It's not too difficult to make your own amps.
My first amp was made using another DeCecco tin. Pretty rough, but it works.
I buy a mono 2.5 W amplifier kit from Mindsets (part number PAC 2000), and adapt it a bit, wire it to a jack socket and a speaker, and Bob's your uncle. It runs off a 9V PP3 battery (not supplied with the kit, although you do get the battery clip with the kit).
Incidentally, if you've never been to the Midsets site, they sell a lot of really interesting stuff. You should go and have a look.
The kit costs about £7. It needs soldering, but it's not too hard. In the kit you get a component that acts as a switch in the circuit. That's not very useful if you want to control the power from the outside of the box, so you will probably need to buy a toggle switch (eBay again) that you can connect to the printed circuit board with wires. In the DeCecco tin amp (above) I used the switch from an old defunct PC.
The kit also has a 50k potentiometer component that is supposed to be soldered to the board, that controls the gain of the amp. But again, if you want to have a knob on the outside of the box that controls the gain, you'll need to buy a 50k potentiometer (from eBay, probably), and connect that to the printed circuit board with wires.
The gain control is quite neat. On a scale from 0-10, the low numbers give a clean sound, and the higher numbers give you some distortion. This is pretty clever for such a simple circuit.
For this amplifier kit you need an 8 ohm speaker that can handle 2.5 W of power. I bought mine from Amazon. They are 5W 8 ohm Aluminum Round Internal Magnet Speakers. They cost about £3 each.
Moving on from a tin, which is difficult to cut and is pretty flimsy, I thought about using cigar and other wooden boxes.
One of the problems I'm having at the moment is to find a source of boxes. If you use a cigar box it has to be large enough inside to accommodate the speaker and the electronics, and the PP3 battery. The one I used above measured 15 cm (wide) by 12 cm (deep) by 8.5 cm (high). That's about perfect. But I picked up that cigar box in Gettysburg when on holiday there in 2009, and I don't go there very often! I think I picked it up for nothing.
The other box in the gallery above cost about £3. It's made of balsa wood so it's very soft. You have to handle it with care as it will pick up any ding. There's no point telling you where I got it, as the company don't sell them anymore.
So if you know of a source of cheap boxes of the right sort of size, please let me know.
I've also started making my own pre-amps. This is pretty easy also. I use the mono pre-amp kits from Mindsets again (part number MAP 436), which costs about £2.50. This also runs off a 9V PP3 battery (not supplied in the kit). The kits are very simple, and if you have a rudimentary knowledge of soldering you should be OK.
I'm probably the world's worst solderer, and if I can do it, anyone can.
As in the amplifier kit, there is a gain knob component that you will need to replace with a 10k potentiometer if you want to control the gain of the pre-amp from a knob on the guitar.
Pictured here is the finished product. All you need to do when connecting this within a guitar is to have the pickup going to the pre-amp input, and the output going to the jack socket.
The reason I started making pre-amps was that the thin pickups I'd made had a lower output to normal pickups, so I thought I might put a pre-amp in the guitar to boost the signal before it goes out to the amp.
I can't really comment on how well this works as yet as I haven't really used it in earnest. When I do, I'll let you know.
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