A note on terminology: Unless there are some extremely unusual exceptions out there, all audio power amplifiers amplify both voltage and current, so the terminology in the subject line of the thread is a bit misleading.
Solid state amplifiers having near zero output impedance are sometimes referred to as being voltage sources, meaning that for a given input voltage their output voltage will remain constant regardless of load impedance (within the limits of their capability). Referring to them as being voltage sources is accurate terminology, to a very close approximation. (The reason it is a very close approximation, rather than being exact, is that no real world amplifier can have an output impedance that is exactly zero).
Tube amplifiers, having significant output impedances, are sometimes referred to as being current sources, which strictly speaking would mean that for a given input voltage the current they output would remain constant regardless of load impedance (within the limits of their capability). That is NOT accurate terminology, except in the extremely loose sense that their output current will vary LESS as a function of load impedance than in the case of an amplifier having near zero output impedance.
It may be helpful to read this Wikipedia writeup on the voltage divider effect. In the first figure, consider Z1 as representing the output impedance of the amplifier, and Z2 as representing the impedance of the speaker, which will be different at different frequencies.
Regards,
-- Al
Solid state amplifiers having near zero output impedance are sometimes referred to as being voltage sources, meaning that for a given input voltage their output voltage will remain constant regardless of load impedance (within the limits of their capability). Referring to them as being voltage sources is accurate terminology, to a very close approximation. (The reason it is a very close approximation, rather than being exact, is that no real world amplifier can have an output impedance that is exactly zero).
Tube amplifiers, having significant output impedances, are sometimes referred to as being current sources, which strictly speaking would mean that for a given input voltage the current they output would remain constant regardless of load impedance (within the limits of their capability). That is NOT accurate terminology, except in the extremely loose sense that their output current will vary LESS as a function of load impedance than in the case of an amplifier having near zero output impedance.
It may be helpful to read this Wikipedia writeup on the voltage divider effect. In the first figure, consider Z1 as representing the output impedance of the amplifier, and Z2 as representing the impedance of the speaker, which will be different at different frequencies.
Regards,
-- Al