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egervari
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#1
19th February 2011
Old 19th February 2011
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Help fixing signal hum/mouse coming out of monitors?

Hi, I just some Truth B2031A monitors and connected them to my Edirol FA-66 sound card and I am noticing that I getting hum when no music or anything is playing through them. Besides that, they work great.

I did some research, and all of my finds on this forum, the online PDF manual and other places lead me to think it was because I was using unbalanced 1/4 cables. So I went out and got balanced TRS cables.

This unfortunately didn't solve the problem. So I did some more research and I might have something called a ground loop problem?

I get noises when I move my mouse wheel up and down, which I saw that some people were getting that problem due to using non-balanced cables.

I'll be honest - I don't know anything about this stuff, so I'd like to ask for some help.

I basically have everything on my desk - my lcd monitor, my computer chassis, and the 2 monitors on either side of the desk. My sound card sits on top of my computer chassis, which is sort of the middle.

All the power cords are hooked into the same power bar.

I know the FA-66 didn't cause hum before with my last set of monitors, so it's not the FA-66 directly, although it could be causing some kind of conflict with these monitors?

I read in the manual that the Truth's are supposed to be near-field monitors and it says they were designed to be placed next to the computer. Could that not be the case? I don't have anywhere else to put them.

What else should I try? The hum/noise is very annoying, and it's going to make it harder to detect real noise when I restore audio files :(

Thanks for the help.
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20th February 2011
Old 20th February 2011
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I did my best to really clean up the cables in the back, and it changed nothing.

I also moved the sound card off to the side. This also changed nothing.

When I turn my computer off, a large chunk of the noise/hum is gone. If I turn off my sound card, or simply remove the firewire cable out of it while the power on the sound card is on, the noise is virtually eliminated.

My guess is that my computer has to be the problem then, right? What do I need to do to fix this? :/

So much for Behringer saying these are near-field monitors that don't have this problem. They lie :(
#3
20th February 2011
Old 20th February 2011
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Hi there.

I had these problems as well. I think the only solution is to get isolation transformers. Though I haven't tried this myself, I live with it for now. The idea is you connect the output of whatever your setup is into the transformer before going into the input of the computer sound card. Also, the other way, put a transformer between the output of the computer to the input of your console/mixer. If you can afford it get the best quality you can because they will affect your entire sound. They are not expensive compared to the costs of high end gear.

If the computer has a ground loop problem that's going to be practically impossible to get rid of. So isolation transformers are your best bet.

Some other solutions:

1. Check your outlets for proper grounding.

2. Check your units one by one, isolating the problem. I found one of my preamps was faulty. Channel 2 was causing a ground loop.

3. Separate your power cables from the cables carrying audio signals.

4. Use plastic washers on your rack gear to isolate them more.

5. If these fail, time for isolation transformers.
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egervari
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20th February 2011
Old 20th February 2011
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Thank you very much for the response.

1. I am not sure about how to test if my outlets are properly grounded. If they were not properly grounded, would I have come across this issue at any point in the past? This is a new problem.

2. There are not many units to consider. The monitors do not hum or buzz when they are the only things that are powered.

When I turn on the sound card, I get some hum. If I unplug the firewire cable from the sound card while it's on, the hum is gone.

When I turn the computer on, the hum is very buzzy/annoying. It's not so loud, but it's not right either. It's distracting.

3. What do you mean by separating my power cables from the ones carrying the audio signals? I have 2 power cables plugged into the power bar that go to the monitors. 2 other power cables in the power bar go to the monitor and the power supply of the computer. Another plug goes to the sound card. 5 in total on the power bar.

The audio cables are plugged from the monitors to the sound card. They don't appear to be "touching" if that's what you mean. I have separated them already. Is that what you mean?

4. I don't have any rack gear. Besides the FA-66 sound card, that's all there is too it. I don't use any mixing board at all.

5. One I understand everything you've suggested, that might very well be the only option at this point :(
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20th February 2011
Old 20th February 2011
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It looks like this guy has the same problem:
Noise problem with firewire audio interface at DVinfo.net

No solution was found out on this forum though :( He's tried even more than I did, but I did many of the same things as him too. Sounds like the exact same problem. Pitty there is no solution :(
#6
20th February 2011
Old 20th February 2011
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I was reading about something similar the other day. Have you tried unplugging various USB cables to see if the sound goes away? Apparently they can be the source of ground loops sometimes.

You can cure them by finding the correct ground pin on the offending USB cable and simply covering it with paper to short the connection, thus eliminating the loop.

