Tyrsonswood

I don't think you would be using anything inside a house where this would have any relevance, but that being said, look at it this way. An extension cord is part of a cyclic "send and return" situation...... so a 50 foot cord is 100 feet of resistance. ("send and return" isn't exactly correct either, but fits for this explanation.)

In a normal household situation

1. you wouldn't have anything connected to an extension cord that draws enough current for length to have any effect. (unless you have an under size cord trying to run a refrigerator or air conditioner.... something like that. Everybody knows this is a No No, right?)

2. With normal sound/computer gear you would have to have an extension cord of extreme length before you ran into any problems...... (or a really flimsy cord, but I don't think they make long cords with 14ga, or smaller, wire due to safety concerns) And you should never use extension cords plugged into extension cords for added length either....

3. In reality if someone were to plug all their gear into a very long cord and it were drawing to much amperage for the situation, I think the cord would fry before there was a noticeable degradation of sound..... I don't know, I've never tried it.

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blitter2

Tyrsonswood, please what change in resistance makes, using a non continues cable to wall socket but one plugged via an extension cord or power strip?

The "cut" of power cord instead of using a continues one.

Resistance loss or gain compared with the continues cable? The "cut" that is.

That is if the extension's cord resistance is not of importance. I am only interested what the non continues cables does to resistance.

Tyrsonswood

Any connector adds resistance, each foot of wire adds resistance....... These are usually minimal but do add up with multiple connectors and very long runs. What this can cause in extreme instances is excessive heat in the wire and current loss so the unit being powered may malfunction or just not turn on.

One connection per end and a short cord will have no effect.

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blitter2

Thank you Tyrsonswood.

blitter2

Tyrsonwood, do RFI/EMI filters add resistance to the devices that are connected output resistances or do the filters just use it as a resistance differencial trick to just work?

I am asking becauase I know an 30db filter uses 0.8 ohm and an 70db uses 0.4 ohm but I am not sure if this resistance is added to the devices connected.

Tyrsonswood

I think that resistor is in series, so yes it would.

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blitter2

Tyrsonswood, please can the heat of a radiator if cables are near, cause the excessive heat in the wires and current loss effect you mentioned?

Tyrsonswood

For safety reasons you're not supposed to run extension cables near heaters or radiators anyways, in the US I believe it says so right on the warning label attached to the cord..... but to answer the question it's more like the resistance causes the heat in the cases I was mentioning, not the other way around. From an engineering standpoint heat can increase resistance in a wire or component as well.

I can't see how any of this has any relevance to hooking up a sound system to a Live! card though.

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blitter2

Tyrsonswood hi , merry christmass and happy new year.

In amps. There is a connector containing a signal ground and a chaisis ground cable for the amp to get signal and chaisis safety ground.

The chaisis cause of metal construction needs safety ground to prevent electrocution.

I have removed the safety ground cable on my diy amp power bar, for having one single ground point for my amp, via the signal cable to prevent ground loops.

The ground-signal connector of my amp is soldered to the chaisis. But what is that connector responsible for now? The amp is not getting satety ground (or does it via the signal cable coming from the pc?).
Is it maybe now its use is that it gives ground to signal and maybe as well ground to chaisis?

Please do chaisis needs ground at all? Or chaisis in general only use safety ground for the electrocution purposes?

Does signal via that connector needs safety ground for noise rejection to work or just ground? If it only needs ground I already have one via the signal cable. (or do I have safety ground as well coming from the pc?).

Sorry for the long post but webpages confuze ground and safety ground a lot by calling both ground and I am confuzed.

Tyrsonswood

Are you even getting ground loop hum with safety ground properly connected? Don't mess with this unless you are having problems to begin with.

First of all the chassis should always be grounded and not rely on signal ground to do so. This is safety ground, if your amp has a 3 prong plug all 3 prongs must be connected. If it's just two prong then it's double insulated and this is not an issue.

Second The signal ground may or may not also be connected to the chassis depending on hum in the system. This is where any change (ground lift) would be made and it's inside the amp. If it's a pro level amp it likely has a switch for this. If it's not then there could be a lot of modding necessary to make this happen inside the amp and at the cable jacks to isolate the signal ground from the chassis ground. (IF NEEDED..... Don't mess with it if you don't need to)

I've got 5 systems in my loft with 3 separate amps, three racks of preamps and effects, misc guitar amps and pedals all over the place and nothing needs to have any "ground lifts"..... I think you are chasing something that doesn't exist and risking safety and or equipment in the process. Be careful man, please.

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blitter2

Tyrsonwood thank you for your reply.

Please does the signal ground connector only redirects the noise that exists in signal cable shieldings, or it also redirects noise from non shielded signal cables?

Tyrsonswood

The signal ground completes the circuit, in a properly shielded coax cable it can also use this ground as a shield to block outside signals from the hot wire. In other words the ground takes on dual purpose in a coaxial cable. A twisted pair or even two discrete wires, which is I believe where this thread started, will carry the signal, but produce no shielding so could be noisy. A poorly designed coax cable or a twisted pair is not 100% shielded so can allow for some noise, it's the 100% coverage that does the trick.


("coax cable" or coaxial cable such as guitar cable, RCA-RCA stereo cable, 1/8 " TRS Mini jack-whatever stereo cable, etc. etc. Audio stuff. I add this because I noticed when googleing "coax" I get mostly hits about video cable which is a different but related science and filled with a bunch of "math" that doesn't apply to audio analog signals)

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