Power Supplies

Dual Polarity Unregulated Power Supply for Audio Amplifier



The most common source of power for audio power amplifier is the unregulated power supply for its simplicity, good performance, and reasonable cost. The basic parts of an unregulated power supply are the transformer, diodes, and capacitors. The main draw back of an unregulated power supply is voltage fluctuations with load and power mains fluctuations. The power supply project presented here have current limitations, 24VAC @100VA, but the theory of operation is the same as any higher voltage or current power supplies. This power supply project can supply power to any one channel audio power amplifier project presented in this website.

The AC line votage goes into the primary of the power transformer through a fuse and a switch. The AC is then transferred to the secondary winding by magnetic induction to whatever voltage your audio amplifier requires. The AC in the secondary winding is converted by Br1, a bridge rectifier, to a pulsating direct current. C1, 2, 3 and 4 are large value filter or reservoir electrolytic capacitors that smoothes out the low frequency fluctuations coming from the bridge rectifier. The voltage across these capacitors is now DC with a few millivolts of ripple on each rail. C5 and C6 are film capacitors that reduce rail high frequency noise. R1, L1, R2 and L2 are power ON indicators and may be omitted if you prefer.

Increasing the capacitance value of the filter/reservoir capacitors reduces the ripple in the power supply's DC rails. It would also improve the low frequency response of the power amplifier and in my opinion, will be a much cleaner, heftier and meaner sounding audio amplifier.

power supply project-schematic

 Schematic Diagram of Dual Polarity Unregulated Power Supply Project

power supply bottom copper layer-page-001 (1)                           power supply silkscreen layer-page-001 (1)

                              Bottom Copper Layer of Power Supply Project                              Silkscreen Parts Placement Layer of Power Supply Project


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Basic components of building an unregulated power supply for audio amplifiers.




  +/-54VDC SMPS


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The Switch Mode Power Supply project puts out +/-54VDC at about 5A per rail, enough to power one channel of any audio amplifier projects that requires higher voltage presented in this website.

I housed the 2 power supply modules in an aluminum project enclosure, added banana jack binding posts for the outputs, a power switch and a 2-wire LED panel voltmeter to display the output voltage. For continuous operation, I highly recommend adding a fan on top of the modules, as shown in the picture. For more information about this power supply please read XL280-AC-DC-Series-Power-Supplies-705501. Enjoy!


hVWarning! Always be careful when working with power supplies! This website is not responsible for any injury or damage that might occur while building or testing this project.