[animaal]

Up to now, I've never really believed that there was any logic behind the theory that cables could make a difference to sound quality.

Tonight, I was reading an article about how badly designed HDMI is. (What's the matter with HDMI).

Although the article does not focus on audio cables, it makes sense that much of it would be relevent to audio cables. This may be old news to everybody, but just in case anybody finds it as interesting as I did...

Quote:

There are a few considerations that start to cause real trouble: Time: electricity doesn't travel instantaneously. It travels at something approaching the speed of light, and exactly how fast it travels depends upon the insulating material surrounding the wire. As the composition and density of that insulation changes from point to point along the wire, the speed of travel changes. Resistance: electricity burns up in wire and turns into heat. Skin effect: higher frequencies travel primarily on the outside of a wire, while lower frequencies use more of the wire's depth; this means that higher frequencies face more resistance, and are burned up more rapidly, than lower frequencies. Capacitance: some of the energy of the signal gets stored in the wire by a principle known as "capacitance," rather than being delivered immediately to the destination. This smears out the signal relative to time, making changes in voltage appear less sudden at the far end of the wire than they were at the source. This phenomenon is frequency-dependent, with higher frequencies being more strongly affected. Impedance: if the characteristic impedance of the cable doesn't match the impedance of the source and load circuits, the impedance mismatch will cause portions of the signal to be reflected back and forth in the cable. The same is true for variations in impedance from point to point within the cable. Crosstalk: when signals are run in parallel over a distance, the signal in one wire will induce a similar signal in another, causing interference. Inductance: just as capacitance smears out changes in voltage, inductance--the relationship between a current flow and an induced electromagnetic field around that flow--smears out changes in the rate of current flow over time. Impedance, in particular, becomes a really important concern any time the cable length is more than about a quarter of the signal wavelength, and becomes increasingly important as the cable length becomes a greater and greater multiple of that wavelength.

 

[ericj]

Video is MUCH higher frequency and MUCH wider bandwidth

By orders of magnitude.

 

[jtizzle]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif Video is MUCH higher frequency and MUCH wider bandwidth By orders of magnitude.

HDMI carries both video and audio signals.

All of the same principles that apply to one, apply equally to the other.

 

[Quint]

Quote:

Originally Posted by jtizzle /img/forum/go_quote.gif HDMI carries both video and audio signals. All of the same principles that apply to one, apply equally to the other.

This is off-topic, but I LOVE your avatar. I saw Johnny five times in the '80s and once right before he died, and the guy, though the epitome of the word erratic, truly put on one of the most compelling shows I've ever seen. A hugely influential guitarist, as well. OK, back to our regularly scheduled thread!

 

[Duggeh]

Quote:

Originally Posted by jtizzle /img/forum/go_quote.gif All of the same principles that apply to one, apply equally to the other.

Mostly true.

 

[ILikeMusic]

Quote:

All of the same principles that apply to one, apply equally to the other.

No, they don't, or at least not equally. While these properties affect do all signals transmitted via a wire there is a dramatic difference in the magnitude of the effect based on both the amplitude and frequency of the signal being transmitted. The question is not whether typical audio-frequency signals are affected in some theoretical sense, but rather could the result possibly be audible to the human ear... and the answer to this is simply no.

 

[ericj]

Quote:

Originally Posted by jtizzle /img/forum/go_quote.gif All of the same principles that apply to one, apply equally to the other.

Yes, but the effect of these principles is several orders of magnitude greater for video signals than for audio signals.

If you really want to freak out about cable quality, go to the nearest university with an engineering department and read up on microwave RF transmission.

I'll wait here while you dream up wave-guide interconnects for audio.

 

[Lawrenzini]

Not forgetting that the length of the cable is a massive consideration. In cable runs of less than a couple of meters virtually anything will do the job. Also by increasing the diameter of the cable you can make up for most problems.

Furthermore HDMI is a digital cable, on a run of <10m you're gonna have some fun affecting a digital signal.

 

[jtizzle]

Resistance:
Skin effect:
Capacitance:
Impedance:
Crosstalk:

The principles.

All affect the quality of a sound signal.

All affect the quality of a video signal.

That is all I meant to say.

Please don't split hairs that were never presented for splitting.

I wish I could have seen Johnny Thunders live just once. Sadly, he was just a bit before my time. You are a lucky man, Quint. Your taste in music is beyond reproach.

 

[dvw]

Isn't this the wrong place for a cable discussion?

 

[fuzydice]

Quote:

Originally Posted by dvw /img/forum/go_quote.gif Isn't this the wrong place for a cable discussion?

yep.