Providers of audio amps normally publish the frequency response of their items that, sad to say, won’t always show you a great deal concerning the sound quality. I will clarify the meaning of this term and additionally offer some suggestions on how to interpret it whilst searching for an amp.
An amplifier is able to only work within a particular frequency range. Any signals outside of this range are going to be eliminated. As such the frequency response offers a significant clue regarding whether or not a specific amplifier could be suitable for a particular application. If the frequency range is 20 Hz to 20 kHz for example, the amplifier could amplify any signals with a frequency greater than 20 Hz and lower than 20 kHz. However, there is far more to comprehending the amplifier’s overall performance than merely taking a look at these figures.
In truth, an amplifier that has a frequency response from 10 Hz to 30 kHz can in fact have much lesser audio quality than an amplifier that provides a frequency response from 20 Hz to 15 kHz. Different makers appear to employ different ways in order to establish frequency response. Typically, the frequency response displays the normal operating range of the amp. Inside this range, the amp gain is basically constant. At the upper and lower cutoff frequencies the gain is going to decrease by no more than 3 decibels.
However, the frequency response commonly is utilized in order to misinform consumers by stretching the frequency range a good deal beyond the range in which the amp still operates correctly and also covers up the reality that the amp might not be linear. Therefore it is best to have a complete frequency response document. This kind of graph will reveal whether or not there are any sort of substantial peaks and valleys inside the operating frequency range. Peaks and valleys might cause colorization of the sound. If at all possible the gain of the amplifier should be linear throughout the entire working range.
You also need to look at the conditions under which the frequency response was calculated. You typically are not going to find any kind of information about the measurement conditions, however, in the producer’s data sheet. The fact is that lots of amplifiers will function in a different way with different loudspeaker loads. This is mainly because that different speaker loads can cause changes to the behavior of the output power stage of the amp.
The frequency response of Class-D amplifiers shows the greatest change with different speaker loads due to the built-in lowpass filter which removes switching noise from the amplifier’s signal. A varying speaker load is going to impact the filter response to some degree. Normally the lower the speaker impedance the lower the maximum frequency of the amplifier. Moreover, the linearity of the amplifier gain is going to be determined by the load.
Some amplifier topologies provide a mechanism to compensate for changes in the amplifier gain with different speaker loads. One example of these approaches utilizes feedback. The amplifier output signal after the interior lowpass is input to the amplifier input for comparison. If not designed properly, this approach could cause instability of the amp however. Different amps employ transformers and provide outputs for various loudspeaker loads. Apart from improving the frequency response of the amp, this technique generally also enhances the amplifier power efficiency.