Shielded speaker cable? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 24 Old 06-16-2019, 09:15 PM - Thread Starter
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Shielded speaker cable?

Is there specifically designed audio cable with shielding that can be run through a wall?

I found this control wire, and similar in other brands: https://www.monoprice.com/product?p_id=38766

Is that adequate? I have some runs where I will have to come close to AC power lines and near dimmer modules. Any recommendations for speaker cable? Design is more important than brand.
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post #2 of 24 Old 06-16-2019, 09:27 PM
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If you really need high isolation then Canare star quad (e.g. 4S11, 4S12) cables run in conduit should do it.

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post #3 of 24 Old 06-17-2019, 09:57 AM - Thread Starter
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That's a pricey cable for a $40 in-wall speaker with only 2 binding posts. Better to use a quad cable and bind the pairs together, I take it? Should be able to back off to around 18 gauge or even less, I would think.

What kind of conduit? The metal spiral type?
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post #4 of 24 Old 06-17-2019, 10:44 AM
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If I want to have a long run from my 2-zone amp for one of the zones, is there any reason to NOT use the Canare 4S11 or equivalent 4-wire cable to carry both channels?
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post #5 of 24 Old 06-17-2019, 07:51 PM
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Originally Posted by DonH50 View Post
If you really need high isolation then Canare star quad (e.g. 4S11, 4S12) cables run in conduit should do it.
"While the above discussion [star quad configuration of balanced lines] focuses on preventing noise from getting in (e.g. into a microphone cable) the same star-quad quadrupole configuration is useful for audio speaker cable,[10] for split-phase electric power wiring, and even for open-wire star quad transmission line.

In these cases, the purpose of the star quad configuration is reversed. The star-quad geometry cancels the magnetic fields that are produced by the two pairs of conductors. This cancellation reduces the magnetic emissions of the cable."
[bold text emphasis mine]

Source: https://en.wikipedia.org/wiki/Star_quad_cable
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post #6 of 24 Old 06-17-2019, 07:57 PM
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Originally Posted by ScottAvery View Post
Is there specifically designed audio cable with shielding that can be run through a wall?
Not that I'm aware of, however most certified in-wall wiring uses a twisted pair, a spiral helix like a barber's pole, for adequate EMI/RFI sheilding. Unless you do something wacky like drape your spkr. wire over the back of an active microwave oven or live at the base of a giant AM radio antenna transmission tower, you should be good to go with just that twist [originally invent by Alexander G. Bell to minimize noise picked over miles and miles of telephone transmission wires].

Also it is never a good idea to run adjacent to and paralell to AC lines. Cross over them at right angle when you must.
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post #7 of 24 Old 06-17-2019, 08:39 PM
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@ScottAvery : Here is an article from Belden about the star-quad configuration: https://www.belden.com/blog/broadcas...Starquad-Works Using that configuration increases capacitance but provides better rejection of EM fields (noise). The Benchmark website also has a number of articles and videos explaining the advantage of that configuration (e.g. https://benchmarkmedia.com/blogs/app...stration-video). The interleaving (twisting) of the conductors provides common-mode rejection of impinging noise (it also reduces radiation from the cable but that is not normally a concern for audio). Often (mostly) used for microphones, Belden, Canare, Mogami, and others make heavy-gauge versions for speakers as well (the Canare cables I cited are for speakers). Since impedances are low most speaker cables do not have (nor need) additional shielding (perhaps all; I don't recall a shielded speaker cable off-hand).

Conduit is usually not the corrugated/spiral type in-wall (unless it needs to have a complex bend) but rather just straight tubes cut to fit. Unless you have really bad noise problems you should not need it, but not all star-quad cables are rated for in-wall use (CL2 or CL3). In-wall cables utilize special insulation that is more fire-resistant and/or less toxic than typical cables. Your local code may require in-wall cables, even "low-voltage" speaker cables, to be in conduit if they are not CL2/CL3 (in-wall) rated.

AC lines can emit significant EM fields but are generally low-frequency so a little distance, perhaps 6"~12", may be enough to isolate the speaker cables from the AC lines. Dimmers are a wideband noise source and are often as likely to cause RFI (e.g. AM radio frequency) interference as line noise from all the switching noise they inject into the AC lines.

