[tab10672]

I recently bought a homebrew 2 tube battery radio with all parts intact with 01a type sockets but the audio transformer is labeled 10 to 1 ratio, most others I have seen are closer to 3 to 1, will this trans work ok with 2 01a's? Thanks Todd

[morzh]

In tube radios I have never seen a ratio as low as 3:1. Which would mean that even an 8 Ohm speaker would present as 72 Ohm impedance to the tube which is waaaaay low.

Your typical ratio at least 20-30.
Of course if your power voltage is very low and output currents high then it is possible but then we are talking transistor level voltages.

[Alan Douglas]

What we have here is a failure to communicate...

The 1920s interstage transformers were marked "3 to 1" but what they meant was "1 to 3."

The 10:1 will work but these tend to have a peaky audio response, not much treble, and the primary inductance is low so they don't have any bass response either.

[tab10672]

Thanks for the info, I think I will try it out because 1-its original, 2-it tests good, and 3-it has the early 20's look compared to the generic 3 dial "trans/choke" look. Thanks again Todd

[BrendaAnnD]

Morzh, in the radios he's talking about, they didn't use 8 ohm speakers. Normal speaker impedence was around 1K-3K, think feeding a speaker directly off the plate of the output tube (basically those old horn speakers were just an earphone driver feeding into the horn). The sound was pretty atrocious by even 1930's standards, but the novelty of having a "loudspeaker" on a radio was still a selling point.

[tab10672]

The schematic included with this radio actually calls for phones rather than a horn but I think it should at least drive one even if at low volume. Todd