Power Supply Design
Key features of the power supply:
- 35A full wave bridge rectifier, mounted external to board using chassis as heat sink.
- 30,000uF electrolytic capacitance per rail, configured with 10,000uF at bridge followed by .1 ohm inductive resistor, followed by 20,000 uF (to reduce ripple).
- Other decoupling via .1uF polyester and 1uF metalized polypropylene capacitors to reduce high frequency noise.
- Speaker turn-on delay of 4-6 seconds, until circuitry has settled.
- PCB-mount encapsulated 12 VAC transformer and linear regulators generate +/- 12 VDC for op amps.
- Separate 12VDC source for relays. and on/off control switch/power on indicator.
- Double 100,000uF capacitors in series as DC filter on AC mains to eliminate possibility of DC-induced hum from mains.
- Use 20 ohm Ametherm thermistor in parallel with RC time-delayed relay to limit inrush current.
- Fuses on input and on each output rail for short circuit protection.
- 63VDC intermediate earth ground return (which is then connected off PCB to system star ground).