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Audio Cables

M

mykel

Weaksauce
Joined
Jul 9, 2004
Messages
76
Where's a good place to get quality cables for SPDIF? Coax, not optical.
I need 5 or 6 feet of it. Cheap is good. I just don't want to give Best Buy or any of them money for a plastic case when all I want is the cable.

Thanks!
 
go to radio shack and snag a good rca cable for $5-10
 
Make sure it is a 75 ohm cable, though.
 
Make one yourself.
Here is how----> http://www.enjoythemusic.com/etmcable.htm
Three things I would do differently then that tutorial.....
I would use solder on RCA connectors.
I would also pick up some Radio Shack #910-1587 cable (this is the same as Belden 1506A) cable and I would add a small mica or ceramic disk . 01uF capacitor between the sheild and the ground ring on the destination side rca jack.

If I was gonna BUY a cable I would buy another one of these.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=14965&item=5718353389&rd=1

Hurry there is only 18 minutes left on that auction. ;)
 
As an eBay Associate, HardForum may earn from qualifying purchases.
dont buy those expensive cables with all those "features." its all hype.
 
although i dont know the signifigance of a 75 ohm cable, used a standard radio shack RCA cable for my coax and it sounds perfect
 
bjornb17 said:
although i dont know the signifigance of a 75 ohm cable, used a standard radio shack RCA cable for my coax and it sounds perfect
Click to expand...
How can you say "it's all hype" if you can't even understand the significance of a 75 ohm impedence? Who are you to judge?
 
From http://www.audioholics.com/techtips/audioprinciples/interconnects/ComponentVideoCables_2.php
2.3 Mismatched Impedance

Mismatched impedance is one of the most common and most frequently experienced sources of signal degradation. This phenomenon occurs when a high frequency bandwidth signal, designed to be matched to a characteristic impedance of 75-ohms, encounters different impedances through its signal path (IE. Transmission Line), usually on the order of 35-ohm or 50-ohm for Home Theater applications. It can occur in long runs of video cables (> 1/10th the wavelength) that do not use true 75-ohm cables, or it can occur from the DVD player or the TV monitor, depending on the nature of their internal impedances. This mismatch can create a bounce back effect or reflection that results in a delay and/or loss of signal level for certain frequencies. Thus for component video cable, transmission line effects of any cable lengths beyond 3 meters (remember 1/10 of 30 meters) must be considered.

When the characteristic impedance changes in a cable, part of the signal (incident wave) is reflected. The reflection coefficient can be calculated as:

image004.gif


Where Vi and Zo are the incident voltage and characteristic impedance of the first media. Vr and Zr represent the reflected voltage and characteristic impedance of the media that caused the reflection.

An open circuit implies that Zr = ∞ or ρ = 1, and a short circuit implies that Z R = 0 or ρ = -1. A perfect reflection coefficient is when Zr = Zo or ρ = 0.

The decibel loss due to reflection is given by:

image005.gif


Power from reflected signals are reflected back to the source (DVD player) so that phase addition and subtraction of the incident and reflected waves create a voltage standing wave pattern on the cable. The ratio of the maximum to minimum voltage is know as Voltage Standing Wave Ratio (VSWR) and can be defined as:

VSWR = Emax/Emin = (Ei+Er)/(Ei-Er)

where:
E max = maximum voltage on the standing wave
E min = minimum voltage on the standing wave
E i = incident voltage wave amplitude
E r = reflected voltage wave amplitude

In the case where the conductor line is properly terminated into its characteristic impedance (75-ohm for component video cables), VSWR = 1 and there is no reflected wave.

The reflection coefficient (r) is defined as E r /E i and in general, it will be a complex number.
Additionally we define: r = (Zi - Zo) / (Zi + Zo)

The refection coefficient (r) , is the absolute value of the magnitude of G .

If the equation for VSWR is solved for the reflection coefficient, it is found that:

Reflection Coefficient = ρ = |r| = (VSWR -1) / (VSWR + 1)

Consequently,

VSWR = (1 + p) / (1-p)

The return loss is related through the following equations:

Return Loss = 10log [Pi/Pr] = -20log [(VSWR -1) / (VSWR + 1)] = -20log ρ

Return loss is a measure in db of the ratio of power in the incident wave to that in the reflected wave, and as defined above, always has a positive value. For example if a load has a return loss of 10 db, then 1/10 of the incident power is reflected. The higher the return loss, the less power is actually lost.

