Holtek 公司的HT8972是回声/环绕声效果处理器，设计用于各种音频系统如卡拉OK，电视，音响设备等。芯片包括了前置放大器，VCO或压控OSC，40Kb SRAM，ADC和DAC以及延迟控制逻辑。HT8972的工作电压从4.5V 到5.5V，回声模式的噪音为-85dB，失真为1%，环绕声模式的噪音为-90dB，失真为0.2%.本文介绍了HT8972的主要特性，方框图以及回声模式和环绕声模式的应用电路。

The HT8972 is an echo/surround effect processor. It is designed for various audio systems including karaoke, television, sound equipments, etc. The chip consists of a built-in pre-amplifier, VCO or Voltage Control OSC, 40Kb SRAM, A/D and D/A converters as well as delay time control logic.
Its built-in 40Kb SRAM can generate delay time effect and can control the delay time value through the external VCO resistor.
The VCO circuit can reduce external components and make it easy to adjust the delay time.

HT8972主要特性：
Operating voltage: 4.5V~5.5V
ADM algorithm
Low noise
Echo mode: _85dB
Surround mode: _90dB
Low distortion rate
Echo mode: 1%
Surround mode: 0.2%
Built-in 40Kb SRAM
Automatic reset function
16-pin DIP/SOP package
HT8972应用：
Television
Karaoke systems
Video disc player
Sound equipments



图1。HT8972方框图
应用电路
回声模式：



环绕声模式：