Apogee Advanced Stepped Gain

http://www.apogeedigital.com/blog/the-secret-being-mic-pre-technology?retarget_60day

gain與頻寬成反比，這招用多級放大，必要時才切過去避開單級放太大頻寬不足；
不過呢，這又多了一堆電路...電源要做好，訊號要乾淨...