The cost of cabling

I went shopping for cables to connect the digital I/O on my sampler to my new soundcard. So I need two SPDIF rca cables and a BNC wordclock cable. The best prices I could find was $30.99 for the SPDIF and $6.98 for the BNC. A total of $68.96! OUCH!

Then I decided to search the web.
http://www.cablesnmor.com/index.asp

check it out. SPDIF and BNC are both 75 ohm. BNC cables $4, BNC to RCA adapters $2. The whole enchilada $20. Digital I/Os AND food in my belly - priceless!
 
Somnium7 said:
I went shopping for cables to connect the digital I/O on my sampler to my new soundcard. So I need two SPDIF rca cables and a BNC wordclock cable. The best prices I could find was $30.99 for the SPDIF and $6.98 for the BNC. A total of $68.96! OUCH!

Then I decided to search the web.
http://www.cablesnmor.com/index.asp

check it out. SPDIF and BNC are both 75 ohm. BNC cables $4, BNC to RCA adapters $2. The whole enchilada $20. Digital I/Os AND food in my belly - priceless!
Can't you use just any old RCA cable for SPDIF or does it have to be something special? I mean, I have a good quality shielded video cable on mine but could I have used anything lesser?
 
RawDepth said:
Can't you use just any old RCA cable for SPDIF or does it have to be something special? I mean, I have a good quality shielded video cable on mine but could I have used anything lesser?

Impedance mismatch with digital signals can result in a rounding off of the square waves (bits) being transmitted. If the rounding becomes severe the reciever will have trouble detecting the edges of the waves and start losing data. Data loss can manifest itself as clicks, gaps or no sound at all.

In my setup I am only needing the signal to travel 10 feet, so I could get lucky with a normal RCA cable but then there is the shielding factor. A proper cable for digital data is constructed with good shielding and this is for a reason. The bits in the transmission are sharp cornered square waves. For each sharp corner in a waveform there is an almost unlimited number of harmonics. In a cable with inadequate shielding there will be a large amount of RFI due to these harmonics. If this RFI is inducted into a nearby audio line it can play havoc on your sound quality. Any device that will amplify the audio in the affected cable will start to amplify the subharmonics in the interference and these can be audible.

This is a very complex subject and I'm not good at explaining it at 3am. there is alot of good technical info on the web about this if you are inclined to get some cold hard facts.
 
Somnium7 said:
Impedance mismatch with digital signals can result in a rounding off of the square waves (bits) being transmitted. If the rounding becomes severe the reciever will have trouble detecting the edges of the waves and start losing data. Data loss can manifest itself as clicks, gaps or no sound at all.

In my setup I am only needing the signal to travel 10 feet, so I could get lucky with a normal RCA cable but then there is the shielding factor. A proper cable for digital data is constructed with good shielding and this is for a reason. The bits in the transmission are sharp cornered square waves. For each sharp corner in a waveform there is an almost unlimited number of harmonics. In a cable with inadequate shielding there will be a large amount of RFI due to these harmonics. If this RFI is inducted into a nearby audio line it can play havoc on your sound quality. Any device that will amplify the audio in the affected cable will start to amplify the subharmonics in the interference and these can be audible.

This is a very complex subject and I'm not good at explaining it at 3am. there is alot of good technical info on the web about this if you are inclined to get some cold hard facts.
This is so wrong... in so many ways. Just buy yourself a couple of quality 75 ohm video cables and then take yourself (and a friend) out to a nice dinner with the change
 
MOFO Pro said:
This is so wrong... in so many ways. Just buy yourself a couple of quality 75 ohm video cables and then take yourself (and a friend) out to a nice dinner with the change

Please enlighten me then.
Some restaurant suggestions would be nice too...
 
Somnium7 said:
Please enlighten me then.
Some restaurant suggestions would be nice too...
Well there's Denny's... And to each of your points... alone and in a different context... I would not dissagree... But your response was specifically targeted at a question about the quality needed for SPDIF cable. Most of the harmonic and RF interferences that you mention are real issues in a anolog environment... and though some of the same interaction occur within the digital domain, there effects are no where near distructive.

A quality 75 ohm cable is a a quality 75 ohm cable... they just increase in price 10 fold when you print SPDIF on them.

I don't think I've ever had an issue with RFI effected a digiital signal... no mater how strong...

Just didn't want this guy spending $100 in cables when $10 would do... There's a chance I could hook up any day... but I don't put on a condom every time I leave the house. You can be too careful
 
Square waves??? What the hell are you guys talking about?

Digital music data is a series of numeric values, not waves. :confused: :confused:
 
RawDepth said:
Square waves??? What the hell are you guys talking about?

Digital music data is a series of numeric values, not waves. :confused: :confused:

The ones and zeroes go through the cable as a square wave voltage with two values, high and low. It's not a tube with zeroes and ones rolling through it. :)

Ones and zeroes, in reality, only exist on your monitor. Everything else is a voltage, analog or digital.
 
dementedchord said:
the rounding of the square wave is really a function of capacitence not termination/impedence...

This is certainly the case with audio signals. A digital audio signal is transmitted at radio frequencys where capacitance isn't as big of a problem. With RF there are other factors such as dielectric absorbtion and reflection. I remember from troubleshooting the avionics in F/A 18 Superhornets that reflection was the real killer of data integrity and usually caused by impedance mismatch. In a video signal reflection results in ghosts on the TV screen. When reflection occurs it basically creates a standing wave within the line which affects the signal by creating ringing, stair-stepping, overshoot and undershoot. On an oscilloscope you can see much worse stuff than just rounding of the waveform when there is reflection.

As far as cables go it is fine to use good video cables because they are designed for impedance matched signals and have the shielding to prevent gross levels of RFI. Like I mentioned above you can even get away with cheap BNC cables and save even more $$$.

I'm off to Dennys now for my meat lovers skillet. :p
 
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