Sub cable unidirectional??? Complete beginner, be gentle.

[runswithscisors]

I just got my Monster Cable 24' sub cable today. Just unpacked it and one end has a little band on it with arrows pointing towards the RCA connector on the end.

Did I miss a memo? Are they making RCA cables unidirectional now? I unscrewed the covers on the soldered on connectors and couldn't find anything but normal soldered connections.

 

[Nestor]

I just got my Monster Cable 24' sub cable today. Just unpacked it and one end has a little band on it with arrows pointing towards the RCA connector on the end.

Did I miss a memo? Are they making RCA cables unidirectional now? I unscrewed the covers on the soldered on connectors and couldn't find anything but normal soldered connections.

Without pictures, I have no idea why they would have such markings. The cable makes no difference which end is plugged in.

Can you return it?

If you research "Monster" on this site, you'll see why.

 

[Rickster71]

I just got my Monster Cable 24' sub cable today. Just unpacked it and one end has a little band on it with arrows pointing towards the RCA connector on the end.

Did I miss a memo? Are they making RCA cables unidirectional now? I unscrewed the covers on the soldered on connectors and couldn't find anything but normal soldered connections.

It's to help eliminate some ground loops / hum. The shield isn't connected at both ends, only at the source end.
The arrows should point toward your sub.

 

[runswithscisors]

It's to help eliminate some ground loops / hum. The shield isn't connected at both ends, only at the source end.
The arrows should point toward your sub.

I was off searching Monster, to no avail other than Monster Cable being a(nother) dirty company. But, $15 for a 24' sub cable shipped, I don't care what name it has on it.

Thanks for the reply, that does make sense. I just unscrewed the end covers again, low and behold, that's exactly what is going on.

 

[jonnythan]

Monster cable is usually very overpriced, but the cables themselves are fine. If you're paying reasonable prices for them then don't worry about it.

 

[TLS Guy]

I was off searching Monster, to no avail other than Monster Cable being a(nother) dirty company. But, $15 for a 24' sub cable shipped, I don't care what name it has on it.

Thanks for the reply, that does make sense. I just unscrewed the end covers again, low and behold, that's exactly what is going on.

Yes, and those cables are a really bad idea. Send them back.

Lifting, or floating the ground in an unbalanced circuit can not be recommended.

It makes the cable much more likely to pick up RF interference, say from dimmer switches.

Worse, all signals have to flow as a circuit, and lifting the ground makes the signal follow a circuitous root all the way though your house wiring, usually resulting in serious attenuation of the signal.

And By the way this approach usually increases noise not reduce it.

Here is what others say: -

This is Kurts response (http://forums.audioholics.com/forums/737906-post36.html) (Owner of Blue Jeans Cable) to this potential variety of cable:

I wouldn't be so quick to assume it's a floated shield. I have seen a lot of different rationales offered for "directionality," none of which make a lot of sense, and without an explanation from the vendor as to what the arrows are purported to mean, or how the cable is internally wired, it's anybody's guess.

Telescoping a shield like this, incidentally, does not really work in unbalanced circuits. When it's done, the two RCA grounds are ordinarily connected by an inner conductor (that is, "balanced" type cable has been used to connect unbalanced gear), because if the cable doesn't contain a signal return path, the return can wind up being quite indirect, which often will result in a lot of noise as well as attenuation of the signal. It does work in balanced gear sometimes (not to reduce induced noise, but to eliminate ground loops), but that's because in balanced circuits there are two signal conductors and both are isolated from ground and have equal impedance to ground but opposite polarity. Anyhow: because there is a conductor in the cable joining the RCA grounds, noise on the shield CANNOT be isolated from either side--it just has a slightly more indirect, but still highly conductive, path to the one side than the other.

Telescoping a shield to reduce induced noise would be an unusual solution and will, in most circumstances, be ineffective. Shield effectiveness is dependent, among other things, on the shield being well-grounded, and removing the ground at one end of the shield will compromise shield effectiveness. In an unbalanced circuit you WANT the noise to shunt to ground, and anything which reduces shield effectiveness will result in more noise reaching the signal side of the circuit.

