amplifier's "slam-factor"

It's a difficult question to answer...

First off, *if* you sit in a recording studio and dork with the control knob of an expander/compressor you'll probably be surprised to find that things have *more* impact when they are *compressed*! That means that when they have *less dynamic range* they sound louder and have more apparent impact.

The second thing is that an amplifier shouldn't have "slam factor" at all, per se. It should merely increase the level of the source signal faithfully - that's the theory.

The difference between two amps that have the same power ratings is often in the implementation. As the complexity and level of the signal increases the demands upon the amplifier goes up. This is where many amplifiers start to fall apart (subjectively).

It's too complex to discuss the inner workings of a given amplifier's circuit, but even for identical circuits, the power supply *does* have a huge effect. As the amp draws more and more power -even instantaneously - the power supply has to respond with enough current to keep the voltage up. Almost NONE do this adequately.

The smaller and lighter the amplifier (except switching supply amps - and then the wall is a major factor) the less likley it can perform equally well at full power as it does at 1 watt. My Symphony No. 1 amplifier uses a huge power supply at >2kva in the iron and 500,000 ufd for filter caps with 140 amp Hexfred rectifiers on 1/4" copper buss bars to keep just this problem to an absolute minimum!

This drives a pair of 180watt per channel modules. At full power, both channels driven simultaneously to heavy clipping the rail voltage ducks less than ONE volt. Most amps drop more like 5 - 10 volts on peaks. Some drop more.

Subjectively, you can think of this as the difference between a drive shaft on a car that is really really stiff and one that is springy. Or maybe a transmission that slips vs. a direct connection.

It's likely that "slam factor" in amps is not really there, while the compression factor comes in to play with tube amps, and the power supply is a major issue with all amps. You can hear this stuff.

Imho, as any type of amp design is implemented better and better, they all start to sound surprisingly similar - meaning the best implementations of the best designs tend to sound very much alike be they SS, Mosfets or tubes...(properly applied, of course).

Now, there is "jump factor" in speakers...

With live, non-amplified music does anyone ever hear slamming bass? I've heard deep, forceful tones that carry a physical impact, but I've never been exposed to that sharp, highly edge defined bass sound except for when I'm listening to high end audio systems. I'm not entirely convinced, but the stereotype Krell/Bryston bass sound could be a form of coloration. Which is not to say that on rock and other strongly rhythmic music that it can't be a very pleasant colorations.

I just replaced my 300wpc Krell FPB-300 with a 150wpc Spectral DMA-150 Mk2 (speakers are Aerial 10T). At first blush it had seemed that I had taken a step backwards in terms of slam. But after further critical listening I realized that the sound had taken a step forward in terms of slam. A great example of how the slam changed could be found by listening to Reiner's Pictures (Classic reissue LP).

The sound of the bass drum on this using the Krell tended to fill the room with a dynamic, fat, "thunk" -- something you could really feel in your belly.

With the Spectral amp the overall sense of slam seemed to take a step backwards because it wasn't as large and as fat. The sound though more closely represented a bass drum being hit with a mallet. The sound of the mallet hitting the hit was sharp and seemingly more dynamic sounding than it had been with the Krell. There also was less of a sense of overhang; the notes seemed to disappear more quickly with the Spectral.

Having played the bass drum before, it seemed to me that the Spectral amp was likely portraying the sound more realistically -- and that the slower Krell was allowing the bass drum sound to hang around a bit longer than it should have been.

I think my observations seem to support the very nicely articulated comments by Stehno above.

What about the slew rate of an amplifier?

Does this play a part in the perception of "slam" factor?

Just throwing out thoughts,
benny

i suggest you look at the control that each amp has on the drivers "damping factor"

Aleph 5 50
SF Power2 100
ML 33H 830
Krell ??? ???

Like Atzen811 slewrate factor I suggest that the ability of the amp to control the drives is very important and likely to affect the sense of slam

aleph very tube like
sf very tube to kinda ss
ml very ss with an incredible sense of control and quiet
krell ?????????

not solving anything here but interested to hear comments and ideas