where to place down firing sub

[InVeNtOr]

arky, since you own canare cables, how do the monoprice compare to them? what is the honest opinion? it seems to me you went with it because it was $12, which i would like to add, it is hard to beat that price. especally when someone else is asking for around $100. every dollar helps and counts.

[Arky]

I bought the sub cable from mono because it was cheap & figured I couldn't tell the difference if there is any. All of my other cables came from bluejeans.

Now superbowl week I helped one of my lawyer buds go HD sat in his office lounge. We have 3 LCD tv's so I needed 3 HDMI 9' cables & 2nd day air shipping so I went cheap as I could find to get up & running for the game. Total was $39 from monoprice. I ain't paying $150 for a cable. Honestly, the build looks not as good as my bluejeans but they work & the picture is really good. Maybe they won't last, IDK.

[westcott]

arky, since you own canare cables, how do the monoprice compare to them? what is the honest opinion? it seems to me you went with it because it was $12, which i would like to add, it is hard to beat that price. especally when someone else is asking for around $100. every dollar helps and counts.

I do not take chances with subwoofer cable. Most of the time, you are just fine but every once in a while, ground loops rear their ugly head. If you have easy access to your cables and have no problem replaciing it, then you might want to go with a cheaper solution.

[Arky]

Agreed. My application is post construction. I've been lucky to never had any ground or hum issues. Maybe I have good electricity.

[mas]

If you are having cables made, or if you make them yourself, this (a ground loop) is easily avoided. Simply specify that the shield on the subwoofer end be lifted and the end indicated on the cable.

You now have a 'directional' cable.

[westcott]

If you are having cables made, or if you make them yourself, this (a ground loop) is easily avoided. Simply specify that the shield on the subwoofer end be lifted and the end indicated on the cable.

You now have a directional cable.

This is a not a good idea IMO, ground loops should be dealt with using an isolation transformer, or simply making sure that all the equipment is plugged into the same electrical circuit. Disconnecing one end of the shield forces the cable length to act as the ground, like an antenna, which could have some undesirable results.

The best defense is a dense and highly-conductive braid shield. I recommended subwoofer interconnect cables have not one, but two, dense braid shields. BJs testing testing has found this to be the best shield configuration, outperforming conventional single-braid, braid-and-foil, and unbalanced twisted-pair cables when it comes to hum rejection.

[mas]

It is ironic that this month in Live Sound, even Bill Whitlock recommends just what I stated.

Disconnecting the shield on the 'outbound' end prevents the cable for acting as an alternative ground path. This is not a new technique. It works great. And it is also particularly effective a shield against RF and EMI.

And an isolation transformer is fine for a 75 ohm system where the impedance is known and standardized. But it is not always a practical solution.

RG-6 cable featuring double foil, double braid is more effective than foil and a drain wire with regards to RF and EMI ingress, but provides no protection against ground loops where the shield is simply a conductor.

RF/EMI and ground loops are two separate issues, both of which can be addressed just fine using RG6 with double foil double braid with the shield lifted on the outbound end. This technique will work with 'any' interconnect. And if you are dealing with a system with a characteristic 75 ohm impedance such as a video distribution system (cable, satellite, etc.) and in line isolation transformer which effectively does the same thing, may be employed.

[westcott]

It is ironic that this month in Live Sound, even Bill Whitlock recommends just what I stated.

Disconnecting the shield on the 'outbound' end prevents the cable for acting as an alternative ground path. This is not a new technique. It works great. And it is also particularly effective a shield against RF and EMI.

And an isolation transformer is fine for a 75 ohm system where the impedance is known and standardized. But it is not always a practical solution.

RG-6 cable featuring double foil, double braid is more effective than foil and a drain wire with regards to RF and EMI ingress, but provides no protection against ground loops where the shield is simply a conductor.

RF/EMI and ground loops are two separate issues, both of which can be addressed just fine using RG6 with double foil double braid with the shield lifted on the outbound end. This technique will work with 'any' interconnect. And if you are dealing with a system with a characteristic 75 ohm impedance such as a video distribution system (cable, satellite, etc.) and in line isolation transformer which effectively does the same thing, may be employed.

On an unbalanced connection, which is what ordinarily is being run to a typical subwoofer, if one breaks the shield at one end, the problem that results is that there's no signal return path in the interconnect. The signal return path which results will be indirect or even practically nonexistent, and there's liable to be a lot of noise associated with it.

