Mini Amp

Constructomaton managed to find this fine 1940s bakelite radio extension speaker whilst rummaging about for spare parts in one of his local antiques centres.  

This was crying out to be converted into a guitar amp.  I was please to find that the speaker still worked fine, so all I needed to do was build an amp circuit and a jack input.

There are loads of schematics for mini-amps online (particularly on runoffgroove.com) and they're mostly pretty simple to build as they don't involve many components.  

However, I'm not an electronics whizz, and finding suitable parts in the UK can be a bit tricky and expensive, so I ended up ordering a printed circuit and parts from rubyamp.com.  

It comes with everything except the speaker, so you just have to wire it up and solder it all together.  It has gain and volume controls, and is powered from a 9volt battery.  You can use this circuit to drive pretty much any size of speaker, or even use it as a pre-amp and hook it up to a cab.

I added an LED to the circuit (as per the instructions in this PDF from generalguitargadgets.com) mainly because I thought it would look cool.  Unfortunately, I hooked it up wrong so that the circuit was always on, so I also had to add a switch to cut the power.  

 

 

My dad, Constructomaton Senior, let me use his bandsaw to cut out a new back panel for the amp out of plywood, so I could affix the input jack, LED, switch and gain control (the original back panel was a fairly battered piece of cardboard).  I removed the original 1940s volume pot as it was a bit worn out and replaced it with a new one.  

 

That's it - a pretty simple project all round.  The amp sounds great and goes from clean to a nice bluesy crunch.  It's pretty loud for its size - I've put a mic in front of it and used it with a full band and it held it's own just fine.