Harmony Central Forums
Announcement Announcement Module
Collapse
No announcement yet.

Electrical Noise

Page Title Module
Move Remove Collapse









X
Conversation Detail Module
Collapse
  • Time
  • Show
Clear All
new posts

  • Electrical Noise

    One of the venues we play quite often has an intermittent noise issue coming from the house electrical system. I'm sure it's not our gear, we only hear this problem when we play this particular venue and another band that was just finishing told us they had the same issue. I've been doing this for quite some time and it's the first time I've heard anything like this. It only seems to affect the PA, we hear bursts of noise through the fronts and monitors lasting from a split second to sometimes 5 or 6 seconds. The bursts seem to be completely intermittent ranging from 5 to 20 minutes apart. I could best describe it as a crackling buzz? The stage, (it's a small outdoor venue), has it's own sub panel with a dedicated 20A GFI quad outlet. I chased around the facility trying various different outlets and it made no difference so I suspect it is system wide issue. At first I through maybe it was a pump or motor but the more I thought about it I think it's some kind of arcing issue in their electrical system.

    Our system is a Mackie Onyx 1620 board feeding four RCF 312's with a graphic EQ for the monitors and and old midiverb for effects. I always power the entire PA system from a single 120V source to prevent any loop issues. My thinking to resolve the issue on our end is to use a UPS system as a line conditioner on at least the rack and mixer, (I know the electrical noise isn't directly affecting the cabs). Does any one have experience with this? Any issues or problems I might not foresee?

    Thanks.
    Last edited by IanHey; 08-18-2014, 12:55 PM.

  • #2
    Have you ruled out any outside sources such as RF being induced into something by a high powered data transmission that is often used in commercial or municipal utilities? This can enter through wireless receivers as broadband noise, but can also enter through other means such as mic lines, guitar amps, etc.

    It may or may not be related to the power source, these are hard problems to chase down.

    Could also be signal impressed on the power system from a VFD (variable frequency drive), are there any large pumps nearby? These VFD's (can) operate at fairly high frequency (when harmonics are considered) and the currents can be high enough to induce noise into the system
    Last edited by agedhorse; 08-18-2014, 02:55 PM.
    -------------------------------------------------------------------------------------------------------------------------------------------------------------------
    Former product development engineer: Genz Benz, a KMC Music/Fender Musical Instruments Company, continuing factory level product support and service for Genz Benz

    Currently product development engineer: Mesa Boogie

    Comment


    • #3
      Originally posted by agedhorse View Post
      Have you ruled out any outside sources such as RF being induced into something by a high powered data transmission that is often used in commercial or municipal utilities? This can enter through wireless receivers as broadband noise, but can also enter through other means such as mic lines, guitar amps, etc.

      It may or may not be related to the power source, these are hard problems to chase down.

      Could also be signal impressed on the power system from a VFD (variable frequency drive), are there any large pumps nearby? These VFD's (can) operate at fairly high frequency (when harmonics are considered) and the currents can be high enough to induce noise into the system

      I thought about RF. We don't use anything wireless. I thought if it was RF I would hear something in the back line ... which I haven't. I pulled down the faders individually trying to isolate to a single mic / cable and it didn't seem to matter, just the main faders killed it. That said, it's impossible for me to rule it out but my hunch is that it's an electrical problem. As far as a drive making the noise, I looked around and all I could see were small wall / window mount AC units. The venue location is in the middle of a canyon, they have about 6 small buildings. Their business is selling bottles of wine and letting people enjoy it on their property, so there's not too much going on.

      We've used this set up for over 60 different venues at least and haven't had any issues like this anywhere else.
      Last edited by IanHey; 08-18-2014, 03:57 PM.

      Comment


      • #4
        If the noise goes away with the main fader down, it could be something entering the summing bus (a particularly vulnerable access point into the signal path... a soft white underbelly) or by any chance do you have something inserted in the main insert loop (if the mixer has one)?

        Normally, I wouldn't expect the noise to go away with the fader down if the source of the noise was through the power source. Possible, but unlikely.
        -------------------------------------------------------------------------------------------------------------------------------------------------------------------
        Former product development engineer: Genz Benz, a KMC Music/Fender Musical Instruments Company, continuing factory level product support and service for Genz Benz

        Currently product development engineer: Mesa Boogie

        Comment


        • #5
          Originally posted by agedhorse View Post
          If the noise goes away with the main fader down, it could be something entering the summing bus (a particularly vulnerable access point into the signal path... a soft white underbelly) or by any chance do you have something inserted in the main insert loop (if the mixer has one)?

          Normally, I wouldn't expect the noise to go away with the fader down if the source of the noise was through the power source. Possible, but unlikely.

          The system is a very simple set up. Mics in, mains out, aux 1 to monitors via EQ, aux 2 to midiverb and return for effects. The power supplies are all built in except for the midiverb wall-wart. The noise definitely followed the faders. Every time we play this venue we get this issue and it's the only place we get it and as I mentioned the band before us said they had similar issues.

          Comment


          • #6
            Something connected to the system is the culprit. The "tell" is the issue is gone with the main level down.

            You are running fully balanced correct? Tube amps, connections that are not balanced check.

            Run the system with nothing terminated to the mix. You have a process of elimination.

            Comment


            • #7
              Originally posted by Pro Sound Guy View Post
              Something connected to the system is the culprit. The "tell" is the issue is gone with the main level down.