If this were a balanced connection, then it's a different story, and I'd agree with the advice given. That's because in a balanced connection, made with a balanced-type interconnect, there is a separate signal return conductor, and the signal return is not dependent on the cable shield. Breaking the shield at one end may well resolve a ground-loop problem, and is a common way of doing so. Most people here are home theater consumers, most of whom are running subs which are fed through an unbalanced input, and my previous advice would apply.

[mas]

Neither RG6 nor speaker cable is a balanced connection. Thus a discussion of balanced CMNR is not really appropriate for unbalanced speaker cables.

And in an unbalanced cable, there is (or should be!) no signal 'return'. Lifting a ground is only appropriate in an unbalanced cable. And lifting the ground/shield on an unbalanced connection simply prevents an an additional ground path, thus eliminating a source of ground loops, while providing a grounded source of RF and EMI shielding provided the ground is maintained in a star configuration using the pre-amp as a reference point. Thus lifting the ground on the device end opposite the pre-amp is quite effective. Unfortunately, the 'signal return path' you refer to is exactly what a ground loop is.

Likewise, a balanced connection must always be grounded at the driver and never only at the receiver.

So we need to understand that we do not simply lift a ground in a balanced connection. It is important to understand the differences and to distinguish between the two 'types'. Balanced connections traditionally are subject to different issues, often referred to as the 'pin 1' conundrum and SCIN (shield current induced noise).

To that end I will post a current on fixing balanced interconnect issues article by Bill Whitlock, who along with Neil Muncy, are the industry's authorities all things regarding 'shielding, grounding, interconnects, RF and EMI'.

...Hope this helps.

Concat.AQuestionOfBalance.pdf

[westcott]

Neither RG6 nor speaker cable is a balanced connection. Thus a discussion of balanced CMNR is not really appropriate for unbalanced speaker cables.

And in an unbalanced cable, there is (or should be!) no signal 'return'. Lifting a ground is only appropriate in an unbalanced cable. And lifting the ground/shield on an unbalanced connection simply prevents an an additional ground path, thus eliminating a source of ground loops, while providing a grounded source of RF and EMI shielding provided the ground is maintained in a star configuration using the pre-amp as a reference point. Thus lifting the ground on the device end opposite the pre-amp is quite effective. Unfortunately, the 'signal return path' you refer to is exactly what a ground loop is.

Likewise, a balanced connection must always be grounded at the driver and never only at the receiver.

So we need to understand that we do not simply lift a ground in a balanced connection. It is important to understand the differences and to distinguish between the two 'types'. Balanced connections traditionally are subject to different issues, often referred to as the 'pin 1' conundrum and SCIN (shield current induced noise).

To that end I will post a current on fixing balanced interconnect issues article by Bill Whitlock, who along with Neil Muncy, are the industry's authorities all things regarding 'shielding, grounding, interconnects, RF and EMI'.

...Hope this helps.

In any circuit that carries information, there always is a signal return path. The difference between unbalanced and balanced connections is that the signal return path in an unbalanced connection is also the ground, while in a balanced connection the two signal conductors operate mutually as signal and signal return, and have (ideally, at least) the same impedance to ground. One can't really send electrical signals without a return path--because the receiving device needs to be able to sense the voltage on its input, and voltage is a relative phenomenon which exists only as measured against some reference--the voltage being measured, on an unbalanced input, is the voltage between the signal-side and the ground-side of the circuit. Now, it is often possible to still get a signal when breaking the ground path through the cable--but that's because there are other return paths available. If there were no return path, there would be no signal.

It seems to me that there is some confusion between what constitutes a balanced and what constitutes an unbalanced connection. I certainly would concur that Bill Whitlock is a very credible authority, and I doubt I would disagree with anything he has to say on the subject; but it is important to be sure that one doesn't generalize from his remarks concerning balanced circuits and assume that the same principles will necessarily apply to unbalanced circuits.

[lo123]

I have some Blue Jeans cables for my sub from my Denon receiver to the wall plate, then from the other end of my room from the wall plate to the sub. They were reasonably priced, very nice quality and they shipped as they promised on schedule. Very pleased.

But between the wall plates (in wall, under the floor, back up to second wall plate) I just ran RG-6 from a roll I have from wiring my house for video. Used RCA connectors on the outside of the wall plates for the Blue Jean cables, but used F-connectors on the inside of the wall plates. Terminated my RG-6 coax with crimp F-connectors from Radio Shack (bought the satelite version, beefier for some reason).

