Monday, October 3, 2022

1W Guitar Amplifier in a 60's portable radio case

 I've found a junked 60's portable radio by Harmonius, which it used to be a small Italian manufacturer.

I like the shape of the radio, so I decide to use it.

Unluckily the back case of the radio is broken, so I have to replace the back with a wooden wine box case.
Have to cut the front retain plastic on both side, and glue a couple of pieces of wood to make the front fit the wood.
Then I paint the wood and apply wax.

Inside I've put just a little bit of filter fabric of a cooker hood.

I've reused the original PCB as support for the supply, and for the tone control.

Also, I've reused the main transformer, which is a 230V to 12V AC. The supply is regulated to 9V using a 7809 with an heatsink and a couple of capacitors.

The main amplifier board is build araound a LM386 IC. The schematic is based on the "Ruby Amp", with a little bit of mods.

A tone control, mounted on the tuner pot, is added.

The volume is mounted where the original radio volume was.

Two selectable buttons where used for: Clean/Overdrive selector and Overdrive/Distorsion selector. This last one is enable only if the Overdrive channel is selected by the first switch button.

The original speaker was fixed using a little bit of casting plastic.

The end result was a mini 1W amplifier that is pretty looking.

Last but not least, I've found a bounch of germanium transistors inside this radio, I'm happy I've saved those two from junk.


  • read risk disclaimer
  • excuse my bad english