Okay, last lap for the actual build. But there's more to come in this blog. Over the next few installments I want to take a brief look at some of theory behind what makes the CBA tick.

But for now, I'm going to post tonight's little diversion.

I want to give Peter something that is pretty much self-contained so it was always my plan to add a speaker cabinet to the package. And this would also be built into a cigar box.

So, we have a speaker from a car stereo system, simply because it's rated at 30 watts RMS and is small enough to fit in the box I've got to hand. And you can see the box and socket in the pic too.

Not only do I prefer my amps to be old school and use retro technology, I'm the same about my wristwatches. And this spring-powered beast didn't deserve to be magnetised while working on the speaker so it had to come off.

So we find a centre point by drawing across the diagonals.

Then measure the mounting diameter of the speaker. There is a cutting template in the box, but I always like to check anyway.

Out with the trusty old pair of compasses.

And then I hit it with a large hole saw. No pics of that sadly.

Speaker mounted and socket soldered into place.

Time for testing (with the lights off so you can see the glow).

And with the lights on so you can get a clearer view.

It sounds better than I expected, but it's more an exercise in completeness. The amp sounds stunning through a big cab, so I'm guessing it won't be too long after Peter gets back to Australia before he sources something more appropriate. Oh, and tonight's "ah bollocks" moment... I've fitted the speaker grille upside down. There's lettering that reads "Mutant X" on one of those curved sweeps and that kind of gives it away. And it was a sod of a job getting the nuts on the bolts too! Still, I've got until 27 October to correct that little error though.