Band together

摘要

In the 1980s, I started a job with a company that produced high-end analog stereophonic-audio systems. One of the products was a system comprising a 200W amplifier, a tape deck, a turntable, and a 10-band graphics equalizer. The equalizer split the audio-frequency range of 20 Hz to 20 kHz into 10 bands, allowing users to individually adjust the level of each band, using vertically sliding controls, from -12 to +12 dB. In its stereo version, it had 10 bands for the left channel and 10 bands for the right channel. The position of the sliders represented the frequency response. Most graphics equalizers then used one coil or one inductor per band, but this one used operational amplifiers instead of inductors.