Anything as " fast" as SPECTRAL gear?

@Mapman ... I seem to recall Ralph (Atmasphere) posted comments some years back about the impact and import of high damping factors (DF) on woofer control. DF, of course is simply speaker impedance at a particular frequency (usually in the bass range), divided by the amp's output impedance at the same frequency.

As I also recall, Ralph may have said that a DF over 20 doesn't make that much of a difference in woofer control. In fact ... the dark side of a high DF is that it is oftentimes achieved by using high negative feedback (NF) which is used to achieve in part low output impedance, which augments high DF. Ralph has written much about the sonic downsides of using NF.

If Ralph picks up this post, I'm sure he'll fill in the gaps.

Bruce

P.S. -- FWIW, the slew rate of my ARC Ref 150 is 13 volts/microsecond. The vaunted ARC GS-150 is the same. The mighty ARC Ref 750 is 20 volts/microsecond.

My point ... I have no idea what it all means.

But top rated and reviewed ARC amps like the Ref 150, the GS 150 and the mighty Ref 750 have slew rates nowhere near Ralph's amps which he says are 600 volts/microsecond.

Maybe Ralph can put this spec into perspective for us.

So Al, what does that mean in the context of ARC ref amps. As I mentioned above, the slew rate for my amp (150 wpc) is a paltry 13 volts/microsecond and the rise time is a sluggish 2 microseconds. The top of the line Ref 750 has a slew rate of 20 volts/microsecond and a rise time of 1.5 microseconds.

Based on your comments, I gather a CD will be over before the amp is able to get a signal to the speakers. Almost like playing a 45 rpm record at 33 rpm on a turntable. :)

Of course, I'm being tongue in cheek, but I gather there is some overkill in the specs. Kinda like an amp with a DF of 1000 ... way overkill. Ralph has mentioned that a DF over 20 is a waste.

Please clarify.

Bruce

Bombaywalla, I generally get your points about slew rate specs and the impact on bandwidth, especially if there are large power demands placed on the amp at higher frequencies.

FWIW, I seem to recall many years ago that I spoke with Leonard, ARC's former customer service rep, about the slew rate issue. Len explained that the design of an amp takes into account many factors and compromises, slew rate being just one of many. The same hold true for negative feedback, DF and so forth.

So, in the end, Len wisely said that it comes down to how does the amp in question sound in real life operating conditions taking into account all of these design considerations and trade-offs. That's what engineers do all the time.

As to your specific point that a 10K square wave pic might not look so pretty at high power outputs ... well that might be true. But as we all know, most of an amp's power demands are in the bass and midrange frequency spectrum.

I surmise that listening to an amp pumping even 50 watts of power into moderately sensitive speakers at 10K Hz would likely melt your ears ... assuming the tweeters could take the load.

Al ... what are your thoughts??