OK, I admit to cheating a little bit with the title. The Amp in a Can is not really a tube (valve) amp at all, but rather a cheap and cheerful portable guitar amp housed in cardboard tubing that weighs less than 200 g (7 oz).
Electromechanical engineer Wayne Tubby made his first Amp in a Can prototypes a few years back while attending college. Though they're no longer fashioned from old rice pudding tins that spawned the name, the moniker stuck. A few design revisions later and the portable guitar amp is now made from 80-mm (3.14-inch) diameter reinforced recycled cardboard tubing with plastic end caps and a handy strap.
The shape of the amp is said to lend a little more bass and volume to the output from the single 2 W speaker hidden within the tube. Tubby told us that one of his prototypes did have stereo speakers, but the sound was better with just one so the idea was abandoned.
Sound from the proprietary amplification circuitry is controlled via off-the-shelf volume and tone knobs to the front. There's no gain or onboard distortion that you might find on mass-produced pocket amps, but that's not necessarily a bad thing.
It's powered by a 9-volt battery and you plug in the guitar via a 0.25-inch audio jack round the back.
In order to raise enough funds to finalize the product and make it ready for shipping out to buyers, Tubby has launched a Kickstarter crowdfunding bid. Unusually, there's just the one pledge level available at £23 (US$34), which will secure one of the first Amp in a Can units off the production line (assuming a successful conclusion to the campaign).
The pitch video below shows the portable amp in action.