Cost is up to you but there are a number of star-quad cables; shop around. Make sure they actually have the twisted conductors; not all quad cables do. You might replace your $40 speakers someday, and even if not, noise is just as annoying frm cheap speakers as from expensive speakers.

@MTVhike : I am not sure exactly what you are asking. If you run two speaker pairs through a single quad cable you give up the noise rejection properties of the star-quad configuration. If you are talking about using a pair of star-quad cables for two speakers that will work just fine. The biggest disadvantage, other than cost, is the higher capacitance of star-quad cables. That is usually insignificant for a speaker run (and microphone runs, for that matter; I have run several hundred feet of mic cable without loss and with good noise rejection in a channel that included mic, line, speaker, and power cables albeit with some shielding of the other cables).

Another alternative is to use RF coax like RG-8 but it can be harder to work with and may cost the same as star-quad speaker cable.

HTH - Don
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post #8 of 24 Old 06-17-2019, 09:38 PM - Thread Starter
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Originally Posted by m. zillch View Post
Not that I'm aware of, however most certified in-wall wiring uses a twisted pair, a spiral helix like a barber's pole, for adequate EMI/RFI sheilding. Unless you do something wacky like drape your spkr. wire over the back of an active microwave oven or live at the base of a giant AM radio antenna transmission tower, you should be good to go with just that twist [originally invent by Alexander G. Bell to minimize noise picked over miles and miles of telephone transmission wires].

Also it is never a good idea to run adjacent to and paralell to AC lines. Cross over them at right angle when you must.
Its a build in a finished space with arches and other features that will require me to pull speaker cable through wall right next to several dimmer switches and multiple AC circuits. There is no reasonable alternative route.
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post #9 of 24 Old 06-17-2019, 09:54 PM
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The old style dimmers pre I'd say ~1995 were very problematic but I think modern ones like Lutron aren't nearly as bad. [And largely the noise they injected was into your AC lines.]

I have this remote control dimmer, and have its IR code in my Harmony Universal remote. Works great.

Also keep in mind speaker wire signal is a strong robust signal, unlike a low level preamp signal or even worse a mic or phonograph signal. Stereo systems are much more easily corrupted by external noise when the signal is weak.

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post #10 of 24 Old 06-18-2019, 11:28 AM
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Xtz has star quad cables I guess made on receipt from belden Canare for 49 bucks

Edit sorry this is short stereo terminated wires.

I suggest you ask Supra from Sweden, they make a wide variety of speaker cables cheap, or bluejeans in the states if that is more convenient.
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post #11 of 24 Old 06-20-2019, 04:44 PM
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Quote:
Originally Posted by ScottAvery View Post
Its a build in a finished space with arches and other features that will require me to pull speaker cable through wall right next to several dimmer switches and multiple AC circuits. There is no reasonable alternative route.
Just run the speaker cables thru a short length of metal conduit near the dimmers. Don't even worry about connecting it to the Safety Ground.

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post #12 of 24 Old 06-25-2019, 11:50 AM
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another simple solution forget the wires

https://www.amazon.com/Klipsch-WA-2-.../dp/B005WLYGCU

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post #13 of 24 Old 06-26-2019, 08:00 AM
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Speaker wire doesn't need shielding. Induced noise on high impedance lines can be audible because the current transfer on high impedance lines is low. Speaker wires are low impedance and any induced voltage from any normal source is not going to support enough current to affect the signal. When you load a power supply with too low an impedance / try to draw too much current, the voltage has to drop. It's the same with induced noise on a speaker wire. You can try to induce a voltage on the line, but the impedance is so low that the induced voltage falls to negligible levels because it won't be able to drive that voltage at the current the speakers would take. You would have to have a very very very strong magnetic field to induce enough voltage and power into a speaker line for it to be even slightly audible.


Some other replies here seems to have misunderstood the question as being about high-impedance line-level signals. That's a different story.
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post #14 of 24 Old 06-27-2019, 11:14 AM
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Originally Posted by DonoMan View Post
Speaker wire doesn't need shielding. Induced noise on high impedance lines can be audible because the current transfer on high impedance lines is low. Speaker wires are low impedance and any induced voltage from any normal source is not going to support enough current to affect the signal. When you load a power supply with too low an impedance / try to draw too much current, the voltage has to drop. It's the same with induced noise on a speaker wire. You can try to induce a voltage on the line, but the impedance is so low that the induced voltage falls to negligible levels because it won't be able to drive that voltage at the current the speakers would take. You would have to have a very very very strong magnetic field to induce enough voltage and power into a speaker line for it to be even slightly audible.


