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Thread: Consumer and Pro-audio electronics: Connectivity

  1. #46
    Senior Member Don Mascali's Avatar
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    No offense taken, Bo. I know it's not the best stuff, but, beer budget and all that. Until I win the Lottery, it will have to do. Someday...

    Don M
    4406, 4412A, L100, L100t3 (3 pair), L1, L7, 4645C, 4660A, 4695B, SR4735 and various DIY JBL Pro loaded systems.

  2. #47
    Senior Seņor boputnam's Avatar
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    Benefits of same AC circuit

    Revisiting an old thread...

    One thing not covered here is the benefit of running on the same AC circuit. Intiuition sez it shouldn't matter in one's home, but since I run into the GL problem constantly in small clubs, when the band backline is on a different AC Edison plug than I am (for load reasons), I frequently encounter GL's. Since all gear is three-wire AC, most remedies require merely a DI between the snake and the stage gear. But for really testy gear that simply will not stoptheir quiet humming no matter what is tried, I plug them into my AC circuit and hope the breaker will hold - this always remedies the problem.

    At home, I've been struggling a number of years with a GL between the TV and system. I've used various types of DI's, and have reduced the symptom, but the quiet hum wouldn't completely leave. I've gotten to kinda like it, but the wifey, not. The TV and system are on two sperate AC circuits So, I tested running an extension cord to the amp rack and "bingo", hum gone. Noise floor remarkably reduced. So, I clipped one end of the 14 gauge extension cord, and ran it through the hole in the floor along with the system cable bundle that runs under the house, ending in the amp rack domain and am finally free of this hassle. This is exactly what is done at shows, where I must run the console on the same circuit as the amp racks to avoid GL's, so I run AC from stage along side the snake.

    Clearly, even though the TV and system were on the same breaker box, by being on two different circuits there were two paths to ground, and the TV didn't like it.
    bo

    "Indeed, not!!"

  3. #48
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    Re; same AC circuit

    Very important stuff, Bo.

    I'd add/clarify that while having everything on the same branch circuit will solve many problems, one really only needs to connect to the same "leg" or phase of the house wiring to enjoy all the benefits you mentioned, while not creating any overloading of a single circuit.

  4. #49
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by moldyoldy View Post
    I'd add/clarify that while having everything on the same branch circuit will solve many problems, one really only needs to connect to the same "leg" or phase of the house wiring to enjoy all the benefits you mentioned, while not creating any overloading of a single circuit.
    That's not always the case. The reason for the hum is the resistance in the neutral to ground connection... the ground potential has to be the same for each circuit... hence "star grounding"... in any event the easiest solution is to have a single circuit with a large current capacity and to plug the entire system into it. When everything has the same ground potential there is no hum and usually no RFI.

    Using different legs is an even larger issue... It is interesting how many people, electricians included, who don't understand this. I have two "audiophile" friends who have wired dedicated circuits into their listening rooms. Both of them have used separate legs for each side of the room and plug one mono block into each leg... their idea is similar to that of the distortion reduction in a push pull amp... in this case, added noise is the result.


    Widget

  5. #50
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    Quote Originally Posted by Mr. Widget View Post
    That's not always the case....
    Good point, and entirely true. Should be a requisite for new construction/installs. From the frugal, Q&D POV of a lowlife renter (myself) or Head Roadie though, finding the right combinations of outlets to use quickly solves the big problems.

    Slight variances in potential-to-ground between 'house legs' is a common noise source that begins outside at the xfmr, beyond our control. That leaves same-circuit as the solution for centrally-located gear, and same-phase the best option for scattered, remote gear.

    Hadn't bumped into the "push-pull" crowd yet. Another reason I live in the sticks...

  6. #51
    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by Mr. Widget View Post
    The reason for the hum is the resistance in the neutral to ground connection... the ground potential has to be the same for each circuit... hence "star grounding"...
    Yup. It matters SO much.

    With my "current" current connection, the noise floor has dropped at-least -2 dB, likely more. It also seems to have cleared-up the Video sound, as if the GL was somehow muddying the FR.

    I'm certain someone here could explain what happens to the signal when a GL is present...
    bo

    "Indeed, not!!"

  7. #52
    Senior Member macaroonie's Avatar
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    Estabish a technical earth or ground. Put a copper spike into the dirt under your house and connect all the relevant grounds to that with at least 6 mm cable. take a pee on the ground where the spike is .... salts connectivity etc.
    There are loads of web sites that can give you chapter and verse on this.

  8. #53
    Senior Member just4kinks's Avatar
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    Cheap solution

    I know this is an old thread, but I'd like to chime in, because I recently fought through these problems myself. I have a coax cable line coming in, 3 consumer 2-prong units, 2 pro power amps, and a 3-prong projector for the TV. I was getting a nasty hum and lines in the TV image.

    I researched ground loops for a while... I was about to spend a lot of money fixing the problem, but I decided to try the easy way first. I basically just got a bunch of 14 gauge wire, crimped some connectors on, and connected all the cases together. I also grounded into the coax cable, at a nearby splitter box. It worked perfectly, my system is now dead silent and the TV picture is perfect.

    There might be situations where it won't work, but it's at least worth a try. Some of those ground loop isolators can get pretty pricey.

  9. #54
    Senior Member Audiobeer's Avatar
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    Hum that I had came from my components all of which are grounded and noise-free on their own. Then I brought my cable into the mix. My ground at the house should have zero volts AC and DC however, there's usually a very small amount of voltage present in a ground. This in itself does not necessarily cause hum, but if two devices are connected to grounds where there's a difference in electrical potential between them, current will flow through one ground wire to the other, developing a voltage whose flow is audible as hum.
    When you connect different components to different circuits, you frequently get hum, since each circuit's ground will probably be just a smidge off of zero volts AC and DC. If everything is connected to a component that is grounded, you can sometimes "cheat" your grounded plugs on everything else and solve your hum problem. . That could be a recipe for disater. But that cable TV connection, what a piece of %$^&! . The coaxial cable that I have in my house is grounded via its shield and that's grounded at the cable provider's Box. Different circuits in the same house can have ground planes that differ in voltage. Do you that something grounded Down the street a bit from my house has the same potential? Not likely.
    You can by a grounf isolater and in fact you can make your own. I copied a lot of the above theory from the internet to explain my problem.

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