Noise

This morning I awoke in Las Vegas at 6 AM and, after going downstairs for a cup of coffee, returned to my room to find I cannot use WIFI to connect to the internet; too slow. Okay, clever me, my phone has a hotspot feature so I turn that on. I can't connect my laptop to the phone's WIFI and it is three inches from the laptop. I have to resort to a tethered connection to make this work and even write this post. Now, you might ask, what's going on? It's called airborne pollution. There's perhaps only several times a year this form of pollution hits Las Vegas: when CES comes to town and the other big technology centric conventions. The pollution is caused from too much WIFI, the radio bands get saturated. This brings up the subject of noise pollution inside our equipment. Noise pollution caused by the power supply in our amplifiers and DACs; the same power supply that is the lifeblood of our amp's operation. Remember yesterday's post when I explained how we convert AC to DC? We pass the AC through a small and inexpensive component known as a diode. This innocent little gem is about 1/4" long and retails for perhaps ten cents. It's responsible for a lot of noise. Here's a picture of the little devil. The one I've shown is an industry standard known as a 1N4004. You use four of these to make your full wave rectifier, or you can purchase four of them packaged in a single container known simply as a 'diode bridge'. Every time the AC passes through this one-way gate it sends out a small burst of noise. The intensity of that noise is dependent on the amount of power we're asking of the power supply: more power, more noise. This noise can be dealt with but many designers pay little attention to it. In our equipment, for example, we take the time to place small 'snubbers' near these devices to squash the noise. Why would we do that? Because adding noise that gets into your amplification circuitry is audible. It makes for a grunge to the music that's not pretty. Tomorrow let's move forward to answer a number of questions about turning our rippled example of yesterday into a straight line.