How to set SPX variable output value?

SPX17, SPX78 and SPX79 are available with variable output by adding a resistor here:

SPX78 variable When shipped, variable SPX has Vout=30V, so add a resistor to set the correct voltage before you connect it and power it on!

Fixed and variable output SPX, the only difference is if we add the extra resistor or if you add it. We add a thin film 0603 SMD, you can use a ¼W resistor of your technology choice. The additional resistor is in parallel with a 10k resistor so Vout change is not linear with resistance change.

Calculate Rset in kΩ as

Typical values are

Vout Rset Nearest
1% value (Ohms)
5 0 0 5
6.3 548.52 549 6.3
7 869.57 866 6.99
8 1363.64 1370 8.01
9 1904.76 1910 9.01
10 2500 2490 9.98
12 3888.89 3900 12.01
12.6 4367.82 4320 12.54
15 6666.67 6650 14.98
16 7857.14 7870 16.01
18 10833.33 10700 17.92
20 15000 15000 20
24 31666.67 31600 23.99
30 none none 30

You can use a potentiometer to set Vout. A 50k trimmer will adjust from 25.8V to 5V, a 100k trimmer will adjust from 27.7V to 5V. The trimmer is in parallel with a 10k resistor so Vout change is not linear with resistance change.

The king is dead,
long live the King!

SPX has replaced SPZ

  • Variable output 5V to 30V
  • World's lowest output impedance
  • Better ripple rejection (135dBV@60Hz!)
  • Faster step response
  • Same low noise
  • Same TO-220 size physical form factor
  • No thermal pad needed
Order now from our store.

Measurement Videos

We have a new page with videos showing how we characterize our (and others') voltage regulators in the lab.

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