Improved Conditions

Radio Record, Volume III, Issue 25, 3 January 1930, Page 12

Improved Conditions

Better Valves and New Transformers POINT that is often lost sight of wher considering the merits of yarious transformers is that present--day valves are, on the whole, much better than those available a year or two ago. The result of this is that, for a certain standard of performance, the transformer need not be such an expensive component as formerly. To explain this point more fully, let us imagine we have a receiver having a transformer-coupled stage that is fitted with a valve whose impedance is 416.000 ohms, for a magnification factor vf 10. We remove this valve and put in a modern one, haying an impedance of 8000 ohms for a magnification factor of 10, which is quite reasonable. Immediately it is noticed that the lower notes are strengthened and _ it mmy so happen that the higher notes are also strengthened in comparison with those of middle frequency. The effect of fitting a new valve in this instance is, therefore, to’ improve the reproduction. If one happened to be satisfied with the reproduction of the old nrrangement it would be possible to fit a new valve having about the stine anode impedance as the old one, but having a greater magnification factor. The overall amplification would, therefore, be increased. It is further possible for one to fit a new valve of lower fmpedance, but the same magnification factor as the ole valve, and also to fit a transformer having the same ratio as the one used at present, but hav! ig less inductance Such a transformer would -be cheaper, because inductance is dependent upon the size°of the iron eore, its, quality and the numbér of turns of wire. Less iron could be used in the core or fewer turns of wire, whichever happened to be the cheaper. It is not advisable to use a transformer having poor iron, however, as distortion may be produced. The distortion: is produced by the way the iron behaves, when it is magnetised, and’ it may be serious. ‘There is also the question of magnetic saturation to. be considered, but the manufacturers usually advise -purchasers of their products how much current may safely be passed by the primary winding.