Pure class A amplifiers = "slow" amplifiers?

The bug-a-boo about A/B amps is crossover distortion where, as the waveform crosses zero and changes polarity, one output transistor turns off and the other turns on. The very first transistor power amps caused distortion of the waveform as this happened. It was largely responsible for their poor sound quality. Once this effect was recognized designers have taken pains to minimize crossover distortion. Not all A/B amps are created equal. Good ones exhibit little or no crossover distortion, although they may have other problems, most of which could affect class A amps also. However, crossover distortion is easy to understand, and is often cited in criticisms of A/B amps.

Class A amps are not slower or faster than class A/B and do not inherantly have more distortion. Class A actually potentially has less distortion because the active device is biased in a manner so that it conducts the through the entire cycle of the input signal. Of course can drive the active device too far in one direction or the other and end up with a distorted waveform - distorted sound. A Class A device avoids the distortion caused when you process something less than the entire cycle with one active device and the remainder with a second active device, because the point where the conduction crosses over causes a glitch. However, this is not really a problem if the system is properly designed. Why would anyone want to use less than Class A topology ? Because you save on the size of the active devices, if you are only conducting current half the time you create less heat and can use a lower wattage component. A well designed CLass A should sound no better or no worse and no different than a well designed Class A/B. Now there are a host of reasons that one amplifier may sound different than another but whether the design is CLass A or Class A/B is too limited of a criterion to say how an amp will sound or how well it will be able to drive a load.

Guidocorona, my impression of real Krell amps (pure class A power only amps, no HT or integrateds) is that they are warm, deep, and excell at both micro and macro dynamics. I'm a big fan.

In my opinion dynamic range is more loudspeaker related than amplifier. For if you rely on massive power to get dynamics you are forcing your loudspeakers to perform, requiring massive cone excursions and much heat to crossover parts and voice coils all detrimental to sound quality and loudspeaker life span. I find loudspeakers that are efficent and need little power to provide far far better dynamic range and speed than conventional loudspeakers that need huge power just to sqeak out limited SPL. Since the driver cones are hardly moving in hi-eff designs they reveal hidden details that are lost to massive excurtion designs. Plus hi-eff are at ease at almost all SPL levels since these designs are never forced or pushed they dont heat up as much or sound fatiging like convetional designs do at HI-SPL. Once you hear proper replicated dynamic range conventional loudspeakers with massive power sound slow and compressed. CLass A is not the cause at all its the loudspeakers.

Johnk...Although Maggies aren't high efficiency speakers, they do have very small diaphragm excursion, and I believe this may be a lot of the reason they sound good. When I designed a cone driver subwoofer system to go with my Maggies a prime criteria was minimal cone excursion. What happens to the typical subwoofer cone is obscene!! I ended up with three subwoofer systems, for my three front channels, each including a 15" driver and a 12" driver. I get very strong bass with quite modest cone excursion.