Prevent humming between sound card & stereo
If you connect the sound card on the PC with the stereo, it often comes to a more or less strong hum. How to prevent this humming loop between sound card and stereo is explained in this tip.
The reason: The ground and protective conductor of the devices are connected to each other, and if the devices hang on different sockets or even different circuits, there may be potential differences. If now closed by the signal line between the sound card and stereo the ground loop, creates a so-called ground loop; a compensating current flows through the ground line, which then influences the useful signal and thus causes the hum.
- This can be remedied by either eliminating the potential difference or interrupting the equalizing current (and thus the hum loop). This can be done in several ways:
- Connect PC and stereo to a common power strip. Often this is already enough to eliminate the potential difference.
- In the line between sound card and stereo insert a low-frequency transformer (NF = low frequency), this is in stores and separates stereo and sound card galvanic, the ground loop is interrupted. A NF transformer is technically nothing more than a transformer that is optimized for the transmission of audio signals.
- Sometimes the stereo is connected to an antenna system, and the hum loop is created via the antenna socket. You can test this by pulling off the antenna plug. If the hum is gone, this is the cause. Also in this case helps a LF transmitter in the signal path between the sound card and stereo system, or you buy in stores a so-called sheath current filter; this is nothing more than an RF transformer (HF = high frequency) and thus a transformer optimized for RF signals, which is plugged between the antenna socket and the antenna cable and in this way interrupts the ground loop.
- Another theoretical possibility is to connect each device individually to the power supply via a isolating transformer. But this is not a sensible solution for cost and space reasons, because you need a separate isolation transformer for each device. :-)
Anyone who, of course, as a proud owner of a sound card with optical output and a stereo system with optical input can be lucky, will not know such problems.
ATTENTION! A final warning: The tips to manipulate the protective earth, which one unfortunately reads from time to time, you should quickly forget and under any circumstances apply, because manipulating the protective conductor always means LIFE!
