Impedance issues are more of a concern when you are dealing with video cables (The ISF shows that video cable must provide a 75 ohm connection). For those of you not familiar with the ISF, they are the Imaging Science Foundation. The ISF is to video, what THX thinks they are to audio; the people that set industry standards.

The limiting factor in a cheap audio cable is all in the construction and available bandwidth. Bandwidth for audio would be the limiting factor for speaker wire (hence why smaller gauge wire is better), but because the interconnect is carrying a low level signal balanced construction the most important design feature. This is when the positive wire is exactly the same gauge as the negative.

The construction of a cheap wire is very different from a monster cable (or other premium cable). A high quality cable will have 2 wires of the same gauge twisted together, then at least 1 wrap of foil or copper insulation around the outside to resist interference. Monster uses a 100% wrap foil shield and a 95% wrap copper shield. In the cheap ones you have the main positive conductor running down the middle and the ground (negative) runs through the shielding (the few strands of copper wire surrounding the wire in the middle). There are 2 problems with this type of construction:

1) Because the sheild also carries the signal it actually acts as a dipole antenna (a source of interference)
2) The extremely low gauge wire used in the cheap wires will limit transmission (which would have a similar result to increasing resistance) in the case of a headphone output this will be a more noticeable difference as the output is amplified by the MP3 Player. This also explains why the dock connector on the iPod provides more powerful sound in the G.

Another problem with the cheap cables is the ends. Take a look at a cheap cable and a higher quality cable. The cheap ones are a stamped piece of tin, where as the better ones will be a machined end that creates a very tight fit (on the RCA side not the stereo mini jack). Also look at the pin that goes inside the RCA plug, you will notice a lot in the middle of a good end which also increases contact pressure. Ideally there will be contact all the way around the surface of the plug to maximize the connection and utilize all of the bandwidth available. Don't worry too much about the gold conductor thing, this is only there to resist corrosion and is over emphasized by sales people. Having the gold coating may result in a longer life for the cable, but otherwise provides little gain in performance.

If you have a spare cheap red and white rca cable around your house cut off the end and strip back the plastic a bit to look at the construction. I used to have a picture that shows a cross section of a cheap cable vs a monster cable, if I can find it I will post it later.

Edit: I need to proof read before I submit a post.

Sorry if this post was a little long and boring, but I think it explains the problems some of you have been encountering.

 

Nice explanation Christian. Good work.