Aball, the damping factor is calculated by dividing the resistance of the speaker by the output impedance of the amplifier: DF= Z(load)/Z(out). For an amp to have a damping factor of 100 into an 8 ohm load its output impedance would have to be .08. Since a speakers load/resistance changes with frequency (most anyway) the damping factor of an amplifier varies with frequency too. Above 100 is pretty good. When the numbers start getting really high they kind of get trival/splitting hairs. The difference between a damping factor of 175 and 1750 is a 0.5% change in control over the speaker. Some claim those really high damping factor start becoming marketing hype--particularly if other aspects of the design may have been neglected. Concern rises when an amp has an output impedance of say 2 ohms and into an 8 ohm load we now have a DF of 2, worst case (and it does happen with those SET's) things can actually go into the negative zone. (The equation is simplified: to account for the speaker cable, its resistance is added to the output impedance of the amp and then that sum is divided into the aformentioned equation.)
(Current drive amps are the only time one tries to match the output impedance of the amp directly to the speaker for a DF of 0: this in only done in active systems and rarely to my knowledge. Any other time the amplifier aspires to an ouput impedence of 0)
Slew rates matter: its an important spec. However, their worth has to be interpreted in the context of power and load resistance too. A less powerful amp doesn't need as high a slew rate as a bigger one. Into an 8 ohm load an 11V/us is acceptable for a 32 watt amp; for a 1,000 watt amp 64V/us is appropriate. It does depend on the bandwidth of the amp. And if slew rates get too high it can cause new problems.
This article briefly attempts to correlate some of the electrical/measurable aspects of amplifiers performance to subjective impressions.
http://sound.westhost.com/amp-sound.htm
(Current drive amps are the only time one tries to match the output impedance of the amp directly to the speaker for a DF of 0: this in only done in active systems and rarely to my knowledge. Any other time the amplifier aspires to an ouput impedence of 0)
Slew rates matter: its an important spec. However, their worth has to be interpreted in the context of power and load resistance too. A less powerful amp doesn't need as high a slew rate as a bigger one. Into an 8 ohm load an 11V/us is acceptable for a 32 watt amp; for a 1,000 watt amp 64V/us is appropriate. It does depend on the bandwidth of the amp. And if slew rates get too high it can cause new problems.
This article briefly attempts to correlate some of the electrical/measurable aspects of amplifiers performance to subjective impressions.
http://sound.westhost.com/amp-sound.htm