音響要吃電,電力公司的交流電源送來的110V是個sine波;音響內需要的是?直流,一條水平線不變的電壓。由這變動不斷的110V sine波經過整流子與濾波電容變成直流電壓,實際上是,微微抖動的電壓,後面設備吃掉一些,電壓就掉下去,等到下一次60Hz或120Hz的sine波的峰值抵達時,才又充上去,你可以想想,二萬的音響 vs 二十萬的音響,那直流電壓的微微抖動是同一等級嗎?顯然便宜的對電源敏感的多,電容少,濾波能力差;
The World's Encyclopedia of Recorded Music in 1952 cites only two recordings of The Four Seasons – by Molinari and Kaufman. By 2011, approximately 1,000 recorded versions have been made since Campoli's in 1939.[citation needed]