How can I tell if this is 3:1 transformer?

[rousejeremy]

I have a small audio transformer in my parts bin, and know idea what it is. Nothing written on it. I hope it's useful for an Octave pedal. Is there a way I can test to find out what ratio it is?

[maarten]

Put an AC voltage on the secondary side of the unknown transformer, measure this AC voltage (if you don't know this yet; e.g. you may use 6v3 from an amp for this). Then measure the primary side of the unknown transformer; divide this by the voltage you found on the secondary side. From memory I think that you would need a ratio of 1:1 up to 3:1 for an octave pedal. Most likely you will find a much higher ratio, if this audiotransformer was not meant for transistors but for a small tube amp, maybe something like 30:1. If that is the case, you might want to use it as an outputtransformer for a small amp.
You sometimes can recognize the secondary winding of the audio transformer by the gauge of the winding (thicker than the primary), if not so, you just have to try...
Maarten.

[sean k]

The voltage ratio squared equals the impedance ratio. So 10VAC in and 30VAC out means 3/1 turns ratio and 9/1 impedance ratio. so if you wanted 16ohms on the 1 side it's sqrt16 = 4 so 4/1 =4. So 4 x 4 x 9 =144ohms/16ohms.