[written 2018]

Proper power supplies are expensive.

• Cheap switched mode supplies are often noisy. If you’re working on audio/RF stuff, the ripple of a switched mode supply is unhelpful.
• Linear supplies are expensive and inefficient

I decided to make my own, since I wanted both linear and switched supplies

I figured the cheapest rugged chassis I could easily get my hands on was a stereo audio amplifier.

I picked up a faulty old Kenwood unit on ebay for less than £10. I bought something where I could reuse the transformer and heatsink.

The original amplifier

For the switched mode supply, I used this buck converter that I’ve written about previously; it has current limiting and a serial command port, making it easy to feed commands from an Arduino.

For the linear supply, I used a LT1083.

A 24V mains SMPS unit powers these two output stages normally, but there’s the option to switch their input to the 40V rectified transformer output if higher voltage is required. In general I tried to make the whole thing from fairly modular blocks which could be connected as required.

An Arduino mega powers the UI on a small TFT screen, sends commands to the buck converter, reads the front panel rotary encoders and samples some external ADCs.