I'll see if I can dig up the thread.


Regards,

Warren
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20th February 2011
Old 20th February 2011
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20th February 2011
Old 20th February 2011
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Thanks for the link! I'll give that a read right away.

I just wanted to post back and say I tried disconnecting the USB devices. First, I thought maybe it was my external hard drive. That's not even connected now, but that didn't do it.

I just disconnected both my mouse and keyboard right now, as you suggested. It made no difference.

Of course, I disconnected the firewire cable from the back of the computer solves the problem. It does the same thing as disconnecting the power firewire cable from the sound card - it fixes the noise problem. Does this provide a link/solution?
#9
20th February 2011
Old 20th February 2011
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The link is geared around general ground loops and then focuses on the USB ground pin problem. Check it out.

Maybe there's a similar firewire solution?
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20th February 2011
Old 20th February 2011
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Yeah, I read everything in there... it didn't mention anything I didn't try. I think that person's issue is a lot simpler. He wasn't even using balanced cables or an external audio device :/ He didn't even mention what his monitors were. He just says speakers.

Anyway, the firewire cable is for the FA-66 audio hardware, so I can't remove it I tried using a different 6-pin -> 4-pin cable and I get the same problem.

On the back of my monitors, I have a -6 to +6 knob to control the "Input Trim". This doesn't get rid of the hum, but it does reduce it. I then boost the volume on the FA-66... and that doesn't increase the hum. For right now, does this sound like a temporary work-around? Or is it really bad to use this input trim on the monitors?

Does the above solution give any indication as to what is really the main problem?
#11
20th February 2011
Old 20th February 2011
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Using the trim on your monitors shouldn't hurt. It's just like turning down the gain settings on an amplifier. If it plays loud enough for you w/ the gain down that should be fine.

Are the monitors, computer and interface all plugged into the same circuit? Do you have a soldering iron?
#12
20th February 2011
Old 20th February 2011
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You have a ground loop. Try lifting the ground pin (power cord) of your monitor (visual LCD etc.) and then also the ground to the CPU using a 3-2 power adapter (at least here in the US). Then you can at least find where the ground loop is. You might have to plug everything connected to your computer and the audio interface into the same power strip to get it to go away.

Grounding scheme's in computers are piss poor when it comes to audio. Noisy power supplies and wall warts/line lumps for monitors and silly things like USB hubs can wreak havoc on you grounding.

good luck,
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20th February 2011
Old 20th February 2011
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Thanks for the response Ashley

Everything is already using the same power bar (or strip if that's the same thing).

As for "lifting" the ground pin, what do you mean? Do you mean making sure it's not touching the floor? If that's the case, it's already lifted I guess.

I didn't know what a 3/2 Power Adapter was, but all of my outlets in the wall and on the power bar are already 3 pronged. All the power cables have 3-prongs as well, including the power bar itself. How would this solve the problem? (I'm not sure, because I don't know how this stuff works).
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20th February 2011
Old 20th February 2011
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Oh, I want to add something, since I've been reading about what lifting the ground pin means (sorry, I'm an idiot, but I'm learning!).

I found a website that talks about doing this, and it says that it's unsafe and to use an isolation transformer instead.

Anyway, the thing I wanted to add is that this hum is not a 50hz or 60hz hum. It is a high pitch whine. If I disable the tweeter on the monitors, it basically goes away completely. Does this still sound like a ground loop? The reason I mention this is that the ground loop should cause the 50-60hz hum, no? Or will it cause both but I can't hear the 50-60hz?
#15
20th February 2011
Old 20th February 2011
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He's suggesting using a 'cheater plug' on the plug that lifts the ground from connecting to the outlet. By 'lift' it means disconnect.

I asked if you had a soldering iron 'cause you could try another method as outlined in the excellent document below.

See suggestion #8 for TRS to TRS balanced connections.

Sound System Interconnection
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#16
20th February 2011
Old 20th February 2011
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Oh, I don't have a soldering iron, but I could probably get one or ask someone to help me to do something with it. Let me read that article you posted.
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20th February 2011
Old 20th February 2011
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High pitched whine sounds like something else altogether. Forget my idea, either you were not hearing this sound before due to bad speakers or the monitors are messed up perhaps.

Hi whine is not a good thing. Hum is normal and has many ways of being dealt with but whine.....tutt not so good.

-ashley
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20th February 2011
Old 20th February 2011
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Maybe whine isn't the best way to describe it. It's a hiss maybe? I don't know. It's not a low sound at all. It's low-volume, but it's also piercing and can give a headache if I listen to it too long.