Some other replies here seems to have misunderstood the question as being about high-impedance line-level signals. That's a different story.
Interesting..

How much magnetic field do you need to affect the signal in your opinion?

Normal power wires and pads have pretty big field, and in my home it's alot of them.
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post #15 of 24 Old 06-27-2019, 12:47 PM
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Interesting..

How much magnetic field do you need to affect the signal in your opinion?

Normal power wires and pads have pretty big field, and in my home it's alot of them.

I don't know, but I can tell you that any given voltage run into an 8 ohm load will require 1250 times the current (and power) as it would into a typical 10k ohm load (10k input impedance is a common value for line-level inputs) or the induced voltage will drop below what it would otherwise have been. Typical mains wiring in a house doesn't give off that big a magnetic field. Magnetic fields will follow the inverse square law and also you have to take the angles of your speaker and mains wiring into account as if you cross the two at a perfect 90 degrees there is no induced voltage at all. Of course you won't be able to keep your speaker wire from ever deviating from being perpendicular to the mains wiring but if you cross the wires only at 90 degrees (or close) and keep any parallel runs a reasonable distance apart, induced voltage will be minimal. Only specialized cases like maybe high voltage wires, or a high power RF transmitter (which would actually use high voltage wires anyway) very close by would maybe present an issue with speaker wires.


I realize this answer is probably not as detailed as you're asking but unfortunately I can only explain this to a certain level of detail.
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post #16 of 24 Old 06-27-2019, 01:48 PM
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I don't know, but I can tell you that any given voltage run into an 8 ohm load will require 1250 times the current (and power) as it would into a typical 10k ohm load (10k input impedance is a common value for line-level inputs) or the induced voltage will drop below what it would otherwise have been. Typical mains wiring in a house doesn't give off that big a magnetic field. Magnetic fields will follow the inverse square law and also you have to take the angles of your speaker and mains wiring into account as if you cross the two at a perfect 90 degrees there is no induced voltage at all. Of course you won't be able to keep your speaker wire from ever deviating from being perpendicular to the mains wiring but if you cross the wires only at 90 degrees (or close) and keep any parallel runs a reasonable distance apart, induced voltage will be minimal. Only specialized cases like maybe high voltage wires, or a high power RF transmitter (which would actually use high voltage wires anyway) very close by would maybe present an issue with speaker wires.


I realize this answer is probably not as detailed as you're asking but unfortunately I can only explain this to a certain level of detail.
In my situation I have two main power pads cheap with button and speaker wire on top of this, abit too long for my setup now and I try to keep it apart, but strangely everytime I clean they always lies rolled and twisted together in a salad behind the bench.
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post #17 of 24 Old 06-27-2019, 01:51 PM
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And if you take a meeter near it, it screams like Chernobyl meeter.

But I'm no expert.

If there is anything about shielded power chord it must be this magnetic disturbance..

But if this is audible or psychology I don't know.
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post #18 of 24 Old 06-28-2019, 11:22 AM
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The issue with long speaker cables and the need for shielded usually relates to EFI/RFI getting on the lines back into the amp to get demodulated after the feedback path. That is, or at least was, a common problem even in home installations if they were near an RFI source (dimmer, fan, HVAC, fridge, or even a radio tower nearby; home workshops with power tools and amateur radio stations were another common source). The output impedance of an amplifier goes up at higher frequencies as loop gain drops (less feedback, higher-impedance output).

The (at least my) responses to shielding were biased toward the nearby dimmer and unknown run length. Using shielded cables, star-quad, or even conduit now lessens the risk of problems later. If they were laying on the floor I 'd say try anything, but once in the walls replacement and repair options are much more limited.

IME/IMO - Don
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post #19 of 24 Old 06-28-2019, 12:02 PM
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Quote:
Originally Posted by ScottAvery View Post
Is there specifically designed audio cable with shielding that can be run through a wall?

