Day of rest eh?

Ah Sunday. Day of rest. So I shall.

Then I decided to dismantle the PA system for my Dolby Digital setup. I bought it cheap (never can resist a bargain) and it works fine, except that it hums along with the soundtrack at around 50 Hz. The way I see it, there are four reasons why amplifiers hum (other than the fact that they don't know the words - ho ho), either the inputs are not properly earthed, the device itself is not properly earthed, the power supply is not properly smoothed or the box is picking up hum from inside.

Of course the answer to these complex technical problems is to "take the back off and poke around a bit". By the way, don't try this yourself. In the UK we have 240 volts coursing down the mains cable and this can seriously damage your lifestyle (and even end it). I read some advice (which may be bogus) which is that when messing with things which might be live you should keep your left hand in your pocket. This is the hand which is (allegedly) wired through your nervous system directly to your heart. Mains up this hand will go through your heart and probably stop it. Apparently the right hand is wired differently (and somewhat less life threatening). This is a bit of a pain for any southpaws out there and it may not even be true, but I always do this now...

Anyhoo, got the back off my nice little subwoofer revealing the true horror which lies within. And found out why it is so cheap. The standard of construction was horrid. And it had all been covered in glue. And the designer had located the mains transformer (a device which works by pumping out a magnetic field) right next to the input connectors (which are designed to transfer tiny signals). Of the four possible causes of humming, I've got three of them. I hate bad design. I see is as a form of cheating. By simply turning the board the other way up, and putting the speaker connectors near the transformer the idiot designer could have removed most of the problem. By putting bigger capacitors on the power supply he could have removed just about all the rest. And then by adding an earth wire we would have had a squeaky clean signal. Instead the whole thing was around ten pence cheaper to make and didn't work very well. Hmmm. I think this will be a case where we have to use a dustbin to solve the problem. Should have saved up and bought the Sony one....