Hey guys,

Alright I’m having an electricity problem, I think. Here’s my setup and how all my cables are hooked.

Mixer : Xone 92
CDJ : 2x CDJ800MK2 (RCA cables)
EFX : 1x EFX1000 (RCA cables)
Sampler : 1x PVDJ Grabber (RCA cables)
Speakers : Panasonic boombox bullshit (XLR to RCA cables)
Headphones : Pio HDJ1000 (1/4 stereo cable)

External soundcard : M-Audio FastTrack Ultra (1/4 TRS *grounded* cables)


Everything is plugged into a good powerbar (Belkin).


The problem is that I’m having an “electrical” sound into my soundcard, which is coming from my mixer. Let me explain myself more…

My MIX2 out from my Xone is plugged into my FastTrak Ultra. There is no conversions, it’s TRS to TRS. The cables are 25 feet long. 2 cables for stereo.

My FastTrack Ultra has 2 TRS cables going to my RETURN1 in my mixer. Again, no conversions, it’s TRS to TRS, 25 feet long. 2 cables for stereo.


The weird sound I’m getting can be heard on my main speakers (Panasonic) if I raise the fader of the SEND1 (which is connected to my FastTrak). Mixer was ON during that test. Mixer OFF, I can’t hear the noise of course.

I can also hear it in the headphones of my FastTrack, while I’m listening to what my mixer sending me, even if there are no faders up. Mixer ON or OFF, there are no differences, the noise is there.

Now, I did some tests yesterday and today. Note that nothing except my computer and my soundcard were ON during the followings tests. The mixer was OFF. I was using the M-Audio mixer control panel for testing, since I can see the noise in the spectrogram section.

Test 1 : Unplugged everything in the powerbar, except the mixer. The noise is still there. I unplugged the power from my mixer, no more noise. Note that the mixer is the only grounded connection. All other devices are 2 pins only…

Test 2 : With the mixer OFF and the only device plugged into the power bar, I unplug it from the power bar and plug it directly into the wall outlet. The noise is still there. I unplug it, the noise is gone.

Test 3 : I decide to use RECORD OUT on my mixer instead of MIX2. RECORD OUT is RCA…so I plug my RCA cables into my mixer and the noise disappears from the M-Audio mixer control panel. The interesting part is, I didn’t unplug the MIX2 cable yet and didn’t plug the RECORD OUT into my FastTrack. The other end of the cable was still in my hands. I then continued the steps and plugged the RECORD OUT correctly (RCA to TS) into the FastTrack Ultra with MIX2 disconnected and the noise was still gone. But this part of the test can’t be really relevant because the noise was still gone. I never managed to get the noise back, even after turning on and off everything and unplugging the RECORD OUT and putting back the MIX2.


I’m no electrical engineer what so ever. What I think, is that this is related to a ground problem. Since the mixer is the only device grounded and it seems to be the only device having this noise, this is what I came up with. My cables are good quality and they are TRS grounded cables so I doubt they are the problem. Also, the problem was there BEFORE I got these cables and the FastTrack. I paid attention to mixes I recorded on my old setup (RECORD OUT to LINE-IN Soundcard RCA to 1/8) and I had that noise. So this has nothing to do with my new equipment, I guess.

My computer’s UPS shows a site failure. According to Belkin, a site failure is usually related to grounding problem in the electricity circuit of the house. The problem is that, this is an apartment, not my house. I got no control on these kind of things. Is there any good way to find out if this noise is related to a grounding problem? If that’s the case, it can be dangerous for all my electrical stuff in the apartment.

So what do you think ? Am I thinking right or I’m totally off-track ? Is there any way I can fix this problem on my own without having to call an electrician ? Like some sort of electrical filter or what so ever, if the electricity is the problem here of course…

If you guys need a recording of the noise, I could probably do it tonight when I get back. Let me know…

Thanks,

Neo

Last edited by Neo Hacker on Feb-20-2008 at 15:22

sounds mysterious! but then electricity always does IMO!

one thing came to my mind that might have something to do with this that the mix2 on xone:92 is not true balanced, but impedance balanced! also i don't think the returns are balanced either.
your problem might have something to do with these things or then it might not.

edit:
i'd do a test like this if i were you:
unplug the cables that go from sound card to the return on the xone. check if noise is gone.
then if noise is gone plug the cables back in and unplug the cables from mix2 if noise is gone, then get xlr to trs cables (ar adaptors if such things exist) and plug them ti mix1 and then to the input on your sound card.

