How to determine Audio Transformer Ratio of 1:10 at Digikey


I'm just starting to work with Transformers and while doing electronic experiments I found that I didn't know much. I'm trying to find an Audio Transformer with a ratio of 1:10 or 1:20 with an inductance of about 670 Ohms. After searching through the DigiKey website on Audio Transformers everything appears to have a ratio of 1:1. But there are specifications like 3.4kCT Primary, 4/8/16 Secondary.

What does the CT mean? And How do I calculate based on these numbers what the ratio would be or to find this type of transformer I suppose it's not a Audio Transformer any longer.

Can I find this transformer at Digikey?

Best Answer

Audio transformers are normally specified in terms of impedances. Your 3.4kCT to 4/8/16 transformer is intended to have a primary impedance of 3.4 kΩ (center-tapped) when the secondary taps are connected to 4, 8 or 16 Ω, as appropriate.

The transformer itself does not actually have a particular impedance, but it does transform impedances. You can infer from these specifications that it has impedance transformation ratios of 3400/4 = 850, 3400/8 = 425 and 3400/16 = 212.5, respectively.

The impedance transformation ratio is the square of the turns ratio, so you can further infer that the turns ratios are approximately 29:1, 29:1.4 and 29:2, again, respectively, and these turns ratios are the voltage ratios you can expect to see.


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