Impedance mismatch can occur when a cable with internal impedance less than 75-ohm is connected to a true 75-ohm load, such as a video line driver in a Projector to DVD player. In this situation, some of the frequencies that make up the signal will be reflected back to the source. Since the source is a 75-ohm impedance, this reflected signal is sent directly back to it creating a delay effect at certain frequencies. This delay, for example, can show up as a ghost in the picture. Multiple ghosts resulting from multiple frequency reflections can look like ringing around the original image. These reflections can also cause partial signal cancellations at various frequencies corresponding to a partial signal loss resulting in a loss of picture detail or color.

Other examples of mismatched impedance include any mismatches between the source's output impedance (DVD player), the cable's characteristic impedance (using audio cables or a poorly made 75-ohm cable), and the load's input impedance (the TV monitor). One possible scenario is if damage to a component video cable from crushing or kinking has occurred, or if the connectors are improperly installed, the internal impedance of the cable is changed resulting in reflection and power or signal loss.
Click to expand...
 
xonik said:
Who are you to judge?
Click to expand...
Do you think that with the speakers he has listed in his sig he would ever notice the subtle improvement a decent coax cable would offer? :p

I realize that is not what you asked.... and it is not meant as a cheap shot twards bob's system.... it is simply a dumb question. :D
 
I plan on upgrading the my speaker to some really nasty ones. 200$+/sat

Sorry for not mentioning that! :D
 
you'll know pretty quickly with a digital signal if the cable is any good. Higher quality cables are more important (to a point) with analog signals. Less critical for digital... assuming the whole signal gets where its going.
 
why do all thoes examples of 75 ohm cables relate to video signals?

Also, i said its all hype becuase i have paid $40+!!!! for monster cables and realized they didnt sound any better than my $10 radio shack cables. Unless you have those fabled "golden-ear" (aka, ears that let you hear subtle differences, even those caused by the power of suggestions).

If you look into help FAQs about which types of cables to get, you'll realized that most advertising for cables is mostly hype, and hardly any science is there to back it up.
 
bjornb17 said:
why do all thoes examples of 75 ohm cables relate to video signals?
Click to expand...
because for an analog video signal the type of cable is much more important.
 
bjornb17 said:
why do all thoes examples of 75 ohm cables relate to video signals?
Click to expand...
Because it's just as applicable in the audio field. Frequency reflection cause signal loss, and do you think that signal loss would affect the accuracy of the digital stream? I don't need to answer that.
 
I'm partial to the Blue Jeans Cables. They have all of the high quality parts, but less markup than the competitors. I like that they are upfront about the parts they use, so that you can make your own comparisons.
 
xonik said:
Because it's just as applicable in the audio field. Frequency reflection cause signal loss, and do you think that signal loss would affect the accuracy of the digital stream? I don't need to answer that.
Click to expand...
It can very easily affect it, but with a digital signal, loss of signal quality is going to be very easy to detect while it may be more subtle with analog.
 
Consider that the thread starter is requesting a cable for digital transmissions, do you not find that especially pertinent?
 
Cable arguments are about as pointless as political arguments. Blue Jeans cables have been mentioned three times in this thread, make my post number four. I bought just about every cable in my house from them and haven't had any issues with failure or quality.
 
xonik said:
Consider that the thread starter is requesting a cable for digital transmissions, do you not find that especially pertinent?
Click to expand...
and the fact of the matter is you're less likely to have problems with mismatched cables for a digital transmission than you are with an analog transmission. Having done it countless times myself when in a pinch, the cheapest video cable in the world almost always works fine for digital audio.
 
I'm going to throw my hat in with the "buy the cheap cable" crowd. If you were talking about analog component video, yes, you've got a reason to buy good cables. But for digital audio... Well, if you're getting a screwed up digital signal, you'd know it. Think of clicks and pops in mp3's from scratched CD's--that's what lousy digital data sounds like. And even if you find that the $4 cable doesn't cut it for you, you've lost all of $4. That's about equivalent to the sales tax on some of the "higher end" cables that you find at BB. Just because people sell $50 1 meter SPDIF cables, it doesn't mean that they function ten times better than a $5 cable. It only means that there are people in the world who will pay that much for a cable... Audio is a very subjective thing, and the psychology involved with paying exorbitant amounts for audio gear only adds to the lack of objectivity...
 
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