Superpower Output Impedance
compared to newer regulators

Belleson's newest SPX regulator was multiple years in development, and designed to have the lowest possible output impedance while keeping the circuit fast and stable.

How does Superpower compare with other voltage regulators? See these oscillograms and judge for yourself. Test notes are at the bottom of the page.

Why is low zout desirable?

Output impedance, or zout, is a small signal measurement of a regulator's ability to deliver current while vout remains constant. Any deviation from constant represents a voltage drop across the output impedance due to the AC excitation current from the output.

In this test, a 10mA AC current is pulled from the regulator, as frequency of the current is swept from 20Hz to 200kHz. The AC voltage appearing at the output of the regulator represents its output impedance, where zout=vac/iac.

If you look at a power supply as a source of current from a fixed voltage, any impedance at the power supply output is in series with the load impedance being driven by the supply. That load is, for audio, typically one or many amplification devices. The supply impedance and the load impedance form a voltage divider, so as the load requests current from the supply, the voltage at the load will change by the amount zout * iload.

Thus lower supply zout delivers fundamentally better supply voltage regulation. Watch the first three minutes of this video from Texas Instruments to learn more.

SPX78SPX78 10mA output impedance

Belleson's SPX78 has very low zout at audio frequencies and increases gradually to 50mΩ at 200kHz.


Sparkos SS7812 10mA output impedance zout for the Sparkos SS7812 grows to 110mΩ at 110kHz then decreases slightly toward 200kHz.


LM7812 10mA output impedance The LM7812 with high impedance around 10kHz and its noisy. zout is set mostly by the output capacitor.


LT3045 10mA output impedance

The LT3045 from Analog Devices has a Zout that increases in a slight bow up to 60mΩ at 200kHz.


TPS7A4700 10mA output impedance The TPS7A4700 from TI has a bloom in the audio band, where zout is about 200mΩ at 10kHz.

Dexa/NewClassD LC7812 UWB Mk2

Dexa LC781  UWB Mk2 10mA output impedance Relatively high zout with a peak in the audio band up around 180mΩ , and visible noise.


Measurements are taken in the same test socket, with the same input stimulus and output sense for all devices. Measurements may differ from those you see in manufacturers' data sheets because of different setup, e.g. input or output capacitance, placement of sense device, wire lengths, etc.

Voltage is amplified by 1000 and graphed on an oscilloscope. You can see frequency change across the horizontal axis at 20kHz per division.

The top trace is output current as measured with a Tektronix current probe amplifier set to 10mA per division. For some regulators the change in vout is too low to be useful so we fed it through our noise amplifier to give it a gain of 1000. Thus the bottom trace is 1000 x regulator Vout.

The LT3045 and TPS7A4700 are both surface mount monolithic devices that require a PCB to allow them to be plugged into a TO-220 style test socket. The tested devices were, when purchased, mounted on a PCB with MLCC capacitors already connected. Replacing the MLCCs with tantalum on the TPS7A4700 PCB significantly improved performance, and the measurements you see here are with 10µF tantalum.

It's possible that zout graphs of the lowest measured parts have some error due to feed–through in the test fixture. Thus zout could be lower than we measured.


This site is being gradually updated. If you have any problems please email

The Industry Standard SPX

Order now from our store.

  • 5V to 30V output
  • World's lowest output impedance
  • Superb ripple rejection (135dBV)
  • Instant step response
  • Extreme low noise
  • TO-220 footprint
  • No thermal pad needed!

High Voltage!

Tube lovers—SPHV is BACK!

  • Variable output 5V to 450V
  • Up to 500mA output current
  • Super low 0.5V drop-out at 100mA
  • Small TO-220 footprint!
  • Low output impedance
  • Fast response
  • Low noise

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SPHP—1000 Watts for your music server!

SPHP, a 10A Superpower with adjustable output voltage from 5V to 100V

  • Same low noise
  • Same blazing step response
  • Same great ripple rejection.
Just lots more current and much higher output voltage. For sale on our order page See more information in the data sheet here.

Build a power supply

A PCB and parts list for building a compact dual positive or positive+negative power supply are on this new page.

Transformer Calculator!

Use the Belleson Transformer Calculator to calculate the minimum Vrms voltage of a transformer for your Superpower based supplies.

It's Official

We're proud to announce the U.S. Patent and Trademark Office has granted patent 8,294,440 to the Superpower design.

Use the Superpower regulator in...

  • Headphone amps
  • DACs
  • Buffers
  • Clocks and reclockers
  • Preamps
  • Microphone preamps
  • Phono stages
  • Phono motors
  • Tube preamps and input stages
  • Line powered guitar effects boxes
  • Anywhere an extremely clean, quiet, dynamic power source is needed