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RE: I can point to an output transformer but what do they do???

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In Reply to: RE: I can point to an output transformer but what do they do??? posted by djn on March 30, 2008 at 05:41:56

Speakers have an impedance of 4 to 16 ohms.

A 2A3, for example, has an output impedance of around 800 ohms. You want less than the impedance of the speakers.

A transformer-coupled 2A3 produces lots of voltage, but little current. You want current.

You need around 100 volts (+50V to -50V) to drive the 2A3 at full output. The 2A3, in turn, has a gain of roughly 3.5 (I don't remember the exact figure). So you have 300-350 volts. You only need around a tenth of that.

Using a transformer 2:1 you reduce voltage by two and impedance by four. The 800 ohms are now 200 ohms. Current, in turn, goes up by the same ratio voltage is reduced.

This is the only thing an output transformer does. Some are just better than others.

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