b4icu,
Guess I’ll school you some more if that’s what you want.
If you’re using speakers with benign phase angles and unabusive impedance fluctuations, you hardly need a damping factor at all. Having some insanely high damping factor doesn’t add anything! A factor of 15 or 20 is plenty sufficient and there’s plenty of amps that prove that, chief among them the First Watt J2 and many SET amps.
All gain devices become more nonlinear as they swing larger voltage. There’s a good argument to be made for speakers designed to be benign and efficient, but a more reactive speaker has advantages as well, such as utilizing current draw and phase angles to bully the drivers into behaving. Even with the most reactive speakers a damping factor more than 200 is pretty much pointless. How much do you want the amp to misbehave in response to the speaker? That’s why McIntosh likes their output transformers on their SS amps. They give a DF around 50 or so and keep the gain devices behaving like proper voltage sources.
With pairs of MOSFETs, JFETs, or BJTs as output devices you’re going to get a DF around 50. Double the number and you get about double the damping factor. At some point you’re not well optimized by using more gain devices and for the vast majority of amps that’s around 2 or 3 pairs for mid power amps. So if you want more damping factor you’re adding negative feedback. You can add 95% of the open loop gain and get a VERY high damping factor. 1500 or so is totally possible with enough feedback. It’s very easy to do. Nobody does it because it sounds like hell. We learned a long time ago damping factor isn’t the end all. The techniques to get a very high damping factor always contribute to more complex distortion. Since damping factor primarily effects bass, the trade off tends to be more controlled bass at the expense of brighter, more grating treble because of the more complex distortion.
You speak as though impedance is the only act in town. You don’t seem to grasp that a damping factor describes the inductance and capacitance of the circuit. When an amplifier damps an uncontrolled woofer, it’s acting as a giant inductor. All these electrical characteristics play an equal role, and you don’t seem to grab that. Nobody should take you seriously.
Guess I’ll school you some more if that’s what you want.
If you’re using speakers with benign phase angles and unabusive impedance fluctuations, you hardly need a damping factor at all. Having some insanely high damping factor doesn’t add anything! A factor of 15 or 20 is plenty sufficient and there’s plenty of amps that prove that, chief among them the First Watt J2 and many SET amps.
All gain devices become more nonlinear as they swing larger voltage. There’s a good argument to be made for speakers designed to be benign and efficient, but a more reactive speaker has advantages as well, such as utilizing current draw and phase angles to bully the drivers into behaving. Even with the most reactive speakers a damping factor more than 200 is pretty much pointless. How much do you want the amp to misbehave in response to the speaker? That’s why McIntosh likes their output transformers on their SS amps. They give a DF around 50 or so and keep the gain devices behaving like proper voltage sources.
With pairs of MOSFETs, JFETs, or BJTs as output devices you’re going to get a DF around 50. Double the number and you get about double the damping factor. At some point you’re not well optimized by using more gain devices and for the vast majority of amps that’s around 2 or 3 pairs for mid power amps. So if you want more damping factor you’re adding negative feedback. You can add 95% of the open loop gain and get a VERY high damping factor. 1500 or so is totally possible with enough feedback. It’s very easy to do. Nobody does it because it sounds like hell. We learned a long time ago damping factor isn’t the end all. The techniques to get a very high damping factor always contribute to more complex distortion. Since damping factor primarily effects bass, the trade off tends to be more controlled bass at the expense of brighter, more grating treble because of the more complex distortion.
You speak as though impedance is the only act in town. You don’t seem to grasp that a damping factor describes the inductance and capacitance of the circuit. When an amplifier damps an uncontrolled woofer, it’s acting as a giant inductor. All these electrical characteristics play an equal role, and you don’t seem to grab that. Nobody should take you seriously.