The frequency response is by far the most commonly found parameter in order to define audio amps. Having said that, it may regularly be confusing and may not necessarily give a good indication of the audio quality. By way of example, the lower frequency may be 20 Hz and the higher frequency 20 kHz. However, there is certainly a lot more to understanding an amplifier's performance than simply knowing this simple range. Different makers often employ various methods in order to establish frequency response. At the lower and upper cutoff frequencies the gain will decrease by no more than 3 decibels.
Also, just examining these 2 numbers doesn't say a lot about the linearity of the frequency response. You additionally may need to look at the circumstances under which the frequency response was calculated. You usually will not find any information about the measurement conditions, unfortunately, in the producer's data sheet. This change is most obvious with many digital amplifiers, often known as Class-D small stereo amps as shown at the website www.amphony.com. Class-D amplifiers employ a lowpass filter within their output in order to reduce the switching components which are produced from the internal power FETs. A changing speaker load is going to affect the filter response to some extent. Some amp topologies provide a method to compensate for changes in the amplifier gain with different loudspeaker loads. One of these techniques uses feedback.