1. Power Many people ask others about the performance of the amplifier. The opening asks how much power it is. It seems that the bigger the power, the better. In fact, in the family, the power is not too big. Some of the power amplifiers are available in the market, some of which are marked with 300W to 400W per channel, but there is only one 200W transformer in the machine. The power tube is paired with two MJ2955 and two N3055, or it is composed of TDA2030A. The power amplifier composed of such a power tube will appear to be incapable of expressing great dynamics, and the musical charm is not good enough. If divided by power, the peak power of music does not reach the requirement of 300~400W. And those power parts use 2 large transformers, the power amplifier part uses two pairs of Toshiba celebrities C3280, A1301, each channel only standard 80W models, but the best choice. The power supply of this kind of amplifier is abundant, and the positioning and strength of the instrument are better when the music is dynamic. Therefore, when selecting the power level of the power amplifier, it must be seen whether the power supply part and the output power circuit part are properly matched. Otherwise, if the volume is turned on, serious distortion due to insufficient power supply may occur.
2, the pre-stage circuit Domestic power amplifier pre-stage circuit can be roughly divided into two types of hybrid and integrated circuits, transistor discrete components have been rare. The pre-amplifiers of the commercially available power amplifiers are mainly integrated circuits, and the better ones are NE5532 and NE5535. There are also preamps that are used in the form of ordinary op amps such as TL082, NE4558, and LF353. However, this type of power amplifier is gradually eliminated due to the slow conversion speed and high noise of the preamp. In addition to the op amp, the key depends on how the preamp power supply is provided. Some are separately powered, and the other winding of the power transformer is subjected to rectification and filtering, so that the performance of the preamplifier is better. If the front stage of the op amp is powered by the power servo circuit developed by Panasonic, the signal-to-noise ratio of the pre-stage and the resolution of the music are higher, which is better than using a simple three-terminal regulator or sharing with the amplifier stage. The group power supply is supplied to the front stage of the power supply via a simple diode regulator.
3, signal channel Some power amplifiers use light touch electronic control signal selection at the beginning, although these switches look good, the touch is also good, but most of them use analog switch integrated circuits such as CMOS CD4066 as channel selection, CD4066 distortion is 0.1% Between ~1%, if the performance is not good or due to factors such as power supply, the distortion and noise may be higher, so the power amplifier produced by this type of circuit has a distortion of 0.001%, which is generally virtual. Therefore, some high-end power amplifiers still use traditional mechanical selector switches. As long as the contacts are gold-plated or silver-plated, the reliability of the contact can be guaranteed. Of course, there are also power amplifiers controlled by electronically controlled relays. These types of power can meet the requirements in terms of aesthetics and performance, but the price is higher.
4, the function of a power amplifier of about one thousand yuan, if the screen display, reverberation, surround, karaoke and other functions are taken care of, then its investment in the power amplifier circuit and the pre-stage circuit must be small, which loses the focus. Generally, a power amplifier of about one thousand yuan is best not to have too many functions, because the effect of these too many functions is only general, and the sense of hearing is not ideal. In addition, there is a certain interference between the circuits, so the power amplifier is still simple and simple.
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