              You are running fully balanced correct? Tube amps, connections that are not balanced check.

              Run the system with nothing terminated to the mix. You have a process of elimination.

              Everything is balanced. Why would the band before us have the same issue with their gear if it was an issue with my rig and why is this the only venue out of more than 60 that the issue occurs? In my mind the only common denominator is house power or some kind of RF that only occurs at this venue.
              Last edited by IanHey; 08-18-2014, 06:19 PM.

              Comment


              • #8
                Your equipment isn't the only equipment that might be open to noise intrusion. If it's in the area, RF has many opportunities to enter the system via outside sources such as guitar amps, bass amps, bad mic lines etc. All of these thigs can be present in other systems as well as yours.
                -------------------------------------------------------------------------------------------------------------------------------------------------------------------
                Former product development engineer: Genz Benz, a KMC Music/Fender Musical Instruments Company, continuing factory level product support and service for Genz Benz

                Currently product development engineer: Mesa Boogie

                Comment


                • #9
                  Originally posted by agedhorse View Post
                  Your equipment isn't the only equipment that might be open to noise intrusion. If it's in the area, RF has many opportunities to enter the system via outside sources such as guitar amps, bass amps, bad mic lines etc. All of these thigs can be present in other systems as well as yours.

                  Which is why I haven't completely discounted the probability of RF being the issue. That said, I don't have all day to spend at the location trying to resolve the issue which is why I am thinking about putting a UPS in front of the mixer / rack to see if that resolves the issues. If it does fine, if not I'm probably looking at an RF issue that I wound't know where to start trying to resolve ... probably here?

                  Comment


                  • #10
                    Rf interference can come from many things ... Fluorescent or LED lighting, motors for fans, any digital equipment, video monitors, cell phones and iPads. Troubleshooting starts at the end of the chain and after you prove out each piece you move one cable and then one piece of gear forward until you find where the problem is getting into the system
                    Don Boomer

                    Comment


                    • #11

                      Originally posted by IanHey View Post
                      ... It only seems to affect the PA, we hear bursts of noise through the fronts and monitors lasting from a split second to sometimes 5 or 6 seconds. The bursts seem to be completely intermittent ranging from 5 to 20 minutes apart. I could best describe it as a crackling buzz? ...
                      Can you give more details about the venue building, the physical location (city, on a mountain, near any military bases, etc) and whether the building is shared space with any other buildings? Any banks close by?

                      What you describe sounds like microwave transmission bursts. Security systems use it, and there are communication systems that use microwave, but you'd need to be very close to the line of sight that the beam is sent, or some part of the local electrical system would be.

                      Your idea of a UPS is good, but it would need to be a battery/inverter system, not cheap.
                      Last edited by Craig Vecchione; 08-19-2014, 05:56 AM.
                      .....

                      Comment


                      • #12
                        Originally posted by dboomer View Post
                        Rf interference can come from many things ... Fluorescent or LED lighting, motors for fans, any digital equipment, video monitors, cell phones and iPads. Troubleshooting starts at the end of the chain and after you prove out each piece you move one cable and then one piece of gear forward until you find where the problem is getting into the system

                        I actually have a fair amount of experience over the years troubleshooting power, lighting and low voltage systems. I have isolated the issue to the mixer or the midiverb unit. There is nothing in the back line. It can't be the mains or the monitors. I shut off the mics etc. and I still had the problem until I cut the mains. I thought about lighting but this was happening during bright day light.

                        Comment


                        • #13
                          Originally posted by Craig Vecchione View Post


                          Can you give more details about the venue building, the physical location (city, on a mountain, near any military bases, etc) and whether the building is shared space with any other buildings? Any banks close by?

                          What you describe sounds like microwave transmission bursts. Security systems use it, and there are communication systems that use microwave, but you'd need to be very close to the line of sight that the beam is sent, or some part of the local electrical system would be.

                          Your idea of a UPS is good, but it would need to be a battery/inverter system, not cheap.

                          It's in a canyon in the Malibu hills, not much else around within a mile or so. The area is 10 miles from anything built up. The site has about 6 buildings on it that are more or less shacks. They do have coolers and AC units and I'm sure they have some kind of broadband. As far as military bases, microwave, cell sites etc. I don't think so but I wouldn't be surprised. I do know of one comm facility that I have worked at in those hills but that has to be 10 miles away at least.

                          Comment


                          • #14
                            That area is full of microwave and rf traffic, much of it VERY high powered.
                            -------------------------------------------------------------------------------------------------------------------------------------------------------------------
                            Former product development engineer: Genz Benz, a KMC Music/Fender Musical Instruments Company, continuing factory level product support and service for Genz Benz

                            Currently product development engineer: Mesa Boogie

                            Comment


                            • #15
                              Funny, I live about 6 miles the other direction from there (Pt. Magu Naval air station). One day last year all the garage doors in our condo association all of a sudden opened and were unresponsive to each homeowner's controls. Then just like that, but 3 days later, that all mysteriously started working again. The military can pretty much do whatever they want RF wise without letting anyone know about it.

                              My best guess to your problem is a motor starting up in a cooler or air conditioner. However where it is entering your system could be anywhere ... through the air or through the AC.
                              Last edited by dboomer; 08-19-2014, 11:54 AM.
                              Don Boomer

                              Comment



                              Working...
                              X