ABOUT HEADPHONES

Radio Record, Volume I, Issue 9, 16 September 1927, Page 15

ABOUT HEADPHONES

+ HINTS ON THEIR USE The best way to tell if a pair of ‘phones is in good condition is to put the ’phones on and place the end ot one of the leads between the teeth. Rub a key or nail npon the other lead, and the weak galvanic currents set up in the body will cause a scraping sound in the earpieces, which will correspond with the rubbing of the key. Such a current 1s very weak, and is a hetter test of continuity than the usual drycell test, The headphones can be put to a great variety of uses in connection with the testing of various parts of the set, and really comprise a most efficient and delicate testing instrument. For example, if 1t is doubtful whether aunother pair of ’phones or a coil have a break in the windings, it is only necessary to connect them up in series with a battery or dry cell, and with a pair of known good *phones, when the making and breaking of the circnit (if continuous) will give rise to clicks in the headphones, Many people think that *phones will look after themselves without any attention, and this is a great mistake. If they are dropped, the jar will almost certainly knock some of the magnetism out of the magnets, which of course impairs their efficiency. Therefore, when you have finished listening-in, do not throw the ’phones on the table, but hang them on a rail on a dry wall. When trying to get a station that is onlv just out of hearing, instead of frantically twisting condenser knobs, or adjusting your crystal or filament current, why not try loosenmy or tightening the caps of your phones? The tension on the diaphragm has a lot to do with signal strength. For crystal sets the ’phones may be connected without consideration of polarity, but when connecting to afy valve circuit, and this includes anrplifiers also, the coloured cord shonld be connected to the ’phone connection on the set that joins the positive of the high tension. If there is a cord marked with red, that will be the positive, or if only one cord is marked with anv colour, that will probably be the positive. } If *phones are continually connected the wrong way round on valve sets, the permanent magnets will be gradually weakened, and Joss of volume will result, making distant reception more difficult.