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Roland AC-33 Buzzing loads line out headphone out into PC?

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  • #16
    Where's the buzz/usb interface thread?

    I've tried establishing why there's a ground loop but to no avail.
    I'd love to deal with/fix the source of the problem.
    I don't know what that is though.
    I have two electrical components producing a ground loop when I connect them,
    that's the source of the problem.
    Apparently it's a common problem.

    Roland recommend this:
    ttps://www.bax-shop.co.uk/miscellaneous-peripherals/art-dti-ground-loop-isolator?gclid=EAIaIQobChMI9Km88quO1gIVYbHtCh2D8AC pEAQYAiABEgIvE_D_BwE

    I haven't got another 50 knocking around.

    Why doesn't everyone experience this when connecting two electrical things on the same circuit?

    Is it the wiring in the property?

    Comment


    • #17
      Originally posted by ilikepetedotcom View Post
      Where's the buzz/usb interface thread?
      http://www.harmonycentral.com/forum/...-weird-problem

      That was a different situation from yours (every setup is different) and in that case, the user was able to determine, by substitution, that he had a buzz with one synthesizer but not with the other. That helped to narrow down the problem and he solved it by lifting the ground pin of the power plug for the buzzing synthesizer.

      If I'm remembering this correctly, when the line or headphone output of the amplifier is connected to the line input of the computer, the amplifier buzzes when it's operating from its AC power supply, but doesn't buzz when the power supply is unplugged and it's running on its batteries. One clue (if I remember this correctly) is that it doesn't matter whether you have something plugged into the amplifier input or not.

      So this suggests that the problem is with the amplifier's power supply. Maybe you can work around this, but you can't really fix it. Maybe Roland can, but probably not, since they suggested that you try a ground isolator. That's just what I suggested a few posts back. The lowest cost one that I know of that does what it's supposed to do is this one (again):
      https://www.radioshack.com/products/...-loop-isolator It's only $10


      Why doesn't everyone experience this when connecting two electrical things on the same circuit?
      Because sometimes everything is right the first time. Yiou can eliminate the house wiring as a problem by plugging everything you're connecting together into a single outlet strip. I think you've done that. If there's a ground pin on the plug for the AC power adapter, try using a ground lifter (3-to-2-wire adapter). Those only cost a dollar. Or try the analog line isolator. Or go back to Roland with a clear description of the problem and what you're tried in order to troubleshoot it. Tell them that it points to the amplifier when it's running on AC power, and suggest that they send you a replacement power supply to try. Maybe they'll cooperate.

      It just might not work without modifying the amplifier. It's your choice, then, whether to get it fixed right or return it and try a different amplifier.

      --
      "Today's production equipment is IT-based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio." - John Watkinson, Resolution Magazine, October 2006
      Drop by http://mikeriversaudio.wordpress.com now and then

      Comment


      • #18
        Hiya,
        I can't find your USB interface reply? In another thread?

        "but a better solution would be to find out why there's a ground loop and then fix what's broken (or was never built right)"

        I've been trying to find out my problem,

        That's what I'm here for Mike

        I have a ground loop... Established..

        Roland told me that too.. Recommended a £50 thingy box..
        Kinda matter of factly, Yeah, our amps buzz when you connect them to other devices. We know that, Chuck another 50 at it..

        Then added it's my recording device not grounded properly, feeding into the grounded properly Roland!
        My recording device is powered/grounded in exactly the same way as the Roland!
        Why is theirs the automatic king of the ground?

        I asked, If they know their amps are contenders for ground looping, why not install the little boxes in the amps to start with, coasting pennies probably.. Roland designed to ensure the consistency of their precious sound as external ones by all accounts lose bottom end quite drastically.

        I asked them how to fix the source of my looping ground. What's in the Roland making it loop that is not present in other devices that don't produce a loop.. I hope they explain.

        Guess that's my new question..

        How to fix a ground loop at source without adding audio isolators further down the line to paper over the cracks?

        Does the house need rewiring?

        In what conditions would I electrocute myself 'lifting the ground'?
        Don't play in the bath or?
        My reasoning is I've used this ungrounded adapter in spain. I didn't blow up..
        Hmmm?

        Comment


        • #19
          Originally posted by ilikepetedotcom View Post
          Hiya,
          I can't find your USB interface reply? In another thread?
          It's the last post in the link I posted. It doesn't apply directly to your situation, but it's just another example of a problem with one piece of equipment that doesn't show up when used one way becomes a problem when used in another way.

          I've been trying to find out my problem,
          That's what I'm here for Mike
          I have a ground loop... Established..
          I understand that, but there's only so much troubleshooting by message that one can do. You probably have a ground loop, but "ground loop" is a general term that gets thrown in every time someone has a hum or buzz problem. But there's no unique solution, and, always, the best way to solve the problem is not by disconnecting wires or inserting transformers, it's to locate the damn problem and fix it - which can sometimes involve modifying the device that's causing the problem. But I don't think you're going to do that, and neither is Roland.

