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Old 16th Jul 2019, 7:07 am   #7
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 5,776
Default Re: "Matching" transformer.

David's explanation is why I was very careful in my choice of words, " an amplifier designed for 3Ω" rather than "an amplifier having 3Ω output impedance."

Basically, the matching transformer enables you to use an amplifier designed for one particular load, to a speaker you happen to have which is unfortunately of a different impedance.

Synchrodyne's comments about the transformer having a very low DC resistance are worth bearing in mind, but that should only be a problem if you push very low frequencies through the amplifier, or the amplifier puts a large surge current through the load such as, on switch-on. A real speaker will limit this, a transformer might briefly saturate and allow an unusually big current to flow through the output transistors. Of course, such an amplifier is not what you'd want to use with expensive speakers in the first place!
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