I found this control wire, and similar in other brands: https://www.monoprice.com/product?p_id=38766

Is that adequate? I have some runs where I will have to come close to AC power lines and near dimmer modules. Any recommendations for speaker cable? Design is more important than brand.
If you really want some shielding (for some reason) buy cable for 3 phase VFD motors that have a shield and use that as audio cable.
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post #20 of 24 Old 06-28-2019, 12:28 PM
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Originally Posted by DonH50 View Post
The issue with long speaker cables and the need for shielded usually relates to EFI/RFI getting on the lines back into the amp to get demodulated after the feedback path. That is, or at least was, a common problem even in home installations if they were near an RFI source (dimmer, fan, HVAC, fridge, or even a radio tower nearby; home workshops with power tools and amateur radio stations were another common source). The output impedance of an amplifier goes up at higher frequencies as loop gain drops (less feedback, higher-impedance output).

The (at least my) responses to shielding were biased toward the nearby dimmer and unknown run length. Using shielded cables, star-quad, or even conduit now lessens the risk of problems later. If they were laying on the floor I 'd say try anything, but once in the walls replacement and repair options are much more limited.

IME/IMO - Don

The load of the speaker is still going to mostly-short-out any RFI. The closest point of induction does not simply send a voltage signal both ways down the cable where it will enter the amplifier's output at its usual voltage. It will split according to Kirchoff's Laws. Almost all the current the RFI produces will travel to the speaker and its voltage will be pulled down, which also affects the voltage that makes it back to the amp. Dimmers aren't exactly switching at super high frequency either. Probably 100-250kHz or so. Take a tweeter I like, the Vifa/Peerless XT25, rated 0.01mH. It has a reactance of 6.3 ohms at 100kHz and about 63 ohms at 1MHz (assuming no lowpass filters in your speaker crossover for the tweeter, anyway). Still going to pull most normal sources of RFI way down in voltage. Will some make it back to the amplifier? Yes. Is it possible for it to cause a problem? Yes. How likely is it? In most homes, extremely unlikely.

But hey, I won't say don't do it. I'll just say I wouldn't (and never have). Hell, my speaker wires, currently not in-wall (but I've done in-wall in multiple setups), are parallel to power cables, with very little separation. No problem at all. Edit: I have a dimmer about 10 feet away and another about 20 feet away. And there is a difference between 10 feet and 4 inches in that regard, I do get that.

I do like conduit, though!

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post #21 of 24 Old 06-28-2019, 12:49 PM
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The load of the speaker is still going to mostly-short-out any RFI. The closest point of induction does not simply send a voltage signal both ways down the cable where it will enter the amplifier's output at its usual voltage. It will split according to Kirchoff's Laws. Almost all the current the RFI produces will travel to the speaker and its voltage will be pulled down, which also affects the voltage that makes it back to the amp. Dimmers aren't exactly switching at super high frequency either. Probably 100-250kHz or so. Take a tweeter I like, the Vifa/Peerless XT25, rated 0.01mH. It has a reactance of 6.3 ohms at 100kHz and about 63 ohms at 1MHz (assuming no lowpass filters in your speaker crossover for the tweeter, anyway). Still going to pull most normal sources of RFI way down in voltage. Will some make it back to the amplifier? Yes. Is it possible for it to cause a problem? Yes. How likely is it? In most homes, extremely unlikely.

But hey, I won't say don't do it. I'll just say I wouldn't (and never have). Hell, my speaker wires, currently not in-wall (but I've done in-wall in multiple setups), are parallel to power cables, with very little separation. No problem at all.
That has not been my experience -- I have had numerous RFI cause problems with long runs in both professional and consumer installations. Unlikely, yes, but it is up to you (or the OP) to decide if the risk is low enough to not worry about for an in-wall installation. (If it were not in-wall I wouldn't worry as it's easy to fix in the rare case it is a problem -- I do agree it is very rare, but when I'm the one who has to fix it...) Most amps include an RF filter at the output as well as the input but not all, and at a few hundred kHz the output impedance is likely to be high enough that RFI can couple through the feedback network, get demodulated at the input, and gained up through the amp.

Power cables are not the problem except to the extent they serve as antennae for RF interference.

