Hum tried DI Box with ground lift ,in line filters no joy

Filter capacitors in the amplifier or a broken ground (shield) wire. Check if there is a ground lift switch in your system and try it in both on and lift positions.

Check the connections to the cartridge. If you cannot locate an exterior source of the hum, it could be a fault in the power supply of the turntable, perhaps an Electrolytic Capacitor?

You are connecting a NOISY unbalnced line to a balanced input. Buy a DI box and then use an XLR to XLR to the mixer inout and run the MAC into the DI with "ground lifted". You will need to make a resistive mixer between the headphone jack and the DI as well. The headphone jack is STEREO. You COULD try a STEREO 1/8 inch splitter to 1/4 inch left and right cable... you MIGHT get away with that. Right now the left and right amps in the MAC are fighting eachother.

I ASSUME that you plugged your guitar into a DI box that then used BALANCED XLR cable to the Mackie board??? The guitar generates line level and the Mackie board inputs are mostly mic level... you will get distortion if you overdrive the Mackie board. You could try going into line level jacks, HOWEVER if you go any distance balanced interconnects must be used. Even the line level jacks require using TRS balanced cables. Try is using a DI box, and preferably one with a gain switch. Also fiddle with the ground lift switch on it for least noise or hum. I use the LiveWire brand DI boxes and they seem to work fine. Then it is important to set the gain with the trim on the MAckie so you don't clip. Also be aware that an acoustic guitar can "hear" speakers and you can get feedback or regeneration that will sound like you are in a cave.

How to isolate annoying background hum.

As long as the music or movie is playing, you can forget about it, at least until a quiet passage occurs, then there it is again: HUMMMMMMM! Be gone, bad hum, you think. But, like a bad odor at the back of the fridge, it takes some dogged persistence to track it down and eliminate it.

Hum is a constant low-frequency buzz, usually at about 60 Hz or 120 Hz, which results from voltage differences between true "ground" (what you'd get shoving a copper pipe into the ground) and the electrical "ground" of your receiver's chassis, the incoming cable-TV feed, or any video or audio components interconnected within your system, including powered subwoofers. When this voltage differential exists, it's called a "ground loop," and the hum it produces is darned annoying. You'll hear the hum mainly from the subwoofer because it's a low-frequency noise, but there will also be hum from your floorstanding front speakers or even compact bookshelf models.

First, try disconnecting your subwoofer from the coaxial sub cable from your AV receiver but leave the subwoofer turned on. Does the hum go away? If it does, then the ground loop is entering the system from your AV receiver and/or your cable-TV system set-top box (or satellite dish and decoder).

Disconnect the incoming TV-cable or satellite feed to a set-top box or to your TV and the A/V receiver. If the hum disappears (and you don't use a satellite dish) complain to the cable-TV company. They may know what you need and supply you with a ground-isolating transformer. If they don't know what you are talking about you'll need to order a video ground isolator and install it in-line with the TV cable before it enters your set-top cable-TV box. Axiom has special wide-band isolation transformers that will not interfere with any digital TV or HDTV signal. (N.B. You CANNOT use one of these with a satellite decoder box.)

Before you order one, you can try plugging your subwoofer into a different AC outlet in the room, ideally one that is not on the same circuit as your AV receiver and video equipment (TV, DVD player, sat or cable TV box, etc.) That may solve the problem. If it doesn't, see if the back panel of your sub has a "ground-lift screw". It will be labeled as such. Just remove it. That may remove the hum. If it doesn't and you have a standard cable-TV feed (not a dish), then order the ground-isolation transformer. (Axiom has special wide-band isolation transformers that will not interfere with any digital TV or HDTV signal.)
Axiom Audio Ground Isolator

If that still doesn't eliminate the hum, or if you use a satellite dish video feed, then you could try one of these from Radio Shack, which goes between the subwoofer and the coaxial cable from the receiver's subwoofer output.

With persistence, all ground-loop problems can be solved.

Hope it helped..

Have a nice day...

How to Eliminate the Hum and Buzz from your Sound System

Is your sound system making noises you don't want to hear? Try these tips to clear it up!

Instructions


Hum is usually the result of using electrical outlets with different grounds. To verify this, run an extension cord from the outlet that the amplifiers are plugged in, to the mixer.

Remove all the DI boxes and adapters. Connect the mixer to the amplifiers with balanced cables.

Be sure that all your cables and connectors are correctly wired:

Pin 1 shield
Pin 2 + white/red
Pin 3 - black

Note: If the system has an electronic crossover, equalizer, or limiter....you need to keep them in the signal chain to protect the system from damage. Just make sure all the cables are balanced and the pin-out on the connectors is correct.

If your gear doesn't have balanced connections use good shielded cables with the proper connectors.... NO ADAPTORS!!!


If the system still has noise, check each channel on the mixer by removing the input connections. There may be a DI box on stage that is also interacting and causing a ground loop. If that is the case try a different DI and make sure that all the instruments and amps on stage are also on the same dedicated ground as the mixer and amplifiers.


If the hum is gone using the extension cord you will need the have your electrician run a dedicated ground to the mixer and amplifier electrical plugs.

Simple Static Eliminationarcalian.com
Is static causing problems in your reel-to-reel (web) process?



