![]() ![]() LM317 is almost always stable, even without any Cout. They need some series resistance to be stable. Back then capacitors had much higher ESR and ceramic capacitors were nowhere near uF range. They are only required for high voltage operation (such as +/- 25V) or capacity much bigger than 10uF.Ĭhoosing output capacitors is the tricky part. I ommited Cadj discharge diodes as they are usually not mandatory. I'm open on any suggestions or improvements.įirst of all I would like to thank you for your input. Latout PDF printed at A4 paper should be 1:1 of board size.Īll required files such as schematics, BOM and gerbers are attached to post. That means cheap PCB fabs like JLCPCB can be used. ![]() Besides being indicators they run at relatively high current, providing constant load to regulators which keeps low output impedance.īoard measuers 100mm x 45mm. Output voltage can be changed by choosing diffrent zener diodes.Ĭadj capacitors are of course present, something from range 10-47uF is recommended. By default 13V zeners yelds about +/- 14.5V at output with less than 10mV diffrence beetwen negative and positive rails. Dynamic resistance of zener diode is lower than required resistor which should result in lower output noise. Instead of using more common voltage divider to set output voltage I decided to use zener diodes. Regulators are protected by D3 and D4 diodes. That would push costs even lower in tradeoff of small performance drop. If desired, inductors can be replaced by 0-10 ohms resistor or even shorted. Those wall warts are cheap and easy to use as there is no contact with potentialy dangerous mains wiring. Board can be powered by AC-AC wall wart or transformer. Good old LM317 and LM337 regulators and half wave rectifier. Basically, this is PSU part of my headphone amplifier. The idea of making this project came after seeing this thread. Heres my attempt to design universal, quiet and relativly cheap power supply for those needs. Lots of audio equipment requires regulated, low noise power supply. ![]()
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