AVS Forum banner

Status
Not open for further replies.
1 - 10 of 10 Posts

·
Registered
Joined
·
190 Posts
Discussion Starter · #1 ·
Can one use a 75 ohm video cable for analog audio, or will this affect the sound in a detrimental way? I know that one can use a video cable as a digital coax, but I wasn't sure if it would be okay for analog audio.


I'm only asking because my brother is running a video cable to his powered sub (none of this other cables were long enough), and it seemed like it might be problematic.


Thanks!
 

·
Registered
Joined
·
22,160 Posts
A video cable to a powered sub should be fine. The sub line level is 75Ohm, same as video.


Usually though (unless it's a high quality), those video cables (yellow ends right?) are pretty shoddy quality.


You could always make a sub cable using RG6 coax and either install RCA plugs on the ends or purchase F to RCA converter plugs.
 

·
Registered
Joined
·
190 Posts
Discussion Starter · #3 ·
R -- Thanks for the helpful response. The video cable is actually one of the R. Shack "gold" video cables, so it's probably not too bad, as inexpensive composite cables go. Plus, the signal is coming out of a $199 JVC Pro-Logic receiver to a $79 KLH subwoofer, so he's got bigger problems to solve!!!
 

·
Registered
Joined
·
48 Posts
As a side note: I recently tested the capacitance of the standard Red, White, Yellow RCA type cable that comes with my satellite system and the capacitance was; 950pF (Red), 941pF (White), and 150pF (Yellow) respectively. That is just one area video and audio cables shows some difference.
 

·
Registered
Joined
·
513 Posts
Quote:
Originally posted by Ratman
A video cable to a powered sub should be fine. The sub line level is 75Ohm, same as video.
I thought that 75 ohms was only needed for high frequency video signals. I'm also planning on running video cables for my subs and found this thread in a search for the following question:


My video and audio cables will both be made out of Canare L-5CFB RG6 coax with Canare 75 ohm RCA connectors. I'm sure that the RCA to RCA wall jack that I want to use is not a true 75 ohms nor is the 90 degree RCA to RCA adapters or the Y adapters. Does this matter or should I make sure I have a solid balanced 75 ohm run between all cabling and connectors in the audio run?


I've always heard that very few audio cables are actually 75 ohms. Is this because they just don't need to be or is that just the difference between cheap audio cables and the expensive ones? If not what is the difference?


Where can I find 75 ohm Y adapters if I need them or 90 degree adapters?


I was hoping to order all my cabling today. Hopefully one of you knowledgeable audiophiles can help me out fast. Thanks


Brent
 

·
Registered
Joined
·
7,655 Posts
You can have the Y adapters made several places. www.cobaltcables.com has them premade. www.catcables.com will make them too.


Just reading your post, I would SERIOUSLY rethink your plan. You have a TON of connectors in the path. Each one is a place for noise, dirt, corrosion, oxidation, resistance to enter your system. Keep the number of connections to a minimum. Why the 90 degree adapter? I would just have a long Y cable made up that you can plug directly into the wall plate. That way, you only have one set of extra connections.


The Canare cable and RCAs are fine. You CAN get true 75 ohm feedthrough RCA to RCA barrels for wall plates from www.markertek.com. Make sure to get the RCAP series RCA connectors for the video cables. For the audio cables, those will work too but you can get by with the F10s if you want. The only audio cable I would worry about a true 75 ohm connection is the SPDIF cable.
 

·
Registered
Joined
·
513 Posts
bpape,


Thanks for your response. Trust me, I know that having the minimum amount of connections in the system is best and I've tried to plan it out that way.


The 90 degree adapter is for the room side of the wall plate and only necessary because a book case will probably be placed in front of the wall plate. I want the book case as close to the wall as possible but might forgo the 90 degree adapter if everything looks fine without it. I only need the Y connector right at the output of the stereo to run two different cables to two different subs in two different opposite locations. That's it. I don't think it's that unreasonable. If extra connections were all that terrible nobody would use wall plates and instead just have a cable poking out through a hole in the wall.


Having a long Y cable made up would totally go against the justification I went through for buying an expensive stripper, crimper and die in order to build all the cables myself.


I'm planning on using the RCAP connectors for everything since I don't think the F10 uses the same Canare die but I will check on that. Markertek is where I'm getting all this stuff but couldn't find Canare RCA jack to RCA jack wall plate barrels, only RCA jack to solder or RCA jack to BNC. I'll ask when I place my order.


Thanks again. I do appreciate your input about the 75 ohm issue.


Brent
 

·
Registered
Joined
·
1,881 Posts
Quote:
Originally posted by felthove
Can one use a 75 ohm video cable for analog audio, or will this affect the sound in a detrimental way? I know that one can use a video cable as a digital coax, but I wasn't sure if it would be okay for analog audio.
Video and digital audio require 75-ohm coax, but characteristic impedance doesn't matter foranalog audio, so any decently made, properly shielded coax (including 75-ohm) will work. If you have a long run of analog cable, it is good to keep the capacitance low.
 

·
Registered
Joined
·
1,881 Posts
Quote:
Originally posted by Ratman
A video cable to a powered sub should be fine. The sub line level is 75Ohm, same as video.
There is no particular impedance associated with line-level subwoofer inputs, though it normally would be 10,000 ohms or more, the same as for any other line-level input. Nothing needs to match that impedance, but the output impedance of the source feeding it should be much lower--less than 1,000 ohms and preferably more like 100. The cable impedance doesn't matter at all.
 

·
Registered
Joined
·
7,655 Posts
Markertek does have wall plate RCA/RCA Barrels.


As far as having cables haning out of the wall, most who are REALLY SERIOUS about it do just that. I certainly do. My only connections are at the preamp and the amp. The only exception is the Y adapter for my dual subs. It just takes a bit of time to MAKE custom wallplates from wood that are split through the holes so they can be placed around the cables in 2 parts and then screwed together to the box.


You can still make the long y cable yourself. You just need to get some shielding to put over the connection at the y and be real good with a soldering iron.
 
1 - 10 of 10 Posts
Status
Not open for further replies.
Top