Tips & Warnings

*
Removing the DI boxes, hum eliminators and bad cables may improve the sound quality...unless the DI boxes use very expensive line level transformers (Good ones are about $75 for just the raw transformer inside the box) the signal is being squished thru a $5 instrument level DI box.
*
DO NOT lift the grounds on any of the AC inputs to the amps or the mixer as this could result in electrocution. OUCH!


Hope it helped..

Please don't forget to rate me ..Thanks...

Have a nice day..

Hi, The Ground Rules Of all the annoyances that can afflict any audio/video home theater or even a simple stereo installation, the notorious "ground loop" may well be the most difficult and persistent one to track down and eliminate. A "ground loop" is caused by the difference in electrical potential at different grounding points in an audio/video system. (All the grounds in an A/V system should ideally be at "0" potential.) A ground loop typically adds a loud low-frequency hum or buzz as soon as you plug in any of various audio or video components, including subwoofers, cable-TV outboard boxes, satellite-TV feeds, TV displays, amplifiers, A/V receivers or turntables. The buzz/hum is a byproduct of the multiple power supply cables and a ground voltage differential within your system and its network of interconnecting cables.

Here are some methods to help you get rid of ground loops. Try these first and don't waste money on a power "conditioner" which, in most cases, won't help. (There is no need to "condition" the AC power for your system. Your receiver or amplifier already has a power supply with its own filters and transformers. No further filtering is normally required.)

If you get your system up and running and hear an audible buzz or hum, the first culprit to look at is either the powered subwoofer or your cable-TV or satellite-box feed at the entry point to your system.

First, the subwoofer: unplug the coaxial cable that connects to your powered subwoofer to see if the ground-loop hum disappears. If it does, it's likely coming in through your cable/satellite TV feed.

Reconnect your subwoofer's coaxial cable from the subwoofer input to your receiver's subwoofer output and disconnect the cable-TV feed (or satellite feed) from your outboard set-top cable box or satellite tuner. Be sure and disconnect the cable before any splitters. Now see if the hum/buzz from your subwoofer stops.

If that eliminates the hum, you can install one of these inexpensive in-line ground isolators from Parts Express or Bass Home. Note that these transformer-based ground isolators will work fine with analog cable-TV feeds, but depending on their design they may interfere with or block reception of HDTV signals via a digital cable or satellite dish feed.

Install the ground isolator between the cable-TV feed and the input of your outboard cable-TV box or satellite tuner (or the TV display's antenna or cable input if you have a set with a built-in TV tuner or a cable-card ready set). In many cases, the ground isolator will "break" the loop and remove the annoying hum or buzz by isolating the TV-cable ground.

If a hum remains with the TV cable completely disconnected from your system, or you don't want to risk degrading reception of HD signals from a cable or satellite system, then you may have to add a ground isolator like this Radio Shack Model 270-054 between the line-level coaxial subwoofer cable from your A/V receiver and the line-level input jack on your powered subwoofer.

In all cases, if your subwoofer has a ground-lift screw like some of Axiom's subwoofers, try first removing the screw (or replacing it) to see if it increases or eliminates the hum. It may or may not make a difference.

If you do not have easy access to the aforementioned ground isolators, here are a few more tips:

Try plugging the subwoofer into a different AC outlet in the room, one that isn't supplying power to your components (A/V receiver, TV, cable box, etc.). That might fix it.

Try reversing the AC plug for your A/V receiver or the powered subwoofer. If it's a 3-wire plug or a polarized plug, which has one prong wider than the other, you won't be able to reverse the plug. For safety, do not use a "cheater plug" to bypass the 3-wire plug.

With the power OFF, reverse the AC plugs one by one of any other components that have a standard 2-prong AC plug that isn't polarized. Each time you reverse a plug, turn on the system with the attached component and your subwoofer and see if the hum disappears. In some cases, reversing one or more plugs will eliminate the hum.

If you have a turntable, try connecting a separate ground wire to a chassis screw on your preamp or receiver and see if the hum disappears. If you already have a turntable ground wire, try removing it from the preamp. One or the other may eliminate the hum.

Finally, here is another solution that worked well for a member of our message boards who decided to discard his ground-loop isolator on his subwoofer: "I took off the ground-loop isolator I'd been using and connected a plain 14-gauge wire to chassis screws on the sub and the receiver then powered everything on. Although hum was still there, it was far lower than before. Next I unscrewed the ground-loop screw on the back of the sub and that took care of the hum completely."

Almost certainly sounds like an earth loop to me, but can be caused by a poorly made transformer or phase shifts on the mains supply. Visit some power conditioner web-sites like Isotek or Isol-8 (or google "earth loop") where there's plenty of advice on how to reduce/eliminate earth loops and other causes of mains-induced hum (transformer problems etc).

Hum on the speakers usually indicates that there is a DC voltage on the speaker line. DC voltage on the output lines would be caused by a shorted output transistor.


Have a nice day...

The probable cause is a ground loop. You haven't said what you are plugging in. These inputs are BALANCED lines and you MUST use TRS cables driven by TRS outputs of the thing you are driving it with. ALL interconnected equipment MUST be powered by the same receptacle or power source.
IF the thing you are driving it with does not have balanced outputs, then procure a DI (Direct Input) box and use an XLR cablle between the DI and the Alpha and set the DI on ground lift.

What you have sounds a lot like hum-bars and is caused by different ground potentials. Is the Sat box grounded? Try lifting the ground using a ground cheater, or use a ground breaker on the incoming Coax line from the dish.

Sometimes it can take quite a bit of playing around with.

I hope this helps

Thanks