While I can't say this is optimum it was inexpensive since I already had a very large roll of RG-6 with much left over coax to work with. If you try that route and find a location you like then you could get the Blue Jeans Belden cable with the Canare connectors once you know your final length.

I bought the RCA connector cables from Blue Jeans plus a 24 foot run to cover my in-wall run. Then my wife put the kabosh on location of my SVS PC-Ultra and you know where it is now - approx 36 cable feet away from the Denon, on the rear wall and behind the recliner. Well, at least I have a sub and can dream of a better setup down the road!

Lesson learned: Play with RG-6 if you have some at bulk pricing. If you want to upgrade later replace it with the Belden from Blue Jeans with the Canare connectors. It is very nice cable. Might sound better, not sure I could hear the difference but maybe someone with a better ear could! Meanwhile, I have a nice 24 foot length of Belden with RCA connectors to play with locations of my sub when the wife is not home, and the SVS rolls quite easily to temporary locations........

[germerikan]

Concerning the placement of the sub I was wondering if anyone else has heard of this method, I found it in a handbook for a pre-amp

Place the sub at your listening position, walk around the room and find out exactly where you are hearing it the best. There is where you should place the sub. It seems to me this would be the fastest method as to finding out where it should go.

[westcott]

Concerning the placement of the sub I was wondering if anyone else has heard of this method, I found it in a handbook for a pre-amp

Place the sub at your listening position, walk around the room and find out exactly where you are hearing it the best. There is where you should place the sub. It seems to me this would be the fastest method as to finding out where it should go.

I think Audioholics calls it the "bass crawl" and it is how I set up my sub, keeping in mind other subwoofer placement principles.

[germerikan]

I think Audioholics calls it the "bass crawl" and it is how I set up my sub, keeping in mind other subwoofer placement principles.

Were there large differences in the different areas of the room, say almost inaudiable to wow, or would you have to listen very closely??

[InVeNtOr]

germerikan, when you do the bass crawl you have the spl meter with you. where ever the meter reads the highest, that is where you place it. usually it's in a corner or near one.

[germerikan]

Since I don't have a SPL meter (yet) I did it by ear and picked the place where it sounded best but actually did not hear a difference that was worlds apart, just wanted to hear your oppinion. I disconnected the mains and just had bass heavy music running. Would using a SPL be more accurate? If so I'll have to get one soon, dont think they cost that much.

[westcott]

I think Audioholics calls it the "bass crawl" and it is how I set up my sub, keeping in mind other subwoofer placement principles.

Were there large differences in the different areas of the room, say almost inaudiable to wow, or would you have to listen very closely??

Huge differences. The closer you get to a wall or a corner, really changes the sound. Standing close to the center of the room will give another sound. An SPL meter will help you tell the differeneces if you find your ear is less tuned to such changes, but once you find a few positions in the room that sounds good and you consider possibilities, you will still have to move the sub to those positions and listen in the primary listening position. Once you have it close, start some calibration testing (I use what came with my Digital Video Essentials DVD, but I am sure there are other solutions) and see how the frequency response is affected. The flatter, the better. This takes some time to do properly. Do not be afraid to experiment. Every room and its furnishings are different. I started with 10Hz frequency steps to 80Hz and then 5Hz steps as I was more comfortable with its placement. As you get closer to 80Hz, pay more attention as this is where your main speakers will hopefully be picking up from. Then complete the rest of the frequency range. Dips are difficult to compensate for so if you have a choice, a hump is more tolerable, as long as its not outrageous. Remember, in a home theater there will be more than one listener, so after you are happy with the primary listening position, test other seating positions close by. There are no short cuts and it takes a LOT of time and testing. Equalization can work but it is best to start by placing the sub where it sounds best without it. EQ can be VERY tricky and I consider it a last resort and something that may be more beneficial as you gain experience.

Just an anecdote. Most people have never heard a properly calibrated sound system. It may sound foreign to you. It may even sound flat,bright, or just down right bad. It is not easy to do because everyones tastes are different and that may be more influential than what is considered ideal. But, I suggest you try it first. Be patient. Give it some time to grow on you. Stick with music you are very familiar with, at first. Take LOTS of notes when you make changes. You may start to notice patterns in your notes. Some people are never happy with the set up and are continually making changes and testing. All of this can be helpful but I am sure you will get 95+% there if you have the patience.

[germerikan]

I think Audioholics calls it the "bass crawl" and it is how I set up my sub, keeping in mind other subwoofer placement principles.

Were there large differences in the different areas of the room, say almost inaudiable to wow, or would you have to listen very closely??

