Noise from grounding problems can almost always be solved by judicious use of transformers. However, the root of the problem is often the ground topology inside the audio equipment itself. There are some ways to reduce the potential for grounding problems when designing audio equipment:
1. Use a "low value" resistor (I use a 4.7 ohm 1/2 watt carbon resistor) between the "protective" AC grounds and the signal grounds. This is a very high resistance when compared to the resistance of the ground wires, so practically all of the voltage from the stray AC currents which cause grounding noise builds up across this resistor, rather than the ground wires. 2. In some cases, an audio ground can be actively driven by a unity gain op-amp stage. This allows it to provide a ground reference, but it moves the noise polution caused by the stray AC currents to the DC supply rails, rather than the audio ground. Usually noise rejection is much better in the supply rails. 3. Star ground topology is a time honored way of reducing the common resistance across which grounding noise can build up. 4. Use components and circuits in the power supply which reduce the stray capacitance which causes stray AC currents in the first place. For instance, a power transformer with non-concentric windings or Faraday shields. -- Timothy Stockman ------------------------------------------------------------------------ Timothy Stockman's Profile: http://forums.slimdevices.com/member.php?userid=8867 View this thread: http://forums.slimdevices.com/showthread.php?t=40112 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
