AV擴音機與前,後級@@?

前級的作用是將訊號作第一次, 用作接駁播放訊號的器材, 如CD, DVD, 唱盤等等; 後級的作用是將前級的訊號再次放大, 放大到能推動喇叭. 這個只是最簡單的解釋, 當中還有其他的原因及技術問題, 足以寫一大篇文章.

因為從CD 機 (或DVD, 或唱盤) 播放出來的訊號是十分細, 如果從CD 直接放大到能推動喇叭, 中間要放大的倍數太大, 簡單說是器材做不到. 所以從CD 機出來的訊號必需先經過前級作第一次放大 (例如是10 倍), 之後再傳到後級作第二次訊號放大 (例如又是10 倍), 即是從CD 出來到喇叭能播放, 訊號是放大了100 倍 (前級10 倍, 後級10 倍), 如果分為前級和後級, 則每級的元件只需處理放大10 倍便可以. 但如果以單一元件來說, 便需要單一元件處理放大100 倍. (以上只是舉例, 後級的放大率不會10 倍這麼細).

AV 擴音機只是將前級和後級放在同一個機箱內, 再加上AV 用的解碼器 (如Dolby Digital, DTS, etc), 所以在機箱內其實是分為第一級訊號放大, 和功率放大 (第二級放大) 的部份. 大部份會將第一級放大的元件和功率放大的元件距離盡量拉開 (如一個在左邊, 一個在右邊), 以減低兩者間的互相干擾, 這亦是為何高級機種會將這兩部份分為獨立的前級和後級的其中一個原因.

前級 (Pre-Amplifier or pre-amp), 後級 (Power Amplifier or power-amp) are mainly used for some high rank Hi Fi users.

In general, the signal from source (like CD player, DVD player) too small to drive a loudspeaker therefore amplifier is used to amplify the signal for listen.

The amplification ratio for amplifiers cannot be too large since this may result for some distortions. Therefore the high rank amplifier will separate the amplification into 2 steps, which is the main reason for using pre-amp and power-amp.

AV擴音機 (AV-Amp) - since nowadays more and more AV equipment are available in the market, like CD, DVD, Blu-ray disc player, iPod; and the home therate system was introduced (like DTS5.1). AV-Amp become widely used as this amplifier have more input channels and can support for 6 (DTS5.1) to even 8 (DTS7.1) loudspeakers. If you are not looking for some super high performance, AV-Amp can replace the Pre-Amp & Power-Amp. However, some Hi Fi lovers do not like AV-Amp as they believe the sound performance is not as good as the combination of Pre-amp & Power-Amp.

Hope you now have some ideas.