I have seen a lot of strange rationales given for directional arrows on various cable products. Some people think that copper "sounds" different when hooked up in the direction the wire was drawn, for example (which of course ignores the fact that the signal is alternating current and flows as much in one direction as the other). Some manufacturers put little RC networks into one end of the cable. The floated shield is one possibility, but certainly not the only one, and absent an explanation from Monster I wouldn't assume that that's what's been done here.

Kurt
Blue Jeans Cable

This issue is also addressed in An AES paper on this subject. It clarifies signal ground and chassis ground.

Signal and chassis ground should be tied together in every unit.

So what if you have a sub with a two pin connector. Chassis and signal ground have to be tied in a unit like that to work. So both signal and chassis float.

So if you use a cable like you describe, the signal has little or no way back to make a circuit, resulting in no signal or severe attenuation.

A small snippet from a long AES paper; -

Unbalanced units connect successive signal grounds together directly through each interconnecting cable -- the sleeve of each RCA cable. This, and the fact that the chassis is generally used as a signal ground conductor, keeps the signal ground impedance of unbalanced systems very low. Many may agree that unbalanced systems are helped by the fact that the chassis are normally not earth grounded. This allows an entire unbalanced system to float with respect to earth ground. This eliminates the potential for multiple return paths for the audio grounding system, since there is not a second path (ground loop) through the earth ground conductor. Low signal ground impedance between units is essential for acceptable operation of all non-transformer-isolated systems, balanced and unbalanced.

So I hope you get the picture, that the cable you have is a very bad idea indeed.

 

[Adam]

I have one of those Monster sub cables from when I bought my first sub in the 90s. Worked great. As Jonnythan said, it was overpriced (in my case) - but it works. I bought a new cable when I bought my SVS in 2007, and it works great, too.

Like you said, run, it's a decent price for a sub cable. It'll be more hassle than it's worth to send it back and get a "better value." Plug it in and enjoy. If you start getting a bunch of hum, then just remember what TLS said when you're trying to troubleshoot it.

 

[markw]

Monster is overpriced but they usually make a decent product. If he cable works and doesn't introduct any noise (and I doubt it does), just use it and forget about all the scare tactics you occasionally read about here from some. Some people just love to spread audio nervosa.

 

[TLS Guy]

Monster is overpriced but they usually make a decent product. If he cable works and doesn't introduct any noise (and I doubt it does), just use it and forget about all the scare tactics you occasionally read about here from some. Some people just love to spread audio nervosa.

Just think about this for a minute.

All electric circuits are just that. An equal number of electrons must flow from the source and through the load back to the source. That is why it is called a circuit.

So in a normal cable the electron flow in the live end equals the flow in the screen. It has too, there is no other solution.

So now lets take an unbalanced cable with a lifted ground to a sub.

Case I: - Three pin AC lead on sub and receiver, both sub and receiver on same circuit. This will likely work OK as the return path will be about equivalent to the grounded cable.

Case II: - Three pin plug on both receiver and sub, but sub on a different circuit. The return path now all the way to where ever the grounds common. Likely not so good.

Case III: - Both receiver and sub have two pin AC plugs. Now the return is through the neutrals of the receptacles, to wherever the neutrals are common. If same circuit not good practice but may get away with it. Different circuits bad.

Case IV: - Either the receiver has a two pin AC plug and the receiver a three pin plug, or vice verse. Now the return is all the way to the panel were the neutrals and grounds are joined. Very bad.

So anyone who thinks lifting a ground on an unbalanced circuit is a good idea, does not understand electric circuits very well.

Lifting the screen on a balanced circuit is a totally different situation, since the signal return path is not the cable screen.

 

[Adam]

Whew - I sure was lucky, playing with fire all those years.

 

[markw]

Whew - I sure was lucky, playing with fire all those years.

Me too. I guess ignorance truly is bliss. I guess I'm too stoopid to know that I wasn't heering gud sound.