The reason I don't think it's due to the monitors is because if the computer is not turned on, this hiss/buzz is not present in the monitors - like if I had the monitors turned on but the computer off. The hiss only occurs when the computer is turned on.

Of course, the FA-66 causes some of it too. If I turn off the FA-66 and the computer, all of it is gone.
#19
20th February 2011
Old 20th February 2011
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I have a similar problem and have just spent some time trying to troubleshoot it (instead of working on some music, sigh).

Here's the setup:

* External mixing desk master audio out -> ESI ESU 1808 audio interface in
* Audio interface USB -> PC USB
* All power cables connected to the same power strip
* Headphones plugged into mixer's phone output with volume at 0

I now hear VERY noticeable whining/crackling in the headphones, and the crackling is affected by mouse movement, scrolling windows, hard drive activity etc. I can basically hear the computer do its stuff through the headphones. This despite the fact that the headphones are not connected to any PC audio output at all. The noise seems to be travelling backwards through the cable that feeds audio out from the mixer to the audio interface input.

So I tried the following:

* disconnected audio cable from mixer -> audio interface: noise stops
* disconnected USB cable from audio interface -> PC: noise stops
* turned PC off: noise stops
* pulled audio RCA cable halfway out of audio interface so that the outer metal rings did not touch: noise stops in headphones, but noisy signal still goes into the audio interface through the center pin
* tried a different USB cable: noise remained

When I turn the PC on, the noise starts the instant it is switched on, I can hear the hard drives spinning up etc in the headphones.

Then I got the laptop out, and connected the USB cable from the ESI audio interface to the laptop. Voila, no noise! However, as soon as I plug the laptop power cable into the wall, I get the exact same noise from the laptop. I tried several different wall sockets and I get noise with each one.

The only conclusion I can draw is that there is nothing wrong with either my PC or my audio interface, but that there is some weird power-related cause. Does this seem like a ground loop? As mentioned above, the noise I hear is not a low-frequency hum, so I was unsure whether it really was a ground loop.

And if so, is the only solution one of those isolation thingies? I have zero experience with electronics so things like "lifting the ground" scares me a bit. But maybe I can give the paper USB solution a shot.
#20
20th February 2011
Old 20th February 2011
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Actually no, covering USB pin 4 with a bit of tape did not fix the problem.
#21
20th February 2011
Old 20th February 2011
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if we plug out of the spkr/headphone mini on the front of our mac we get low level digital noise in the spkrs.... if we plug into the rear jack all the noise goes away.

do you have anothr spkr jack to work with?
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#22
20th February 2011
Old 20th February 2011
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I had a similar problem with mouse noise coming out of my monitors (alesis point seven).

The thing that stopped it on my system was to go into the pc's audio mixer (double clicking on the speaker icon) and turning off 'PC Beep'.

You might not see it when you first open it up, but go into 'options/properties' and you will see a series of check boxes. Find the one that says 'PC Beeps' and check that box. It will show up in the mixer then. In the mixer put a check in the 'mute' check box for PC Beep.

Once I did that I didn't have any mouse sounds in my monitors.
#23
20th February 2011
Old 20th February 2011
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You DO have a ground loop. The only way to eliminate it without safety issues or having to buy iso trannies is to lift the ground on the audio cables going to your monitors ("star grounding")

Assuming they're XLR, unscrew the male plug going into your monitors, finding the shield braid soldered to pin 3 (the one in the middle) and cut it off with a pair of small pliers. Then put the plug back together and re-hook your system.

Do NOT try to lift a ground pin on your AC outlets: safety hazard!

You could also read further about star-grounding: a studio grounding scheme that I implemented in my studio and which safely insures hum and noise free systems.

hope it helps,

mx/
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20th February 2011
Old 20th February 2011
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iode131, thanks for the reply.

So, I have 2 TRS cables and 2 TS cables. I am not using XLR, because my audio interface does not output to XLR (I can only use XLR inputs). This is why I am using TRS<->TRS in the first place. I read a lot about the differences between TRS and XLR, and there doesn't seem to be any at all except for the shape of the connector.

So that means I must take one end of the TRS cable that is plugged into the monitor, do something "magic" with it (like killing the ground or something) and that will work?

Could getting better cables, like Mogami cables solve this issue?

If I attempt this, should I try it with my TS cables first, since if I mess those up, it won't matter?
#25
20th February 2011
Old 20th February 2011
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Quote:
Originally Posted by egervari View Post
iode131, thanks for the reply.

