There are certain aspects of my mythtv PVR system I’ve been unhappy with. They are:
- Low hum on all recordings. “hoommmmmmmmmmmmmmm”
- Bad video output — the display flickers and you can see pulsating waves
Hums are usually a sign of an Audio Ground Loop. If two electronic components are at slightly different potentials, usually because they are plugged in to different sockets, an audio cable will actually create a complete circuit. A small amount of charge flows between the two components, and you hear a hum out of your speakers. Radio Shack makes a cheap doohickey called a Ground Loop Isolator that solves the problem.
Unfortunately whenever I tried using the Ground Loop Isolator, I would hear a different, even more annoying squeal. So for a while I lived with the hum. Today, after some experimentation, I discovered the the squeal occurs because the onboard sound jacks are close to the monitor plug. If I disconnected the monitor cable, the squeal would change! So I bought a 24$ sound card on clearance, positioned it far away from all the other jacks, and now there are no annoying noises coming out of the speakers.
As for the video problems, my PC->TV converter was the cheapest possible model. The next version up from the same company solved all the problems. The one I have now is a Grandtec (like my old one) but it has a little remote, supports more resolutions, and outputs to component as well as svideo. It seems scan converters is one place where it does no good to get the cheapest option (unlike 24$ sound cards).