Phones To An A.C. Set

Radio Record, Volume V, Issue 11, 25 September 1931, Page 8

Phones To An A.C. Set

Wit regard to the three methods of fixing headphones to an electrie set, as shown in the "Radio Re cord" recently, "Loco" writes :- "My set is a six-valve A.C. 1 de sired to relay head-phones to another part of the house. I tried a little ex perimenting. I tried the third method described, and could get only a ‘loud humming whistle on speaker and phones. I then put two .001 mfd. con densers in series with the 1 mfd. condensers and found I could hear fairly well, but only over a large amount of them. "Not knowing anything about the sel -i.e., as to whether it is ‘push-pull,’ ‘pull-push,’ ‘push-in,’ ‘push-out,’ etc.. I tried the first method as well, but this time I got a loud continuous clicking sound in phones and speaker. "Now I come to my ‘discovery. Without detailing how I found it, I will proceed to describe it to you. "A eable containing three insulated wires, red, black and yellow, goes from my set to the transformer and speaker. "J took a wire from where the yellow covered wire joins at back of transformer and took it to a 1 mfd. condenser, connected one wire of phone to other terminal of condenser and connected other wire from phone to earth (using a different earth connection from that used by set), and found that phones worked splendidly, practically free from objectionable hum; _ only when speaker was turned up to usual volume the volume was too much on phones on the ears, but I connected a .001 mfd. condenser (C©2) in series with the 1 mfd. condenser and found that the volume was better controlled, and the static ‘splashes’ when listening to a distant station were not so much like a blow on the eardrum with a hammer. "T have fitted an A.C. snap switch in series with one of the wires from transformer to voice coil, and I can now shut off sperker and sit in another room and listen -to clear and *hum-free’ concerts on the phones."