SOMETHING NEW

Sun (Auckland), Volume II, Issue 433, 15 August 1928, Page 6

SOMETHING NEW

LATEST IN RECEIVERS Despite the oft-repeated assertion that there is nothing new under the sun, Radio, Ltd., has just completed a new radio set that is likely to cause a stir among listeners. It is a fourvalve screened-grid set built in shielded compartments and with one illuminated dial control. It is built for use on all stations from 20 to 500 metres wave-length, and under test has given remarkable results. New Zealand and Australian stations are received with wonderful clarity and volume, while the short-wave stations are as easily picked up as are New Zealand ones. On a set in use in the city Holland and American short-wave stations were heard at such great volume that it had to be reduced. The set so far as appearance is converned is also a novelty, as the cabinet is all metal and it is Duco finished. It has not yet been christened, and next week I hope to be able to make an interesting announcement regarding a name for this new set. I hope to test this set personally very shortly, and will then detail results.

BIAS BATTERY

The bias or C battery consists of a small dry cell, which is connected in the grid filament circuit of the amplifier valve or valves. The object of this battery is twofold. Firstly, it causes the valve to operate on the straight portion of its characteristic curve, thereby eliminating distortion due to grid current, etc. Secondly, it effects considerable saving in the high tension battery in that less current is used. This will in no way lessen the sound in the loud speaker, as it is not the actual amount of current which produces the sound, but the variation of that current. The amount

of bias varies with the amount of high-tension voltage applied to the valve, and also with the type of valve used. It varies from 1£ volts to 40 volts. The reader is advised to carefully follow the instructions issued with the particular valve he has purchased. The diagram shows the correct method of connecting up a bias battery to a receiver. It will be observed that the positive terminal of the bias battery is connected to the negative filament terminal, the negative bias terminal being joined to the filament terminal of the transformer. These same rules apply in the event of two amplifier valves being used, th*? only extra connection being from the F terminal of the second transformer to the negative terminal of the bias battery.

MAGNAVOX DYNAMICS

The definite trend toward power reception which makes dynamic reproduction necessary if the richer, fuller tones on volume which power reception makes possible are to be retained, and recreated into audible sound, brings prominently to the fore the advantages of the magnavox dynamic speakers. Power reception demands dynamics for faithful reproduction over the full range of frequencies, and which is quite impossible to acquire with the average loudspeaker. Magnavox dynamics make any set better. Not only do they provide greater volume but also ‘‘separation” of tones and instrumental values on volume. Magnavox performance pleases the most sensitive ear. Spedding, Ltd., who have just landed a variety of models of these speakers, anticipate a large demand for them.