The Z-Reg Voltage Regulator

A simple voltage regulator for low current audio circuits.


The Z-Reg is a very basic, very simple voltage regulator element that happens to work surprisingly well. Don't knock it 'till you tried it.

How it Works

A Zener diode generates a useful if somewhat noisy reference voltage. This is filtered and applied to the base of the pass transistor. The transistor will keep its emitter at close to the base voltage regardless of the voltage on its collector or the current flowing though the device. To the extent that it can perform this function, it acts as an ideal voltage source.

The limitations relate to the current gain of the pass transistor and its transconductance, neither of which are infinite. In practice though the regulator typically provides 40 dB of ripple rejection, and for op amp based audio circuits coupled with modest amounts of filter capacitors this is usually sufficient to remove all traces of power supply noise from the output signal.

Circuit Boards

The Z-Reg circuit is often made an integral part of the circuit it powers, for an example of this see the Sapphire3 headphone amplifier.

For general purpose use this standalone regulator board is intended to be paired with a transformer with 12 VAC secondaries. (The VSPS or Phonoclone power supplies, for example.) The output voltage is ±11 V DC. No heatinks are needed if the output currents are less than 50 mA. Up to 150 mA output current is possible if small clip-on heatsinks are attached to the pass transistors Q1,2.

The evaluation board is double-sided board and measures 5x8 cm.

RJM Audio Z-Reg

Download Schematic (BOM)

Boards are available, see the products page page for details.

rjm003.geo at