Huge differences. The closer you get to a wall or a corner, really changes the sound. Standing close to the center of the room will give another sound. An SPL meter will help you tell the differeneces if you find your ear is less tuned to such changes, but once you find a few positions in the room that sounds good and you consider possibilities, you will still have to move the sub to those positions and listen in the primary listening position. Once you have it close, start some calibration testing (I use what came with my Digital Video Essentials DVD, but I am sure there are other solutions) and see how the frequency response is affected. The flatter, the better. This takes some time to do properly. Do not be afraid to experiment. Every room and its furnishings are different. I started with 10Hz frequency steps to 80Hz and then 5Hz steps as I was more comfortable with its placement. As you get closer to 80Hz, pay more attention as this is where your main speakers will hopefully be picking up from. Then complete the rest of the frequency range. Dips are difficult to compensate for so if you have a choice, a hump is more tolerable, as long as its not outrageous. Remember, in a home theater there will be more than one listener, so after you are happy with the primary listening position, test other seating positions close by. There are no short cuts and it takes a LOT of time and testing. Equalization can work but it is best to start by placing the sub where it sounds best without it. EQ can be VERY tricky and I consider it a last resort and something that may be more beneficial as you gain experience.

Just an anecdote. Most people have never heard a properly calibrated sound system. It may sound foreign to you. It may even sound flat,bright, or just down right bad. It is not easy to do because everyones tastes are different and that may be more influential than what is considered ideal. But, I suggest you try it first. Be patient. Give it some time to grow on you. Stick with music you are very familiar with, at first. Take LOTS of notes when you make changes. You may start to notice patterns in your notes. Some people are never happy with the set up and are continually making changes and testing. All of this can be helpful but I am sure you will get 95+% there if you have the patience.

Thanks.......I think I will redo my "measurements" with a meter just to see what the difference is, it is great to get helpful info.

[mas]

Neither RG6 nor speaker cable is a balanced connection. Thus a discussion of balanced CMNR is not really appropriate for unbalanced speaker cables.

And in an unbalanced cable, there is (or should be!) no signal 'return' via he shield. Lifting a ground is only appropriate in an unbalanced cable. And lifting the ground/shield on an unbalanced connection simply prevents an an additional ground path, thus eliminating a source of ground loops, while providing a grounded source of RF and EMI shielding provided the ground is maintained in a star configuration using the pre-amp as a reference point. Thus lifting the ground on the device end opposite the pre-amp is quite effective. Unfortunately, the 'signal return path' you refer to is exactly what a ground loop is.

Likewise, a balanced connection must always be grounded at the driver and never only at the receiver.

So we need to understand that we do not simply lift a ground in a balanced connection. It is important to understand the differences and to distinguish between the two 'types'. Balanced connections traditionally are subject to different issues, often referred to as the 'pin 1' conundrum and SCIN (shield current induced noise).

To that end I will post a current on fixing balanced interconnect issues article by Bill Whitlock, who along with Neil Muncy, are the industry's authorities all things regarding 'shielding, grounding, interconnects, RF and EMI'.

...Hope this helps.

In any circuit that carries information, there always is a signal return path. The difference between unbalanced and balanced connections is that the signal return path in an unbalanced connection is also the ground, while in a balanced connection the two signal conductors operate mutually as signal and signal return, and have (ideally, at least) the same impedance to ground. One can't really send electrical signals without a return path--because the receiving device needs to be able to sense the voltage on its input, and voltage is a relative phenomenon which exists only as measured against some reference--the voltage being measured, on an unbalanced input, is the voltage between the signal-side and the ground-side of the circuit. Now, it is often possible to still get a signal when breaking the ground path through the cable--but that's because there are other return paths available. If there were no return path, there would be no signal.

It seems to me that there is some confusion between what constitutes a balanced and what constitutes an unbalanced connection. I certainly would concur that Bill Whitlock is a very credible authority, and I doubt I would disagree with anything he has to say on the subject; but it is important to be sure that one doesn't generalize from his remarks concerning balanced circuits and assume that the same principles will necessarily apply to unbalanced circuits.

Haha. This is a radical case of non communication.

I would say no one is confusing balanced with unbalanced cables, but I must restate that to say that I am not confusing the topologies. And the article has a few useful references to UNbalanced connections as well! But I guess on would have to read it and understand it to realize that!

And you are the one over-generalizing about unbalanced connections.

There is more to the world of unbalanced connections than twin-lead zip

cord!

