@Lewinskih01, thank you kindly for the nice words. And for the generally excellent and informative post. But a little of it isn’t quite correct.
SETs are not constant current sources, which of course would mean that they provide an amount of current that remains essentially constant as load impedance varies, as long as they are operated within the limits of their maximum voltage, current, power, and thermal capabilities. They, and also push-pull tube amps, are not constant power sources, either. What is fair to say is that to a very loose approximation most of them behave as constant power sources, and how loose that approximation is depends on their output impedance. While a few others that have unusually high output impedances loosely approximate behaving as constant current sources, to a degree that depends on their output impedance.
As we have said, nearly all solid state amps maintain voltage that remains essentially constant into varying load impedances (for a given input voltage to the amp), as long as they are operated within the limits of their maximum voltage, current, power, and thermal capabilities. (Certain First Watt amps that have been intentionally designed to have high output impedances are notable exceptions). While SET and push-pull tube amps, when operated within their capabilities, will deliver more voltage and less current as load impedance increases, while delivering less voltage and more current as load impedance decreases. But the product of voltage and current in those cases will not remain constant for most such increases or decreases.
To see that, consider a tube amp to be an ideal voltage source (having an output impedance of zero, and outputting a voltage V) in series with a resistor, denoted as R1, that is equal to the amp’s output impedance. And consider the speaker impedance to be R2.
Per the voltage divider effect the voltage appearing across the speaker will be (V x R2)/(R1 + R2). The current provided to the speaker will be V/(R1 + R2). Plugging various values for R1 and R2 into those formulas, and calculating the product of the voltage and current provided to the speaker, will illustrate my point.
For example, consider an amp having an output impedance of 2 ohms (which is actually a good deal higher than the output impedance of the 4 ohm tap of the Line Magnetic SET amp that was referred to earlier), and speaker impedance that increases from 4 ohms at one frequency to 8 ohms at another frequency. You will find that both the current and the power that are delivered into 8 ohms are significantly less than what is delivered into 4 ohms, assuming the amp is operated within the limits of its maximum capabilities into both impedances.
Best regards,
-- Al
SETs are not constant current sources, which of course would mean that they provide an amount of current that remains essentially constant as load impedance varies, as long as they are operated within the limits of their maximum voltage, current, power, and thermal capabilities. They, and also push-pull tube amps, are not constant power sources, either. What is fair to say is that to a very loose approximation most of them behave as constant power sources, and how loose that approximation is depends on their output impedance. While a few others that have unusually high output impedances loosely approximate behaving as constant current sources, to a degree that depends on their output impedance.
As we have said, nearly all solid state amps maintain voltage that remains essentially constant into varying load impedances (for a given input voltage to the amp), as long as they are operated within the limits of their maximum voltage, current, power, and thermal capabilities. (Certain First Watt amps that have been intentionally designed to have high output impedances are notable exceptions). While SET and push-pull tube amps, when operated within their capabilities, will deliver more voltage and less current as load impedance increases, while delivering less voltage and more current as load impedance decreases. But the product of voltage and current in those cases will not remain constant for most such increases or decreases.
To see that, consider a tube amp to be an ideal voltage source (having an output impedance of zero, and outputting a voltage V) in series with a resistor, denoted as R1, that is equal to the amp’s output impedance. And consider the speaker impedance to be R2.
Per the voltage divider effect the voltage appearing across the speaker will be (V x R2)/(R1 + R2). The current provided to the speaker will be V/(R1 + R2). Plugging various values for R1 and R2 into those formulas, and calculating the product of the voltage and current provided to the speaker, will illustrate my point.
For example, consider an amp having an output impedance of 2 ohms (which is actually a good deal higher than the output impedance of the 4 ohm tap of the Line Magnetic SET amp that was referred to earlier), and speaker impedance that increases from 4 ohms at one frequency to 8 ohms at another frequency. You will find that both the current and the power that are delivered into 8 ohms are significantly less than what is delivered into 4 ohms, assuming the amp is operated within the limits of its maximum capabilities into both impedances.
Best regards,
-- Al