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目前使用的电子管有线广播扩大机的整机效率仅30%左右,且有电路复杂、造价高、电声质量欠佳、使用维护不方便等缺点。晶体管脉宽调制式扩大机具有效率高、线路简单、造价低、电声质量指标优异等优点,它应该成为旧式电子管有线广播扩大机更新换代的产品。本刊今年第六期刊登的《高效有线广播扩大机》一文(后面简称前文),在这方面作了初步探讨。本文电路是有别于前文调宽脉冲输出解调电路的另一种电路形式,它省掉了价格高、体积大而笨重的音频输出变压器。如果直流主电源由市电220V 经桥式整流直接取得,也省掉电源变压器的话,那么整个扩大机不但体积小、重量轻,而且造价也很低。
The currently used tube radio cable amplifier machine efficiency is only about 30%, and the circuit complexity, high cost, poor quality electro-acoustic, inconvenient use and maintenance shortcomings. Transistor PWM amplifier has the advantages of high efficiency, simple circuit, low cost, excellent electro-acoustic quality index, etc. It should become the replacement of old-style tube cable broadcast amplifier. The article published in the sixth issue of this year, “Efficient Cable Broadcasting Amplifier,” a text (hereinafter referred to as the preceding), made a preliminary discussion in this regard. This circuit is different from the previous pulse width modulation output demodulation circuit another form of circuit, it eliminates the high price, bulky bulky bulk audio output transformer. If the main DC power supply by the city directly through the bridge rectifier 220V, but also save the power transformer, then the entire amplifier is not only small, light weight, but also low cost.