Wild Blue Pixel
TIP OF THE DAY
Friday, February 4, 2011
Last time I gave you a taster of a no solder kalimba pre amp. Well now I'm going to give you a shopping list of the parts you'll need to build one. All of the parts are available either online or in store, and some of you may have them laying around at home.
Pre amp shopping list:
This setup will be unshielded and that could cause interference. A metal box of some description would be a good idea to hold the components.
Shielded, what's he talking about?
Our environment is full of radio waves. practically everything that runs from electricity can potentially put out radio noise. Amplifiers are pretty good at picking this noise up. I had a light switch that would make a loud click come from the amp as the contacts sparked, and of course mains wiring is infamous for causing interference and hum on amplifiers. Plugging in a lead to your kalimba just gives it a bigger arial to pick up more interference. The idea is that the signal wire, the one that carries the sound, is completely surrounded by other wire or metal so that it stops the interference before it can be passed to the amp. Wikipedia has a good article on cable shielding here:
In the picture at right, you can see that I have built the pre amp in to a small metal box and that the sockets and components are all connected, or grounded, to the box. That shields all of the components inside from outside electrical noise.
While you are looking for your components keep an eye out for a suitable metal box to put it in. I'll award a mystery prize for the most original if you would like to send me some photos!