Externally-Controllable +24V Power Supply
For the BIAMP AudiaFLEX in my Home A/V System

Devin R. Ott
Designed & Constructed – October 2012

Description:

Well aware of my strong background in circuit design / hardware design, my boss at Hoppmann Audio Visual gave me a top-of-the-line BIAMP AudiaFLEX digital audio processor that wasn’t working. I was not surprised when I opened the chassis to find a failed universal power supply.

I custom-fitted a 24V@3A external power supply inside the AudiaFLEX, along with this custom control circuit, enabling third-party power on/off switching via 3.5mm input port on rear panel.

· Power on/off is controllable via CMOS/TTL digital logic, or contact closure (input mode is selectable via DIP switch).

· When nothing is plugged into the control port, the system operates in “ALWAYS ON” mode and sends power through to the motherboard.

· When a control cable is plugged into the 3.5mm jack, the circuit enters “EXTERNAL CONTROL” mode wherein the system default is POWER OFF, unless a high logic level or contact closure is sensed on the control input pins.

· A single bi-color LED [on rear panel] indicates power status: GREEN=ON; RED=OFF.