So, I have 2 TRS cables and 2 TS cables. I am not using XLR, because my audio interface does not output to XLR (I can only use XLR inputs). This is why I am using TRS<->TRS in the first place. I read a lot about the differences between TRS and XLR, and there doesn't seem to be any at all except for the shape of the connector.

So that means I must take one end of the TRS cable that is plugged into the monitor, do something "magic" with it (like killing the ground or something) and that will work?

Could getting better cables, like Mogami cables solve this issue?

If I attempt this, should I try it with my TS cables first, since if I mess those up, it won't matter?

Dude, this is what I suggested when asking about a soldering iron. Suggestion for wiring #8 in the Rane link I posted? Lifting the shield on the monitor side connector of your TRS.

Sure, you could just cut it but that may not be the fix then you'll likely have to re-strip and re-do the whole connection because now you'll be left with a shield that doesn't reach. Unsolder it to test or cut it if you feel daring.
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20th February 2011
Old 20th February 2011
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Oh I know that you suggested the same thing Ed. Sorry.

When I read the Rane's document, I don't I fully understood it until I woke up this morning. Something he said made more sense to me.

I don't have a soldering iron. I just bought these TRS cables. Now that I did some more research, I think the guy that sold to me locally really ripped me off. I paid $52 for them, but after going to the company's website (Pintech), they are on there for $12 each - $24 total. So the guy marked them up 200% :(

This brand (the C10-S) is also on sale on many places for like $9 too. Grr.

I am wondering if replacing one cheap TS cable with another cheap TRS cable could also be the problem. I think I'm going to return these before I mess with them. I was thinking that maybe even though they are "balanced", maybe it's so cheap that it's not working right? Would a better cable merely fix this problem? Some guy online had the exact same problem, and after trying 4 cables, he fixed it. I am thinking that might also be a possibility too.

Of course, maybe the 4th cable he tried had the ground cut in it already

I'll read that Rane's document one more time. I'll probably understand it a lot better. A lot of these electrical terms use words that mean other things, so I find that understanding it is a little hard because I don't exactly know all the terms.
#27
20th February 2011
Old 20th February 2011
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No worries. At least now you know what 'lifting' the ground means. I doubt swapping one cable for another would truly fix it but ya, I'd return those cables and get your money back if you're getting ripped off.

You really do need to try the ground lift thing though....somehow.


Good luck,

Warren
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20th February 2011
Old 20th February 2011
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I have 2 regular TS patch cables. I don't use them regularly, so if I were to just cut the shield and it didn't work, I could just throw them away. They are 10 years old and 30 feet long. Could I cut the shield on one of them and try it out? The B2031 accepts balanced and unbalanced inputs, so these TS cables work as it is. Is there anything I can do to get information using these crappy TS cables? If so, that might be a good place to start before wrecking a TRS cable like a Mogami if I were to purchase those.

In that Rane document, #15 looks like it's the normal configuration of the cable, so maybe it will just destroy the cable or maybe the speaker :/

I wish I had a crappy TRS cable just to see. It looks like it's worth trying if getting some better Mogami cables doesn't work.
#29
20th February 2011
Old 20th February 2011
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Quote:
Originally Posted by egervari View Post
I have 2 regular TS patch cables. I don't use them regularly, so if I were to just cut the shield and it didn't work, I could just throw them away. They are 10 years old and 30 feet long. Could I cut the shield on one of them and try it out? The B2031 accepts balanced and unbalanced inputs, so these TS cables work as it is. Is there anything I can do to get information using these crappy TS cables? If so, that might be a good place to start before wrecking a TRS cable like a Mogami if I were to purchase those.
No that won't work. You'd be cutting half the signal in an a/c circuit.

You can cut the shield in a balanced connection because there are three conductors in there. The signal would still be sent because two conductors are still in tact.

In your unbalanced cables the shield is ALSO a signal conductor so you'd just toast the cables if you cut them.
#30
21st February 2011
Old 21st February 2011
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Just lift the ground on your TRS jacks. You can always solder it back later if needed (if you decide to eventually learn how to solder, which I definitely recommend). The ground on a TRS jack is its sleeve. Cut it loose at the monitor end and get back to making music.

By the way, you CAN also lift the ground on an unbalanced connector if the device it's hooking up is grounded via the mains. AC signal does not mean that the current needs a "return way" or a closed circuit or something along those lines. What it needs is a ground reference: a voltage that tells it around what neutral value to alternate. That reference is provided by the mains ground. A certain kind of problems arises when different stages of the signal chain get different references.

mx/
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