amplifier's "slam-factor"

That's a good question and one that i would like to know the answer to myself. While one can "tighten" and "stiffen" the bass by going gonzo on the power supply and filter cap reserve, it is not easy to make it "slam". Sean
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I cannot provide the answer to your question, however, I do not believe that the 'speed' or 'fast' actions of the transistors and/or high biasing automatically imply slam factor. Although these positive attributes would most certainly help to control and produce a well defined bass region even more than usual.

Even you stated that the Spectrals are known as a 'fast' amp yet lack that high slam-factor as you mentioned.

The Krell's and Levinsons are both known for a solid controlled bass, but I have never heard them known for their speed or being a 'fast' amplifier.

Fast has everything to do with reproducing the initial attack of a note and the ensuing decay of the same note which will also lead to more inter-transient silence between the notes giving the impression of perhaps a blacker background when in fact the listener is hearing more silence between the musical notes as the musician(s) intended.

Those amps lacking this speed will have difficulty reproducing the initial attack properly as well as the ensuing decay. And in the process subdue some of the micro- and macro-dynamics of the note. Even to the point where the notes appear to run together.

As one TAS reviewer asked in the course of a somewhat negative product review 'I wish somebody would explain why the tempo of one cdp appears slower than a competitor when in fact the tempo's of both cdp's are identical when compared to a metrinome'?

I may not be able to explain this very well, but to the best of my knowledge, this is exactly why.

-IMO

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...