But then you don't have ground loops with twin lead used between an amp and a passive speaker.

The technique stands. You can avoid a ground loop and also retain what RF/EMI protection is afforded in an unbalanced interconnect (the degree may vary depending upon the actual topology of the interconnect - as there are a variety of unbalanced cable topologies, but I guess it also assumes that one knows this. - e.g topologies such as Canare quad or Mogami Neglex 2534 mic cables can and are used for equipment interconnects and maintain the RF/EMI rejection with such a technique - but obviously not twin-lead speaker cable) by lifting the ground on the downstream end relative to the Pre-amp. And this same technique is accomplished in RG6 coax with an inline isolation transformer that effectively lifts/breaks the shield path while providing for an induced connection - thus avoiding a ground loop in that cable topology.

And do I need to also point out that ground loops are a problem normally encountered between two ACTIVE components?

This configuration is exactly what is commonly referred to as a 'directional cable' (NOT to be confused with the nonsense attributed to wire where the electrons magically flow better in one direction than another!). It is definitely not new nor my unique idea! And the technique has been used easily as long as I have dealt with the issue, which is longer than I want to remember!

But if you want to debate and ponder as to why disconnecting one side of the twin-lead used to feed your speaker fails to make your music play louder, by all means, continue. I assumed, perhaps incorrectly, that we were slightly beyond this point.

Oh, and the technique I mentioned even meets with Bill Whitlock's approval as well! Whereas lifting an equipment AC ground with a cheater plug is NOT an approved method! Of course you would have had to be at one of his and Neil Muncie's led SAC seminars on grounding and noise to know that, I guess. But this is a crazy debate. If you don't want to do it, fine with me. I don't have problems with ground loops. And all of my cables also exhibit continuity as well!

[westcott]

Neither RG6 nor speaker cable is a balanced connection. Thus a discussion of balanced CMNR is not really appropriate for unbalanced speaker cables.

And in an unbalanced cable, there is (or should be!) no signal 'return' via he shield. Lifting a ground is only appropriate in an unbalanced cable. And lifting the ground/shield on an unbalanced connection simply prevents an an additional ground path, thus eliminating a source of ground loops, while providing a grounded source of RF and EMI shielding provided the ground is maintained in a star configuration using the pre-amp as a reference point. Thus lifting the ground on the device end opposite the pre-amp is quite effective. Unfortunately, the 'signal return path' you refer to is exactly what a ground loop is.

Likewise, a balanced connection must always be grounded at the driver and never only at the receiver.

So we need to understand that we do not simply lift a ground in a balanced connection. It is important to understand the differences and to distinguish between the two 'types'. Balanced connections traditionally are subject to different issues, often referred to as the 'pin 1' conundrum and SCIN (shield current induced noise).

To that end I will post a current on fixing balanced interconnect issues article by Bill Whitlock, who along with Neil Muncy, are the industry's authorities all things regarding 'shielding, grounding, interconnects, RF and EMI'.

...Hope this helps.

In any circuit that carries information, there always is a signal return path. The difference between unbalanced and balanced connections is that the signal return path in an unbalanced connection is also the ground, while in a balanced connection the two signal conductors operate mutually as signal and signal return, and have (ideally, at least) the same impedance to ground. One can't really send electrical signals without a return path--because the receiving device needs to be able to sense the voltage on its input, and voltage is a relative phenomenon which exists only as measured against some reference--the voltage being measured, on an unbalanced input, is the voltage between the signal-side and the ground-side of the circuit. Now, it is often possible to still get a signal when breaking the ground path through the cable--but that's because there are other return paths available. If there were no return path, there would be no signal.

It seems to me that there is some confusion between what constitutes a balanced and what constitutes an unbalanced connection. I certainly would concur that Bill Whitlock is a very credible authority, and I doubt I would disagree with anything he has to say on the subject; but it is important to be sure that one doesn't generalize from his remarks concerning balanced circuits and assume that the same principles will necessarily apply to unbalanced circuits.

Haha. This is a radical case of non communication.

I would say no one is confusing balanced with unbalanced cables, but I must restate that to say that I am not confusing the topologies. And the article has a few useful references to UNbalanced connections as well! But I guess on would have to read it and understand it to realize that!

And you are the one over-generalizing about unbalanced connections. There is more to the world of unbalanced connections than twin-lead zip cord!

But then you don't have ground loops with twin lead used between an amp and a passive speaker.

