVENTION.

Waikato Times, Volume 100, Issue 16815, 5 June 1926, Page 5

A GREAT INVENTION.

HAMILTONIAN'S SUCCESS. BOWDEN SUPERHETERODYNE. The following' extracts from a letter received from Mr Bert Howdcn, who is In America, show that the former Hamiltonian is likely to make a name for himself as an inventor. lie writes:— “The phonograph business has been practically smashed in this country by the radio, and in order to survive, a number of firms, notably Victor and Brunswir.k, have appeared with new machines and a new method of recording music. I recently hoard the new Brunswick, which uses radio methods of reproduction. It is far superior to anything of the kind brought out heretofore, and in many respects beats the Edison. It will reproduce a brass band with all the volume of a real band, every Instrument being heard, even to the bass drum. The price is 600 dollars in America. There is. however, an instrument in America which will reproduce a full band with even greater realiism, greater volume and superior tone, and that is the ‘Howden Superheterodyne,’ designed and built by your worthy brother. This is not only my opinion, but has been admitted by the engineers of the Western Electric Company, who are recognised as the greatest experts on sound transmission in the world. The Western Electric Company has nothing to do with the Great Western Power Company. The Western Electric Company is a subsidiary of the Bell Telephone Company, and they have designed and built all of the equipment used in big broadcasting stations throughout America, and have supplied equipment to many foreign lands besides. When these experts pay me a personal visit, to inspect my instrument, and proclaim it to be superior to anything of the kind yet produced, you can bet your boots that I must have produced something very much out of the ordinary, because the ears of gentlemen such as sound transmission experts are no ordinary ears, but are ears that are critical to the last degree through years of training and experience. A Wonderful Instrument. “Since completing the first machine for the people I am staying with, I have built a number of others for different people in the district, and the advertising I have gained as a result has lead to so many orders that I cannot even begin to fill the demand; in fact I am seriously considering the possibility of devoting my entire time to the work. The cost of each machine installed in the customer’s house is £7O to £IOO, depending on the type of cabinet furnished. Of course ready-made sets can be purchased from £2O up, but the majority sound like a fifteen-shilling gramophone. My instrument reproduces not only bands and orchestras exactly as they sound when listening to the actual performers, but it reproduces perfectly the pipe-organ, so that the instrument sounds as if it were built in the house. The thunder of the low notes is such that ybii can feel the floor vibrating under your feet, yet the lone is so perfect and the sound so perfectly distributed around the room that there is no unpleasant effect upon the ears. In the case of a band, the j beating of the bass drum is perfectly reproduced. “Before I became interested in radio I had purchased a large Edison phonograph, the finest musical instrument j of its kind then available. All the radio instruments I had heard up to that time were an abomination before Ihe Lord, and no comparison whatever with the Edison; in fact you would have had to pay me £5 a night lo lolerate one of them in the house. However, I- became interested in the subject, and one day the folk with j whom I stay suggested that I build one as an experiment, to sec if they could not be improved upon. As they agreed to put up the money I saw no reason why I should not give it a go. The years spent in the study of electricity gave me a good foundation lo start on, and it was not long, therefore, before I had acquired a good working knowledge of the subject, 1 and with the acquisition of this knowledge I began to sec wherein lay the weakness in many of the ready-made sets then available. I little dreamed at that time, however, of the brilliant success which was later to crown my efforts, in fact not by the wildest stretch of the imagination could I have conceived the extraordinary and truly revolutionary results which I am now getting. Response to Sound Frequencies. “The human ear is capable of response to sound frequencies ranging from 16 cycles per second to over 10,000. The lowest note on the pipeorgan has a sound frequency of about, 16 vibrations per second, whilst a good example of 10.000 vibrations per second is the note of the E string at the highest position on a violin. Of course there are multiples of these fundamental frequencies called harmonies or overtones, all of which must bo reproduced without any change in their characteristics if perfect reproduction is to be had. The reason you do not hear the bass drum in a phonograph is because, in the first place, recording methods up to the present have been incapable of response to any sounds lower than one octave below middle C, whereas the bass drum note is around 50 cycles. Even if it. were recorded on the record the phonograph could not reproduce it because of the inability of' the small daphragm with which phonographs are equipped. It is for this reason that a band selection or orchestral selection on a phonograph sounds so thin and unlike the real thing. Ail of the instruments producing the lowpitebed sounds, such as the tuba, bass viol, bass horns, drams, etc., do not sound in your phonograph at all, because, as stated, the Instrument is totally incapable of response to them. Tlie same remarks, of course apply to tlie radio. One of the first tilings, therefore, which I had to ascertain was whether the broadcasting stations , were covering the entire musical range audible io the human ear in their transmissions. The chief cn- , pincers in the principal stations as- f sured me lhat. they were. The next | slep was to find out how to pick up, ( amplify and reproduce, these sounds without destroying their character in ] the process. I saw at once that the ( usual loud speaking horn used with commercial sets would not do. These horns are the same as the horns which we used to see on Ihe old type phono -

graphs. They arc usually a swannecked affair with a small diaphragm of about, lliroe inches in diameter at the small end, and they sound about, the same ns a phonograph. The average set on Ihe market employs this means lo make llm electrical sound waves audible, with results, of rourse, as already described in my remarks on the. phonograph. Thus Ihe horn, as a means of reproducing music, was early discarded in my experiments. In my sol I use a large parchment cone with Ihe, apex pointing outward, and this is cemented lo n second cone at Its edge, the apex of the seoond cone pointing in the oppo-,

