14-06-2022, 07:36 PM
In the 1920s they used 2K or 4K loads, either headphones, or earphone driver on a horn or a moving iron with a 10" to 14" free standing paper cone (no spider at base or surround at outer edge. The GB battery had 1.5V taps to allow for HT wear or different triodes. The tap being adjusted to centralise the moving iron it there was no meter.
From about 1933 the speakers were about 2 Ohm to 20 Ohm and often with a winding in series with HT ( 100 Ohms) or across HT (1000+ Ohms) instead of a magnet for greater efficiency because powerful enough magnets very large and expensive. Battery sets had big magnets on the speakers. The moving Iron 2K to 4K speakers ended between 1930 and 1934.
A 9V or 6V mains transformer of sufficient size won't saturate, these sets had low anode bias current more like a DL92 or DL96 than and EL84. I've used clock-radio mains transformers on battery valve sets (the basic LED clocks or clock radios cheap enough to buy new for parts!) and they sounded fine. I've used bigger 10W to 15W 6V to 12V transformers on 6V6 and similar with success.
From about 1933 the speakers were about 2 Ohm to 20 Ohm and often with a winding in series with HT ( 100 Ohms) or across HT (1000+ Ohms) instead of a magnet for greater efficiency because powerful enough magnets very large and expensive. Battery sets had big magnets on the speakers. The moving Iron 2K to 4K speakers ended between 1930 and 1934.
A 9V or 6V mains transformer of sufficient size won't saturate, these sets had low anode bias current more like a DL92 or DL96 than and EL84. I've used clock-radio mains transformers on battery valve sets (the basic LED clocks or clock radios cheap enough to buy new for parts!) and they sounded fine. I've used bigger 10W to 15W 6V to 12V transformers on 6V6 and similar with success.
