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Need Help,Speaker system humming

 

New member
Username: Badman5

IL

Post Number: 1
Registered: Sep-12
i Googled around but i cant fix the problem so i came to this forum.
My speakers are making a humming sound. What i have learned it may be an earth ground something problem. Long story short i pieced 2 car speakers 2 big infinity speakers and a Yamaha rx-v670 and a subwoofer from yet a third sound system. I have had no problems until i plugged in this cable i just bought: http://www.ebay.com/itm/2x-1-2M-3-5mm-Male-Plug-To-2-RCA-Male-Stereo-Audio-Adapt er-Cable-For-iPod-MP3-4-/261095690299?_trksid=p2047675.l2557&ssPageName=STRK:MEW NX:IT&nma=true&si=7X31SFetrySW6Y210PeCP1eDT1Y%3D&orig_cvip=true&rt=nc (ebay item number: 261095690299)
What i want to do is hook up this system to my pc. Curently there is only a 5 disc cd player installed. Any questions or screenshots needed just ask. Thanks guys.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17404
Registered: May-04
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First, I'm going to assume the speakers and sub are passive designs lacking their own amplification. Correct? If that is not the case (speakers and/or sub have built in amplifiers) , we have other issues to contend with. If it is so, we can proceed to ...

You have an open ground or, more likely, a ground loop. Not that surprising really, considering the system configuration. I assume the cable you are referring to is the RCA shown on the page with a dozen other choices. That would be, corrrect me if I'm wrong, the cable that makes everything work?

There are no easy solutions to this, the process is simply one of tracing down where the ground issue exists. The first thing to do is make sure the Yamaha is operating as it should. The receiver has a tuner (radio) function so attach an antenna and use the tuner and a single pair of speakers - no subwoofer - to make certain the receiver is not at fault and in need of repair. If the receiver checks OK, then you have to find where the grounding has failed.

To repeat, there are no simple ways to go about this. It is a process of going down the signal path and logically eliminating each possibility.

You hook each component up as simply as possible and when you find you have a noise you assume the issue is within the circuit you have just completed. You'll do best if you have a VOM or digital meter to check continuity of any cable though it is rather unlikely the cable is at fault if it's new out of the packaging. Older cables which have been in use are less certain.

My first suspicion would be the problem exists in the AC ground plane between the receiver - which has a two pronged AC plug - and the computer - which has a three prong ("grounded") AC plug. That does not mean you start here. You start at the front of the system and work your way to the AC plugs by eliminating every other possibility in front of the AC plugs.

The receiver has a (two conductor) ground to chassis connection while the computer has a (three conductor) floating ground path. There really isn't a good solution if this is the problem as you would endanger the computer by disabling the three prong ground of the computer. However, if you're running the signal to the receiver and from the computer by taking the signal at the sound card's RCA outs, this is less likely to be the case. Still, that's what I would check first as the computer probably doesn't like your Yamaha. If this appears to be the problem, then you must start to accept the fact that sound card is not going to work with that receiver. There are other alternatives for getting a signal to the receiver but they will all cost some money.

Temporarily lift the AC ground of the computer with a ground lift adapter purchased at any home improvement store for about $1 and possibly you'll find this is a (not too permanent) cure. You do not want to run a device with a grounded AC plug with that ground lifted if you want a sensitive device such as a computer to not be corrupted by surges. However, if that solves your problem and you're using the sound card's RCA outs, then possibly a different sound card or a sound card taken from a USB port would be your answer. USB sound cards run a few bucks at any audio/computer shop selling electronics.


Sorry to say, there are no simple answers to grounding problems.

When I say "grounding problems" I assume you are hearing a 60Hz ground hum and not a 120Hz circuit buzz. This makes a difference as 120Hz noises are seldom related strictly to grounding issues. 60Hz is what I would expect from your hook up and for that you need to do some research on the internet with "tracing ground loops" as your search wording. If the noise is 120Hz in nature, then I would expect a malfunction within one of the two devices being connected with the receiver being the more likely to be at fault and in need of repair. You are making your connection at the receiver through the "AUX in" RCA's, right? If so, try another line level input on the receiver such as "CD in" just to make sure it's not a problem with the specific jacks you are connecting to. Obviously, you do not want to make a connection to any "Phono in" jacks.

Make sure the receiver and the computer are on a the same AC circuit to begin with by plugging both into a surge protection strip. That has the best chance of placing both components on the same ground plane. That does, however, also present the problem the two components do not want to share the same ground plane at their AC inputs. (You can try reversing the orientation of the receiver's AC plug but that will require shaving off the polarizing ears of the plug [which is not truly a safe fix] or buying a ground lift adapter and doing so to it's ears to use as an intermediary device between the receiver's AC plug and the AC outlet.)

There's no way to tell until you experiment and test the waters. If there were a better answer, this would be simple. It's unfortunately not. But, if the noise is 60Hz in nature, the problem is a ground issue - either an open ground (unlikely) or a ground loop (very likely). You'll just have to do the work to figure out which it is in your system and then correct it accordingly.

Considering the cobbled together nature of your system, I assume cash is an issue. If not, then buy a small amp designed to be used with a computer and this should solve your problem ASAP. Your Yamaha simply doesn't like (not) sharing grounds with your computer. Another alternative would be to buy a USB DAC with RCA outputs. This would replace the sound card's output and also provide better sound quality in most cases. You can find USB DAC's on line for about $29 up to several hundred dollars. Using automotive speakers and a cobbled together sub, you won't detect any real difference between the cheapo and the champagne DAC's.



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New member
Username: Badman5

IL

Post Number: 2
Registered: Sep-12
Im not home yet buy when i get home i will try plugging in the receiver to the same outlet as the computer. I will add more details later. This is my system layout.
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New member
Username: Badman5

IL

Post Number: 3
Registered: Sep-12
I hope i can double post because i cant edit that message above.
I figured it out! No more humming. What i did is i plugged in the computer into the EQ and the EQ into the main reciever.
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