Mini Project: Guitar Amplifier (old!)

Playing guitar and electronics have been two of my favourite things for a long time now. When I was about 14, I combined these two for the first time and built a pretty simply 32W amplifier. While the design is super simple, it actually has a really nice clean tone and does not distort the sound at all. It’s capable of diving an 8 ohm or 4 ohm load. Today I decided to give it a bit of a clean and check if it still worked.


Only a volume knob, an input jack and a power switch on the front


A big heatsink and the speaker connectors on the back

It was based on a book I had, called Audio Amplifier Projects by R. A. Penfold.

The circuit is super simple. It’s actually very similar to the example circuit taken from the datasheet of the main amplifier IC – the TDA2050 (now obsolete).

Screenshot from 2017-09-21 00-36-15.png

Application circuit taken from the datasheet for a single supply rail

The circuit is powered from an unregulated 45V which is generated from the mains using a toroidal transformer, rectifier and smoothing cap. Because it is powered from mains, it has to be in an enclosed, grounded box.


Internals of the box

At these relatively high powers, the TDA2050 can get very hot so a big heat sink is needed.

While the design is very basic it does actually sounds very nice and it brought back fond memories. I remember my dad shorting the large mains capacitor with a pair of pliers in order to discharge it – they are still slightly bent at the end from the resulting bang.

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