Sounds like our experience just differs, I'll let it lie. - Don

p.s. My biggest argument for conduit is actually not RFI, it is the rare FUBAR case where the speaker cables were shorted or -- and this is the one I always remember -- someone connected the speaker lines to AC power and a short caused them to melt their insulation and start a fire. It is not the 1 bazillion cases that worked without problem, it is that one really nasty failure that sticks with you (me).
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post #22 of 24 Old 06-28-2019, 12:56 PM - Thread Starter
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Thank you all for the education and support. I think I may just avoid the issue and build an external column to house the speaker rather than go in-wall. This will allow me to drop the speaker cable in from above and avoid all the AC lines and 5 dimmer switches in the narrow access space to that wall.
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post #23 of 24 Old 06-29-2019, 09:26 AM
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Thank you all for the education and support. I think I may just avoid the issue and build an external column to house the speaker rather than go in-wall. This will allow me to drop the speaker cable in from above and avoid all the AC lines and 5 dimmer switches in the narrow access space to that wall.
7-10 meters with normal good quality speaker cable I don't think you will have any problems.. As in to get music..

Whether your dimlights is noticable disturbing the sound quality I doubt....

It's not optimal maybe, but I guess it is functional and should be ok for enjoying music....

I've used 10 meters normal cheap quality trough electric hell and to amp.... Enjoying the music..


Of course it's a hobby tweaking, I do that myself..
But I believe it will work as long as you use right gauge...





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post #24 of 24 Old 06-30-2019, 01:22 PM
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The load of the speaker is still going to mostly-short-out any RFI. The closest point of induction does not simply send a voltage signal both ways down the cable where it will enter the amplifier's output at its usual voltage. It will split according to Kirchoff's Laws. Almost all the current the RFI produces will travel to the speaker and its voltage will be pulled down, which also affects the voltage that makes it back to the amp. Dimmers aren't exactly switching at super high frequency either. Probably 100-250kHz or so. Take a tweeter I like, the Vifa/Peerless XT25, rated 0.01mH. It has a reactance of 6.3 ohms at 100kHz and about 63 ohms at 1MHz (assuming no lowpass filters in your speaker crossover for the tweeter, anyway). Still going to pull most normal sources of RFI way down in voltage. Will some make it back to the amplifier? Yes. Is it possible for it to cause a problem? Yes. How likely is it? In most homes, extremely unlikely.

But hey, I won't say don't do it. I'll just say I wouldn't (and never have). Hell, my speaker wires, currently not in-wall (but I've done in-wall in multiple setups), are parallel to power cables, with very little separation. No problem at all. Edit: I have a dimmer about 10 feet away and another about 20 feet away. And there is a difference between 10 feet and 4 inches in that regard, I do get that.

I do like conduit, though!

Signals induced into speaker wire will likely be common mode since they will affect both conductors more or less the same. The speaker is unlikely to have much effect on this common mode signal since it will be on both inputs, and the speaker doesn't have a separate ground connection or differential amplifier to absorb much of this common mode signal.

At the amplifier end the common mode signal will be mostly converted to differential mode since each side of the signal will like encounter different conditions such as impedance. One side of the signal will see the low impedance outputs of the emitters of the power transistors, the impedance of an output inductor, if used, perhaps some capacitance to ground, and anything else attached to this conductor. This signal will also travel back through the feedback network that is connected to the output. The feedback network is likely connected to a ground and one of the inputs of the input differential amplifier in a typical design, through resistors and capacitors. There may other connections as well. It's hard to predict the result, which would be very frequency and signal level dependent, as well as dependent on the circuit design and physical implementation.

The signal on the other speaker wire conductor would first enter the amplifier ground. For reference, AVR's don't have a physical safety ground, they use two prong plugs. Most of the grounds in an AVR/AVP are ultimately connected together, although not all at the same point. Most of the grounds (various signal, digital, etc.) are also connected to the case at various points thorough small capacitors, something like 1 uF capacitors. There must be a lot of art in how all of these ground connections and signal flows are designed. The are also typically a connections from the case to each of the AC power inputs through small capacitors, around 1 uF, that are rated for this sort of safety critical location. One power input is essentially at earth ground, at least in the U.S., and other as 120 VAC. Since the outlet might be miswired, the capacitors are connected to both AC input lines. The idea is to dump collected high frequency noise, especially from the switch-mode power supply, into an earth ground.

The ground connections described above mean that noise introduced on the ground side of the speaker connector can go about anywhere and do what it will do. It's a tribute to the people that design AVR's and AVP's that there are few reported problems with noise that comes back through speaker wires, in instances when this happens, or most other entrances for that matter.
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