MiniVol PGA2320 Volume Control

  
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MiniVol is my effort at a very simple volume control board based on the excellent TI PGA2320 volume control IC, which offers impressive specs and can operate over a range of -95. 5dB to +31. 5dB. It utilises a small Atmel AVR microcontroller to control the PGA2320, and gives the builder the option of using either up/down pushbuttons or a rotary enco
MiniVol PGA2320 Volume Control - schematic

der as the user interface. The microcontroller`s EEPROM is used to store the current setting between power cycles. Since the PGA2320 offers up to 31. 5dB of gain, a jumper is provided to limit the control to 0dB. No additional functionality is provided, honouring the KISS principle. An external ±15V power supply is required, such as my MiniPow. A dual-layer PCB design and firmware are available and free for DIY use. The PCB was designed to be small and modular, perfectly suited to a DIY amp or preamp project as an inexpensive and excellent-sounding alternative to a potentiometer or stepped attenuator. With two boards it can be used for a balanced configuration fairly easily (see build notes for details). SMD components are used almost exclusively, since the PGA2320 is available only in the SO-16 pacakage, and because size was a major design parameter. Parts cost without the PCB is about $25. If there is sufficient demand, I might consider offering boards and preprogrammed microcontrollers for sale. MiniVol requires at a minimum a ±15V regulated supply, which is further regulated by an onboard 78L05 to 5V for the digital control section. An external 5V supply could be used if desired, by tapping ground and Vcc at the U1 position. Onboard decoupling consists of 150 µF electrolytic in parallel with 100nF X7R ceramic for each chip on the digital supply, and 68 µF electrolyic in parallel with 100nF X7R ceramic for the ± analog...



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