How to measure the impedance

[MrAl]

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.

 

[Nigel Goodwin]

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.

Can you buy 0.005ohm speakers?

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

 

[audioguru]

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.

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.

 

[MrAl]

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

 

[audioguru]

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

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

 

[Nigel Goodwin]

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

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