Guidelines For Buying Stereo Amplifiers

The frequency response could be the most commonly located parameter to characterize audio amplifiers. Nonetheless, it could often be misleading and may possibly not necessarily give a good indication in the sound good quality. I will clarify the meaning of this term and also give some suggestions on how to interpret it although seeking an amplifier.



An amplifier is designed to magnify an audio signal adequate to drive a set of speakers to medium or high volume. Manufacturers usually publish the frequency range over which the amp operates. Typically a lower and upper frequency are given, for example 20 Hz - 20 kHz. This specification indicates that the amplifier is able to amplify music within that frequency range. You could be tempted to choose an amp that offers the largest frequency response. Nonetheless, there is more to understanding an amplifier's performance than just realizing this easy range.



In fact, an amp that has a response from 10 Hz to 30 kHz can truly have much poorer sound high quality that an amp that gives a frequency response from 20 Hz to 15 kHz. Distinct manufacturers appear to make use of various strategies to define frequency response. Probably the most commonly used way would be to describe the frequency response as the frequency range within which the amplifier will have fairly constant amplification having a maximum drop of 3 decibel (dB). Usually the drop in amplification is highest at the lower and upper frequency.

Even so, some producers push this common to the limit and will list an upper frequency where the amplifier will barely generate a signal anymore. Also, just seeking at these 2 numbers does not say considerably regarding the linearity from the frequency response. Thus it is best to have a complete frequency response chart.



Such a chart will show whether you will find any significant peaks or valleys within the operating frequency range. Peaks and valleys can trigger colorization of the audio. Ideally the amplifier must have a continuous acquire inside the entire frequency response with the exception with the drop off in the lower and upper limit. Apart from the frequency response, a phase response diagram will also tell a great deal about the efficiency and sound top quality in the amp.



You also have to look in the circumstances under which the frequency response was measured. You generally won't uncover any information concerning the measurement circumstances, even so, in the manufacturer's information sheet. The fact is that a lot of amplifiers will behave differently with various speaker loads. This really is due to the reality that distinct speaker loads will trigger alterations towards the behavior of the output power stage of the amp.



This change is most noticeable with several digital amps, also known as Class-D amps. Class-D amps have a lowpass filter in their output so as to suppress the switching components which are generated by the internal power FETs. Nonetheless, the frequency response of the amp now depends upon the speaker load since the behavior of this lowpass filter is affected by the load impedance. Usually the lower the speaker load impedance the lower the upper cut-off frequency with the amplifier.



Some of the most recent digital amplifiers feed back the audio signal right after the lowpass filter so as to compensate for this tradeoff and to make the frequency response from the amp independent with the attached load. Nevertheless, if the amp just isn't developed correctly, this kind of feedback can cause instability and lead to loud noise becoming generated by the amp if specific speakers are connected. Other amps use transformers and supply outputs for various speaker loads. Apart from enhancing the amplifier response with the amp, this technique typically also improves the amplifier efficiency.