          I'm surprised that Roland gave you the answer that they did - that they were aware that the amplifier can hum when connected to other equipment. I'm not surprised that they suggested adding the ground isolator. It's a pretty good band-aid and works more often than it doesnt.

          Then added it's my recording device not grounded properly, feeding into the grounded properly Roland!
          My recording device is powered/grounded in exactly the same way as the Roland!
          Why is theirs the automatic king of the ground?
          Actually, the problem could be with your computer. Did you say you tried a different computer, or was that the other discussion here about a hum problem? Have you tried feeding the output of the amplifier to some other piece of equipment that isn't your computer, or isn't connected to your computer? Maybe to another amplifier, or a home stereo system? The idea is to try enough combinations of the pieces in some other configuration than you're using them in, for the purpose of determining the real culprit. No point in trying to fix your amplifier if it's really the computer that's at fault. Sometimes troubleshooting requires substitution, and in order to do that, you need things you can substitute. This just may be beyond your resources right now.

          I asked, If they know their amps are contenders for ground looping, why not install the little boxes in the amps to start with, coasting pennies probably.. Roland designed to ensure the consistency of their precious sound as external ones by all accounts lose bottom end quite drastically.
          I wrote an article about this sort of problem in Pro Audio Review about 10 years ago. I tested a few different ground isolators, and found that the Radio Shack one was actually pretty good as long as you don't try to run it at too high a level. The Ebtec, which is about on par with the one Roland recommended, had considerable distortion down around 30 Hz, but that's probably below the range that the speaker in the amplifier can reproduce anyway.

          I asked them how to fix the source of my looping ground. What's in the Roland making it loop that is not present in other devices that don't produce a loop.. I hope they explain.
          Oh, I'm sure they won't explain. One thing is that the outputs aren't balanced. This saves a little money but denies you the abilty to break a ground loop right at the output. Putting a transformer in between the amplifier and the computer balances the output and separates the computer ground from the amplifier ground.

          Guess that's my new question..
          How to fix a ground loop at source without adding audio isolators further down the line to paper over the cracks?
          Does the house need rewiring?
          The house doesn't need rewiring. At least not until you eliminate every other possibility, which you haven't, yet. The way to fix a ground loop problem is to be sure that the all of the grounds that go to the outside world are at the same potential. This is first a function of good design practice, and second, building it to accomplish what has been designed. Sometimes the sleeve of a TRS jack goes through a fairly long conducting path before it joins up with the power supply ground and the ground that goes to the power plug, if any. Sometimes you can fix a problem like this by connecting a heavy gauge wire between the sleeve terminal of the output jack and the power supply ground point. But I can't tell you how to do that on an amplifier that I've never seen, and Roland won't tell you either because their lawyers don't want you messing around inside their gear.


          In what conditions would I electrocute myself 'lifting the ground'?
          Don't play in the bath or?
          My reasoning is I've used this ungrounded adapter in spain. I didn't blow up..
          Hmmm?
          In Europe, at least in some countries, and I don't know if spain is one of them, neither side of the AC power line is connected to ground. In the US, it is. To avoid typing it again, I'll quote myself here from that post I sent you to that you couldn't find:

          Originally posted by me
          I was hesitant to suggest that you try lifting a power ground, because that's a safety thing. It's sometimes a good diagnostic tool, though, to show you what device is causing the problem.

          The reason why there's a ground pin on the power plug is that inside, it's connected to the chassis. (sorry if you already know all this) The idea is that if the hot side of the power line somehow shorts to the chassis, rather than letting you complete the current path by touching the chassis while you're standing on something that's grounded, insted it immediately short circuits the hot side of the line to the low (ground) side and blows a fuse before you, rather than the fuse, gets electrocuted.
          --
          "Today's production equipment is IT-based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio." - John Watkinson, Resolution Magazine, October 2006
          Drop by http://mikeriversaudio.wordpress.com now and then

          Comment


          • #20
            ok, cheers Mike, read and understood!
            Thanks..
            Really, thanks so much for your time,
            it has brought light and sense to my darkness..
            I hope you type faster than I

            Here is todays reply from Roland,
            A bit more in depth so I thought it may be of interest.


            'The majority of laptops are not earthed ( infect I do not know a single one that is.)

            It is a right pain dealing with grounding problems – many people using laptops with audio interfaces connected to studio monitors that are earthed get the same issue.
            This is just part and parcel of connectivity.

