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vendredi 14 mars 2014

Suggestions For Making An Informed Decision Whilst Looking For Audio Amps

By Marta McBrian


The frequency response is one of the most often found parameter to define stereo amplifiers. However, it can regularly be deceptive and might possibly not offer a good indication of the sound quality. You will possibly not understand fully the way in which the frequency response is determined. I am going to discuss what precisely this term means. Ideally you will be able to make a much more educated purchasing decision. An amplifier will magnify a sound signal that is inside the frequency response range. Generally a lower and upper frequency are provided, just like 20 Hz - 20 kHz. This particular spec shows that the amp has the capacity to amplify audio within that frequency range. Then again, there is certainly far more to understanding the amplifier's functionality than simply taking a look at these numbers.

A large frequency response does not necessarily mean the amp has excellent audio quality. For instance an amp having a frequency response between 30 Hz and 15 kHz might sound better than a different amplifier with a response between 10 Hz and 30 kHz. In addition, each maker, it appears, implements a different technique of specifying the minimum and maximum frequency of their amps. The most popular technique is to describe the frequency response as the frequency range within which the amplifier has rather constant amplification with a maximum drop of 3 decibel (dB). Generally the drop in amplification is greatest at the upper and lower frequency.

However, many companies overlook this particular convention. They push the lower frequency and upper frequency to where the amp rarely offers any gain. In addition, these numbers say almost nothing about precisely how linear the amp is operating inside this range. A complete frequency response chart, on the other hand, will show if there are any peaks and valleys and in addition show how the frequency response is to be interpreted. Peaks as well as valleys could cause colorization of the audio. Ideally the gain of the amp should be linear throughout the entire working range. To better comprehend the frequency response behavior of a specific model, you should try to find out under which circumstances the response was calculated. You will probably find this information in the data sheet of the amp. Then again, most manufacturers will not show those in which case you should make contact with the manufacturer directly. The fact is amplifiers may have different frequency responses depending on the speaker which is attached.

The circumstances under which the frequency response was determined may also be necessary to fully understand. One condition which may impact the frequency response is the impedance of the speaker attached to the amp. Typical speaker impedances range from 2 to 16 Ohms. The lower the speaker impedance the higher the strain for the amp. Mostly current digital or "Class-D" amps can have changes in the frequency response with different loads. The main reason is the fact that Class-D amplifiers make use of switching FETs as the power stage which produce significant amounts of switching components. These components are eliminated using a filter that is part of the amplifier. Then again, the frequency response of the amp now will depend on the loudspeaker load because the behavior of this lowpass filter is influenced by the load impedance. Usually the lower the speaker load impedance the lower the upper cut-off frequency of the amp

This change is most noticeable with most digital amplifiers, also referred to as Class-D amps. Class-D amplifiers use a lowpass filter in their output as a way to reduce the switching components that are produced through the internal power FETs. The lowpass filter characteristic, on the other hand, greatly depends upon the attached load. A number of the newest digital amps feed back the music signal after the lowpass filter to be able to compensate for this tradeoff and to make the frequency response of the amp independent of the connected load. Then again, if the amplifier is not constructed properly, this sort of feedback could potentially cause instability and also lead to loud noise being generated by the amplifier if particular speakers are connected. Other amplifiers make use of transformers and offer outputs for different loudspeaker loads. Apart from improving upon the frequency response of the amp, this technique normally furthermore enhances the amplifier efficiency.




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