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Old 18th Jul 2019, 11:59 pm   #10
Radio Wrangler
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Default Re: "Matching" transformer.

On top of all this there are transformers designed to pass chosen amounts of max power to speakers in 100v line systems. Systems can have many speakers and with different amounts of power assigned to different speakers. Just tot up the total power the speakers are set for and you need a 100v line amp that is comfortable at that power.

There is no real 'matching' in the max power transfer theorem, or in the zero reflection senses. The impedance of a given driver's voice coil is simply transformed into te right impedance needed to take the chosen (tap-selected) power from the defined voltage common line.

Seen as an RF assemblage it would be a right mess with reflections bouncing between all points. But at audio frequencies and the cable lengths involved, it works fine.

100v line is too low a Z for comfort with valves, so output transformers are used in most amps.

100v line is too high a Z for comfort with power transistor voltage ratings, so transistor amps had to be transformer-based which was common in the early days. Transformerless amps are doable, now, but are still less convenient.

David
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