How to measure the impedance

Hello again,


Sometimes the output impedance will be specified simply to protect the amplifier or for other reasons. For example, if they spec 8 ohms then the output stage is designed to handle 8 ohms and not 4 ohms as that may harm the output stage, and not 16 ohms as that may mean higher distortion. When it comes to audio power amps i try to match the speaker to the recommended value for that amp.
Also, the internal design will always have a voltage limited power supply and using a speaker that is too high in impedance will not allow full output power for that amp.

audioguru said:

Some people still think that an amplifier's output impedance must be the same as the speaker's impedance in order to throw away 2/3rds of the power of the amplifier and so that the amplifier does not damp the resonances of a speaker.

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Can you buy 0.005ohm speakers?

Impedance matching was in the bad old valve days (as you know).

MrAl said:

Sometimes the output impedance will be specified simply to protect the amplifier or for other reasons. For example, if they spec 8 ohms then the output stage is designed to handle 8 ohms and not 4 ohms as that may harm the output stage, and not 16 ohms as that may mean higher distortion.

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No and no.
1) The load impedance is specified for an amplifier, not the extremely low output impedance (0.04 ohms or less) of the amplifier.
2) With a 16 ohm load, the distortion is less because the current and output power are lower.

#1 That's what i said.
#2 It depends on the actual amplifier design, doesnt it?

MrAl said:

#2 It depends on the actual amplifier design, doesnt it?

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No.
With less output current and less power output any solid state amplifier has less distortion.

audioguru said:

No.
With less output current and less power output any solid state amplifier has less distortion.

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I would agree, and so do the specs of any amp I've seen.