Badger
Active member
Re: Re: Re: "Phase" in a Patchbay
Yeah, the problem is most people think that ground is some magical constant that all electricity goes to. Its not. each source has an out and an in, and it has to have a complete path from one side to another for current to flow. Voltage is the electrical differance between two points in the circuit. Any two points, not just the input and output of the source. So if you have two speakers wired in series, you could mease a voltage across just one of them, even though the curant is flowing through both.
Anyway, so if you put a scope on the end of that patch chord, and attatched one lead to the sleeve, and the other to the tip, the wave form you would see is a graph of the electrical differance between the sleeve and the tip. it will swing positive, then negative then back positive. If you reverse the wires, it will show the same waveform, but it will swing negative, then positive, then negative...The reverse. The signal is the differance between the two, not the differance between the tip and "ground", because there may not be any electrical connection between the ground for one device and the ground for another.
See, your computer case is connected to that third prong on your wall outlet, which is connected to a pipe driven into the ground. But your computer doesnt use this unless something goes horribly wrong. This is a safety feature so that if the ac line somehow shorts to the case, you wont shock the crap of yourself. Ever notice that when somebody cuts the third plug off of an extension cord so it will work in a two prong outlet it still works? Thats why. BTW this ground connects through the soil to a similar pipe driven into the ground at an electrical substation near you, so thtat it can complete the ciruit and prevent you from dying.
Now back to our drum machine example. If your drum machine runs off a wall wart, then its not connected to that earth ground. The wall wart is, maybe, sometimes, but not always. The drummachine is running of a low current dc voltage usually, so there is no shared ground between it and the computer case. Now depending a lot of factors involved in how the ciruit is designed there could be some electrical relationship between the two, but not a straight short and not usually. But tow totally take that out, I used to have a drum machine that ran off of batteries. In that case there is abolutely no electrical connection to what drum machine considers ground, and what the computer would consider ground.
So depending on the hardware, how its designed, reversing the tip/sleeve sleeve tip wiring may or may not short to ground. For another screwed up example. So say my sampler, that runs off of a three prong cord just like the computer, and has that earth ground connected to its chasis for safty, were designed cheaply so that the sleeve on its 1/4 inch jack were soldered directly to the chasis, and say I had a really cheesy sound card that the sleeve on its input were soldered to the bracket that screws into the chasis of the computer, then yes it would short the hell out of the signal, and we would get nothing. Quality elctronics are usually not designed that way, but some stuff is.
sjjohnston said:
Yeah, the problem is most people think that ground is some magical constant that all electricity goes to. Its not. each source has an out and an in, and it has to have a complete path from one side to another for current to flow. Voltage is the electrical differance between two points in the circuit. Any two points, not just the input and output of the source. So if you have two speakers wired in series, you could mease a voltage across just one of them, even though the curant is flowing through both.
Anyway, so if you put a scope on the end of that patch chord, and attatched one lead to the sleeve, and the other to the tip, the wave form you would see is a graph of the electrical differance between the sleeve and the tip. it will swing positive, then negative then back positive. If you reverse the wires, it will show the same waveform, but it will swing negative, then positive, then negative...The reverse. The signal is the differance between the two, not the differance between the tip and "ground", because there may not be any electrical connection between the ground for one device and the ground for another.
See, your computer case is connected to that third prong on your wall outlet, which is connected to a pipe driven into the ground. But your computer doesnt use this unless something goes horribly wrong. This is a safety feature so that if the ac line somehow shorts to the case, you wont shock the crap of yourself. Ever notice that when somebody cuts the third plug off of an extension cord so it will work in a two prong outlet it still works? Thats why. BTW this ground connects through the soil to a similar pipe driven into the ground at an electrical substation near you, so thtat it can complete the ciruit and prevent you from dying.
Now back to our drum machine example. If your drum machine runs off a wall wart, then its not connected to that earth ground. The wall wart is, maybe, sometimes, but not always. The drummachine is running of a low current dc voltage usually, so there is no shared ground between it and the computer case. Now depending a lot of factors involved in how the ciruit is designed there could be some electrical relationship between the two, but not a straight short and not usually. But tow totally take that out, I used to have a drum machine that ran off of batteries. In that case there is abolutely no electrical connection to what drum machine considers ground, and what the computer would consider ground.
So depending on the hardware, how its designed, reversing the tip/sleeve sleeve tip wiring may or may not short to ground. For another screwed up example. So say my sampler, that runs off of a three prong cord just like the computer, and has that earth ground connected to its chasis for safty, were designed cheaply so that the sleeve on its 1/4 inch jack were soldered directly to the chasis, and say I had a really cheesy sound card that the sleeve on its input were soldered to the bracket that screws into the chasis of the computer, then yes it would short the hell out of the signal, and we would get nothing. Quality elctronics are usually not designed that way, but some stuff is.