Now who thinks that changing power cables makes a difference?
I certainly do.
I hear what Joel says. I come from an electrical / electronic system integration environment so please read what follows in that context:
IME some measures taken by some power cable manufacturers are indeed valid (but not all). Honestly designed aftermarket power cables aim to reduce the noise currents flowing between closely spaced pieces of equipment. These noise currents are induced due to stray capacitances, mutual inductances etc between boxes and may contaminate signals via the signal return wire in unbalanced equipment. Technical people, please draw an equivalent small signal circuit diagram with all parasitic effects included if you struggle with this concept.
Transformer balancing is the only method to completely eliminate this problem. Quasi-balanced (semiconductor circuits) are still be somewhat prone to noise currents with excessive radio frequency content.
I have measured these noise currents many times and they have frustrated me many times. Mixed signal digital and analogue setups are more prone to this especially with many boxes in close proximity.
If you are technical and understand the problem you will also see that the often quoted "miles of Escom wire" argument is really irrelevant.
I admit that I have never established the need for special power cables in a home environment. From above mentioned work experience (12 bit environment) it is not hard to imagine that noise currents may sometimes be a problem in a top flight home setup.
If an aftermarket power cord just adds gold plating to rip the customer off leave it alone and make your own. There are a number of DIY designs on the net, most of which employ sound principles.
Also, I WILL NEVER use the cheap standard interconnect supplied with equipment (the type where the screen is also the signal return or earth). Because, if the screen is effective, it will induce a noise voltage in series with you equipment's own signal. Interconnects with separate signal and signal return wires, covered by a screen connected at one end to the signal return wire are cheap enough and do work better, That is a technique often used in a system or instrumentation integration environment for connecting unbalanced signals. I have done it many times to reduce noise and EMI sensitivity. BTW don't mock directional cables, this last design feature is the main reason why better interconnects are marked with a directional arrow. It isn't the copper that is directional, it is just the earthing scheme...
Related:
WARNING: Do the following only if you are qualified to work with electrical equipment and know how to avoid electrical shock. If not, ask a competent technician or engineer to help you.
You can reduce noise currents with most double insulated equipment boxes (Jap and far eastern goods without an earth wire in the mains cable) by experimenting. With the equipment plugged in, measure the voltage between the equipment's signal return (eg on an output connector) and your mains earth (at the plug your equipment is plugged into) preferably with a scope. Swap the live and neutral around. Measure again. Keep the mains connection that gives you the lowest voltage. Do that with all your equipment. If you now connect your equipment less noise current will flow in the signal return wire between equipment. Be concerned if you see too much RF noise in the scope measurement. Semi-conductor circuits do no like RF contamination and RF filtering fails at some point. Maybe you need good aftermarket power cords ......
