fast 'rise time' or a fast waveform response vs a slow one.
Look at the square waves in test teports.
A 'fast' amp has a near vertical rise in the squarewave. A 'slow' amp has a curved line in the vertical response to a square wave.
Some amps start out the squarewave with a steep, near vertical line and 'tire out' and start to curve off on the rise.
Some cannot maintain the power and curve off the square top of the waveform towards the far edge.
The graphic chart is not all there is to a power amp, but the response to a squarewave tells a lot about how robust the circuitry really is. Advertising claims aside.
What the 'fast' means in sound is powerful transients. Crisp attack.
Slow means warm. Sound is rounded out. mellow.
Look at the square waves in test teports.
A 'fast' amp has a near vertical rise in the squarewave. A 'slow' amp has a curved line in the vertical response to a square wave.
Some amps start out the squarewave with a steep, near vertical line and 'tire out' and start to curve off on the rise.
Some cannot maintain the power and curve off the square top of the waveform towards the far edge.
The graphic chart is not all there is to a power amp, but the response to a squarewave tells a lot about how robust the circuitry really is. Advertising claims aside.
What the 'fast' means in sound is powerful transients. Crisp attack.
Slow means warm. Sound is rounded out. mellow.