Hifi Regulated Dual Power Supply

Using only an AC wallwart, giving ultra-low ripple

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I made a new version of this PSU:

This is a +-/- 15 volts DC, regulated dual power supply that has been designed for hifi purposes. It is powered by a single 15-18VAC wallwart supply, and has a very low 0.1 mV (RMS) ripple.

The wall adapter can of course be substituted with an AC transformer, 15-18VAC.

The PSU is originally built for the AudioKarma CNC Phono Stage and is equally useful for any other hifi equipment, be it discrete or opamp based.

Like the AudiKarma CNC Phono Stage, this PSU is also no-nonsense. AC in, a voltage doubler for the rectified voltages (both positive and negative), LM317/337 voltage regulation and filter capacitors.

A tiny PCB and ordinary off the shelf components really is all you need to get a PSU fit for hifi applications.

The 76x46 mm Printed Circuit Board is available at my Tindie Store:

This PSU takes a single 15-18VAC input and gives dual 15VDC output.

It is dead simple, has excellent performance, and consists of the following stages:

  • Single 15-18VAC input
  • Two half-wave rectifiers
  • Voltage doublers
  • LM317/337 voltage regulators
  • Filter capacitors
  • +/- 15VDC and ground output.

By using a wallwart, there is no risk of electrocution or fires.

The PSU performs superbly. Used together with the Muffsy Phono Preamp PP-2, it has only 0.1 mV ripple on the DC output. Well below the Power Supply Rejection Rate (PSRR) of any operational amplifier, and very suitable for discrete circuits.

The PSU gives up to 100 mA of current when used without heatsinks. That's enough to power four phono stages.

Mount heatsinks on the LM317/337 components and replace the 10R/1W resistors with 4.7R/1W if you need more current than this.

If you need exactly the same positive and negative output power, match the 300R and 3k3 resistors. With no matching, you can expect a maximum deviation of ~10 mV.

These AC to AC wall transformer are suitable for use with this PSU:

120V Input:

230V Input:

  • 6 × 1N4004 Discrete Semiconductors / Diodes and Rectifiers
  • 2 × 300 ohm 0.25W metal film resistors, 1% tolerance
  • 2 × 3300 ohm 0.25W metal film resistors, 1% tolerance
  • 2 × 10 ohm or 4.7 ohm 1W resistors
  • 4 × 2200 uF Electrolytic Capacitor, 35 volts or higher

View all 11 components

  • 1
    Step 1

    Just keeping this very simple, since there are so few parts:

    1. Mount and solder the components, snip off the leads
    2. Connect a 15-18VAC wallwart adapter to the pins AC-1 and AC-2
    3. Take +/- 15VDC from the pins +VE, -VE and GND

View all instructions

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skrodahl wrote 04/23/2015 at 06:45 point

I have added a few sources for AC to AC wall transformers. They can be a bit hard to find.

Please post your source in the comments, if you have one.

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