The technique stands. You can avoid a ground loop and also retain what RF/EMI protection is afforded in an unbalanced interconnect (the degree may vary depending upon the actual topology of the interconnect - as there are a variety of unbalanced cable topologies, but I guess it also assumes that one knows this. - e.g topologies such as Canare quad or Mogami Neglex 2534 mic cables can and are used for equipment interconnects and maintain the RF/EMI rejection with such a technique - but obviously not twin-lead speaker cable) by lifting the ground on the downstream end relative to the Pre-amp. And this same technique is accomplished in RG6 coax with an inline isolation transformer that effectively lifts/breaks the shield path while providing for an induced connection - thus avoiding a ground loop in that cable topology.

And do I need to also point out that ground loops are a problem normally encountered between two ACTIVE components?

This configuration is exactly what is commonly referred to as a 'directional cable' (NOT to be confused with the nonsense attributed to wire where the electrons magically flow better in one direction than another!). It is definitely not new nor my unique idea! And the technique has been used easily as long as I have dealt with the issue, which is longer than I want to remember!

But if you want to debate and ponder as to why disconnecting one side of the twin-lead used to feed your speaker fails to make your music play louder, by all means, continue. I assumed, perhaps incorrectly, that we were slightly beyond this point.

Oh, and the technique I mentioned even meets with Bill Whitlock's approval as well! Whereas lifting an equipment AC ground with a cheater plug is NOT an approved method! Of course you would have had to be at one of his and Neil Muncie's led SAC seminars on grounding and noise to know that, I guess. But this is a crazy debate. If you don't want to do it, fine with me. I don't have problems with ground loops. And all of my cables also exhibit continuity as well!

First, "speaker cable" has nothing to do with the matter, since we're talking about a line-level interconnect. Nor have I said anything re: common-mode noise rejection, which was referenced in one of the earlier posts. As noted there, common-mode noise rejection is not a consideration in an unbalanced circuit.

So, what we are talking about is an unbalanced connection, and whether one can break a ground loop by disconnecting the shield at one end.

Now, there are multiple ways to run an unbalanced line. The straightforward and typical way is by running a cable which has an unbalanced architecture, e.g., a coaxial cable. In such a case, breaking the shield will break the signal return path. I have not been able to trace down the Whitlock article mentioned; but I would be very surprised indeed if he's telling anyone to break a ground loop in an UNbalanced application by telescoping the shield.

Your reply mentions that there are different cable topologies, and mentions, for example, star quad and other mic cables. That's another matter. Cables of that sort are designed for use in balanced circuits; they have a symmetrical construction, with two signal conductors (or, in star quad, four conductors which are connected in pairs to make two) and a separate ground. Sometimes those cables are used in unbalanced circuits, and often the way that's done is to run one conductor (or one pair, in the star quad) with the signal, connect the other conductor to the ground, and then connect the shield to the ground also. In such a case, one can, of course, disconnect the shield at one end without interrupting the signal path, and perhaps that's what you are referring to. But doing this, you'll note, does NOT break up a ground loop. Why? Because that second conductor is still joining the grounds at both ends of the cable and completing the loop. When this is done, it is usually done not in an attempt to break a ground loop, which it can't do, but in an effort to control noise thought to be riding in on the shield.

I don't know the Whitlock article; but my suspicion would be that he is discussing use of telescopic grounds in BALANCED circuits. That isn't generalizable to unbalanced circuits, whether one uses a "balanced" cable topology or not.

I'm not a big fan of duelling by proxy or mere reliance upon authority, but since this discussion seems to be going on I should probably toss in what one of the leading authorities on audio, video and data cable has to say. Stephen Lampen, author of the Audio/Video Cable Installer's Pocket Guide and an electrical engineer/evangelist for Belden cable, says at p. 382-3:

"In the audio world there is a solution to ground loops called the telescopic ground. A telescopic ground only works with a cable that is a balanced line, that is, one that has two wires to carry the signal and a separate shield. In a telescopic ground, the shield is connected only at one end, which prevents the completion of the ground loop. It provides one path instead of two for noise and interference to go to ground, instead of two, so the noise reduction is less.

* * *

Telescopic grounds cannot be used in unbalanced circuits such as video coax because the shield is one of the two conductors necessary to send the signal. That is, the shield is both the noise-reduction portion of the cable and a signal path. Unground it and you will have the world's noisiest circuit if the signal gets through it at all. The other path, taking the place of the shield that was disconnected, will be established through some other ground path through other equipment! You might as well hang a single wire in midair as an antenna for noise and interference."