The fact of the matter is that in most cases, a lifted ground doesn't make a bit of a difference. In a very few cases, it can, and when it does, it can make an improvement.

The thing to this hobby is to sweat what matters, and to know what matters and what really doesn't. ...or, it it ain't broke, don't fix it.

 

[TLS Guy]

Whew - I sure was lucky, playing with fire all those years.

You would only be playing with fire unless there was a live neutral reversal at an outlet.

However codes in most jurisdictions allow daisy chaining of neutrals. This is now being looked at, and not allowed in a few jurisdictions. The vast majority of American homes have daisy chained neutrals. Now however, there is increasing attention being paid to neutral gouging, especially from fluorescent light bulbs, and switching power supplies in computers and subs etc. These and other circuits load neutrals in ways that did not commonly happen years ago, when the codes were written.

So it is possible for significant voltage to appear on neutrals.

With the disconnected ground like we are talking about, it would be possible for a voltage, and it would only take around five volts, to fry a receiver or sub. So that is likely are not often thought about cause of equipment failure.

That for me is another reason to avoid the cables under discussion if there is any possibility of neutrals being involved in the return path.

 

[Adam]

You would only be playing with fire unless there was a live neutral reversal at an outlet.

I didn't mean that literally, Mark.

I respect the knowledge and appreciate the information/guidance. I do think that the cable will likely work fine, though, and that people can reference your remarks if they do experience issues.

I'm not recommending that people go out and buy unidirectional RCA cables, but I also don't recommend replacing any existing ones unless there's a problem.

 

[Rickster71]

Now however, there is increasing attention being paid to neutral gouging, especially from fluorescent light bulbs, and switching power supplies in computers and subs etc. These and other circuits load neutrals in ways that did not commonly happen years ago, when the codes were written.

So it is possible for significant voltage to appear on neutrals.

With the disconnected ground like we are talking about, it would be possible for a voltage, and it would only take around five volts, to fry a receiver or sub. So that is likely are not often thought about cause of equipment failure.

That for me is another reason to avoid the cables under discussion if there is any possibility of neutrals being involved in the return path.

I used to use this cable in non-linear loaded environments. KAF-TECH: Product Specs: Super Neutral Cable®

 

[Alex2507]

... non-linear loaded environments ...

Is he allowed to use words I don't understand ?!?

 

[Rickster71]

Is he allowed to use words I don't understand ?!?

Jobs with lots of computers and electronic ballasts on the lights.

 

[Adam]

Is he allowed to use words I don't understand ?!?

If he wasn't, he'd never get to post.

 

[TLS Guy]

I didn't mean that literally, Mark.

I respect the knowledge and appreciate the information/guidance. I do think that the cable will likely work fine, though, and that people can reference your remarks if they do experience issues.

I'm not recommending that people go out and buy unidirectional RCA cables, but I also don't recommend replacing any existing ones unless there's a problem.

I would definitely change out one of those cables, if it was one of the scenarios I mentioned that would involve a return through household neutral wiring. I would absolutely do it to reduce the chance of equipment failure due to a voltage appearing on neutral from gouging.

 

[runswithscisors]

Well, I plugged in my cable to the sub, plugged everything in, nothing. I turned the system on, nothing. I turned the sub volume up to the 12:00 position, nothing. I put my hand on top of the sub, nothing. I put my hand on top of the receiver, nothing. I started the BR disc, bass came out of the sub, nothing else.

I think if this were a serious issue Monster would have a class action on their hands, and from the looks of things their legal department is too busy chasing sellers on Craigslist to be tied up in that sort of thing.

Besides, its just a temp cable till I upgrade from my Onkyo HTIB sub to my new HSU, then I'll use the cable to do the sub crawl and run some RG6 in the wall.

 

[runswithscisors]

I will add this about the cables construction, it has dual core wires, connecting the center pins together and the outer contactors together, but the shielding is only soldered to the outer contactor, along with the second core wire, on the receiver end of the cable. I would snap some pics but I'm not taking my system back apart, I'm too busy enjoying it.