            Our amps do not buzz. – What you are hearing is the other devices ground hum coming through the speakers.
            Also connecting from a built in sound card through non shielded cable is not the best option also. ( but I have done so a few times )

            The reason many laptops are not earthed is because of space on the laptop. As you can see, you just have a positive ( centre pin ) and negative ( outer ) to connect power to on your laptop. – If it were earthed , you would need three “Connections”. – Plus as far as health and safety, laptops do not need to be earthed.

            Audio isolators actually cut 50hz buzz from the audio signal – the mains frequency, so there is ever so slightly tonal differences.
            But if maximum audio quality were top priority, you should be recording into an Audio Interface that offers the best connectivity, shielding and inputs.

            Majority of laptop inputs have preamps enabled on them, for mic inputs etc that add to the issue.

            Also try disconnecting the laptop from power while recording, the noise may reduce.

            All our audio interfaces have shielded AD/DA components, ground loop switches built in etc because this is the area where people will run into problems..'



            Comment


            • #21
              AHA! There's my original reply up there!!
              I didn't see it yesterday so wrote again! That explains that then.

              Roland guy says laptops aren't grounded..?
              I'm guessing the transformer is grounded though?
              Otherwise I could lift the ground from laptop instead and operate safely? Or?

              I'm assuming my ungrounded 3pin - 2 pin travel adapter does the same job as the dollar ground lift device from radio shack?

              and yes, the buzz has gone if I use it on the amp or the laptop supply..

              in which case, does this cancel the electrocution risk?

              Because that's cured my buzzing!

              Comment


              • #22
                Originally posted by ilikepetedotcom View Post
                Roland guy says laptops aren't grounded..?
                I'm guessing the transformer is grounded though?
                Otherwise I could lift the ground from laptop instead and operate safely? Or?
                That answer from Roland is kind of convoluted, but the principle is there. It's not that one device is sending hum to the other device, but rather, that the connection between the two causes hum to enter the system (the system being the amplifier, the computer, the audio cable between them, and the power cords for both the computer and the amplifier.

                I've never been fully clear as to whether your "computer" is a laptop (with an external power supply and batteries) or a desktop (with a standard AC wall plug, so I tried to avoid the details. So which are you using? Or have you tried both? And, about when running on batteries - I'm pretty sure you said that the hum goes away when you unplug the amplifier and run it on batteries. If you're using a laptop, does the hum also go away if you unplug the laptop and run it on batteries (with the amplifier running on AC)? If either one of those cases is true, and I'm sure at least one is since you said the hum went away when running on batteries (but it wasn't clear what was running on batteries), then you've eliminated the hum be breaking the connection between the two that's made through the power line ground - which is what you do when you use your back-to-back adapters to un-ground whatever it is that you're plugging in through them.

                I'm assuming my ungrounded 3pin - 2 pin travel adapter does the same job as the dollar ground lift device from radio shack?
                Well, yes, it does the same job, but it does it in a different way. The ground isolator leaves both the computer and the amplifer grounds connected together through the AC power plug and disconnects the ground connection between them that goes through the audio cable shield. The "ground loop" is that you have two ground paths between the amplifier and the comupter that aren't exactly at the same electrical potential due to leakage and other things that make theory and practcie different. Any way that you can break that loop will usually solve the problem.

                Here's a funky sketch showing the ground loop path traced in red. Lifting the ground pin on either power supply or putting the isolator in the audio cable, which breaks the shield, will break the loop. You can sometimes fix the problem by disconnecting the cable shield at one end. This allows the ground connection through the power plugs to complete the path for the audio signal, but you'll get no audio (and probably a lot of hum) if you unplug either the computer or amplifier and run it on batteries.

                Click image for larger version

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                In reality, you probably won't get electrocuted because there's not much in the way of grounded metal that you can touch. But the chassis can become "hot" if the hot side of the power line shorts to the chassis. Since there's a transformer in the power supplies, that isolates the power supply (which is in a plastic case anyway) from the power line so the hot side of the AC line can never get to the amplifier chassis.

                The Roland guy did make a good point about the mic preamp at the computer input. There's a lot of gain there, and, being an unbalanced input, even though the cable is shielded, it's susceptible to picking up hum just from electrical things nearby. A line level input, which some desktop computers, but practically no laptop computers have, has lower gain and are less sensitive to hum being picked up by the audio cable.

                Also, he said that the ground isolators cut 50 Hz (the line frequency) and affect the tone. He's thinking it acts like a filter. If that's how it worked, he'd be admitting that the hum is coming from the amplifier. It doesn't work that way, though. Low frequency response isn't as good as a straight wire, but among the isolators I tested for my article, they were all pretty flat down to about 30 Hz. You will get an increase in low frequency distortion with an isolator (less with the better ones) sometimes what it adds can be kind of pleasant.


                --
                "Today's production equipment is IT-based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio." - John Watkinson, Resolution Magazine, October 2006
                Drop by http://mikeriversaudio.wordpress.com now and then

                Comment













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