site direction. The actuating mechanism is in the centre between the two cones, being connected at tlie apex of the front cone by a steel wire or needle. The cones are each 36in. in diameter, and tlie sound waves are thrown off their entire surface boih backward and forward, thus the sound waves are thrown off in every' direc- , tion at once, flooding the entire room simultaneously. Owing to the large diameter of these cones they will respond perfectly to the bass notes, reI producing perfectly the beat of the 1 drum, the double bass, and the lowest notes of the pipe organ, whilst their conical shape causes them to respond equally well to the very high pitched notes, in fact the response of this device is so perfect that it will reproduce the beating of a drum, the lowest note, of the pipe organ, all t.hr sounds around the middle register and the highest notes which can he produced on the violin, all at the same time, without mixing any of them tip or allowing these widely diverging sounds to interfere with each other. First Experiments. "My first experiments with this device were somewhat disappointing. I did not get the bass notes, and the entire performance left much to be desired in every way. I sat up night after night experimenting, in many cases staying up all night until daybreak. I was pretty sure that the reproducer was not to blame, hut that. Ihe radio set itself was eithe.r not picking the bass notes up or was choking them hack somewhere in the amplifying stages. After an endless number of experiments, extending ' over many weeks, in which my ears became sore through continual wearing of a set of head ’phones. I eventually found out wherein my trouble lay.' It was in a part of the equipment called tlie audio transformers. I had the highest grade transformers that money could buy, costing £2 each, and there, are two of them. My tests showed them to be mechanically and electrically O.IC. I soon found out that it was not possible to get any transformers at any price which would amplify every note of the musical scale evenly. They would amplify perfectly around the middle register, but would entirely cut off the extremes of the musical scale. I soon found out that this was an inherent characteristic of all transformers regardless of price. Up to this point I had established the fact that the vacuum tubes in the set would pass the entire band of sound frequencies perfectly without altering their character in any way. It was, therefore, at once apparent that the only solution of the trouble was to do away with the transformers entirely. Had I made that suggestion to any radio engineer lie would have called me crazy. Well, I took the transformers out. I plugged my ear 'phones on to that vacuum i lube called the detector, and I at once noted music of remarkable purity with all the bass sounds present but only just audible in the ear 'phones, and when I took the ’phones off and connected up the loud speaker I found that there was not enough power to make it sound at all. I then increased the battery power, and finally got the loud speaker to sound, but oh, my! what a horrible conglomeration of noises! Plugging my ear ’phones into the detector circuit again, tlie same abominable condition was still apparent. At this point an investigation seemed in order. Connecling a millammeter (a milliamp is one millionth of an ampere) in the grid circuit of my detector. I found that on increasing the power input to the detector I was getting grid voltage swings of the order of 25 volts, with seven volts of the positive peak bei ing cut off and insufficient curren! being fed to the plate at the negative end of the swing. No wonder I was getting noise instead of music. Under normal conditions the detector plate current should not exceed one million) p, whereas under the conditions outlined I was passing no less than I 15, practically paralysing detector ac- ; tion altogether. Reducing flic input to the detector until normal plate current was restored, the music again became beautifully clear and natural, but insufficiently powerful to operate anything but the extremely sensitive head 'phones, it struck me that if I ; could find some means of stabilising the grid of tiio detector so that its response would ho unaffected by large amounts of power delivered from the radio frequency end of Ihe circuit, I lie problem before me would be completely solved. The success, therefore, which eventually crowned my efforts is tiiq direct result of the solution of the problem described. Success at Last. “N'o words at my command could possibly hope to convey to you an adequate description of this wonderful instrument, which, without any outside antennae, reproduces perfectly an orchestra or hand playing in Denver, Colorado, twelve hundred miles away. Portland, Seattle, Salt Lake City, San Francisco, Oakland, Los Angeles, Pasadena, are some of the places we hear. The original set I built required a storage battery of 75 cells to deliver 150 volts to tlie plate circuits. The reproduction of a full orchestra requires a considerable amount of power. One of the latest sets which I have just completed requires only a very small sixvolt storage battery to heat the filaments in the tubes, the plate current being drawn from the lighting circuit. In order to use current from the lighting circuit it must first b.e raised from 110 volts to 350 volts; it must then be changed from alternating to direct current by a suitable rectifier. After it passes out of the rectifier it is direct current all right, hut is pulsating in character. This, of course, would never do, so it must bo ironed out, so to speak. This ironing out process is accomplished by passing it through a suitable filter circuit, which consists j of retardation coils, condensers, etc. , Eventually from an alternating current you can produce an absolutely smooth . and uniform direct rurrenl exactly ' similar to that, which would bn sup- " plied by a storage battery. I built ' one of these rectifier filters to go with 1 a radio set which I have just com- 1 pleted for some people in Antioch. I 1 am making some additional experi- 1 ments with a view to doing away with ' batteries entirely. Up io the present 1 time I have only succeeded in supplying the plate current from Ihe light- < ing circuit, and any attempt to supply < Ihe filament, current from, this source ; has met with failure. However, l am i quite confident of ultimate success. !

“Ami finis ends Ihe slory of the now famous ‘llowden Superheterodyne.’ ’’