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Last edited by skip on Feb-20-2008 at 16:51

quote:

Originally posted by skip sounds mysterious! but then electricity always does IMO! one thing came to my mind that might have something to do with this that the mix2 on xone:92 is not true balanced, but impedance balanced! also i don't think the returns are balanced either. your problem might have something to do with these things or then it might not.

you're right. The Returns aren't balanced. They do accept TRS but unbalanced. But I guess this shouldn't be a problem from a balanced source to non balanced right ? I mean, my FastTrack outputs are balanced but my Returns aren't. Shouldn't the Xone handle the extra ground fine ? If it accepts TRS connector, it should...


As far as MIX2, I don't understand. What is Impedance balanced ? How is it different to "true" balanced ?

i'm not expert at this. but i was wondering about balanced cables and whatnot a while ago.
someone posted these links for me to read:
http://www.rane.com/note110.html
http://www.rane.com/note151.html
they were helpful to me at least. i can't remember if they have detailed info on them what impedance balanced means but i'm sure that can be googled. it's some sort of pseudo balancing from what i gather. the main point why it is used is apparently that you can connect balanced and unbalanced cables there easily and it'll work, or something like that.
i suspect that your problem lies there somewhere. i think you have a ground loop issue between your sound card and your mixer even though you'd think you wouldn't have one because you use balanced cables.
so if the noise goes away by breaking the loop mixer out - sound card in - sound card out - mixer in, i'd say the problem is definitely there.
the connection from your sound card out to the mixer input doesn't benefit anything at all from the balanced cables as if the other end is unbalanced, the signal is going to be unbalanced. and i don't know if what i am suggesting would solve your problem, but i just have a feeling it might.
but as i said, i don't know anything about electricity and it's all pretty much a mystery to me.

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quote:

Originally posted by skip i'm not expert at this. but i was wondering about balanced cables and whatnot a while ago. someone posted these links for me to read: http://www.rane.com/note110.html http://www.rane.com/note151.html they were helpful to me at least. i can't remember if they have detailed info on them what impedance balanced means but i'm sure that can be googled. it's some sort of pseudo balancing from what i gather. the main point why it is used is apparently that you can connect balanced and unbalanced cables there easily and it'll work, or something like that. i suspect that your problem lies there somewhere. i think you have a ground loop issue between your sound card and your mixer even though you'd think you wouldn't have one because you use balanced cables. so if the noise goes away by breaking the loop mixer out - sound card in - sound card out - mixer in, i'd say the problem is definitely there. the connection from your sound card out to the mixer input doesn't benefit anything at all from the balanced cables as if the other end is unbalanced, the signal is going to be unbalanced. and i don't know if what i am suggesting would solve your problem, but i just have a feeling it might. but as i said, i don't know anything about electricity and it's all pretty much a mystery to me.

Thanks for the links, I'll take a look when I got some time.

From what I've read on Google (quick search), impedance balancing is where the hot has more signal than the cold. Compared to true balancing where the hot and cold are equals. Really, I don't understand a lot but at least it gives me tips. It's supposed to be a pseudo and less expensive balancing.

So even if A&H says that the RETURNS accepts TRS but are unbalanced, they wouldn't have a ground to connect on the ring ? Right ? I'm totally blind here so please help me out understand that

As far as the loop you're talking about, I'm not sure. I unplugged the RETURNS and tried only the MIX2 so the only cables that were going between my soundcard and my mixer were the ouputs MIX2. There's no loop there from what I can tell. BUT, the MIX2 is impedance and I'm still trying to figure out the effects of plugging an impedance with a true balanced. I might just try these RCA to TS which is a totally non-balanced connection. BUT, the problem was there before I changed the setup and all connections were non-balanced...I was using RCA, TS and mini-jack (1/8") together to get everything working...

I don't think using balanced vs. non-balanced makes any difference as far as ground loops goes. I've had PLENTY of issues myself with those (with unbalanced connections), it's freaking annoying!

Does the ground loop exists without the mixer connected to the computer? Or is that the only factor? If it goes away with no computer connection, try using a ground-loop isolator between those two components. I had to do this connection my mixer up to my receiver in the other room, and it went away completely with an isolator.

I used this kind:
http://www.radioshack.com/product/i...rentPage=search

quote:

Originally posted by Ryan0751 I don't think using balanced vs. non-balanced makes any difference as far as ground loops goes. I've had PLENTY of issues myself with those (with unbalanced connections), it's freaking annoying! Does the ground loop exists without the mixer connected to the computer? Or is that the only factor? If it goes away with no computer connection, try using a ground-loop isolator between those two components. I had to do this connection my mixer up to my receiver in the other room, and it went away completely with an isolator. I used this kind: http://www.radioshack.com/product/i...rentPage=search

No. Unplugging the soundcard stops the noise. I can crank the volume at maximum level on my RETURN1 and I won't get any noise. Keep in mind that this noise can only be heard on the Panasonic speakers when playing music that comes from the soundcard (FastTrack -> RETURN1). CDJs won't generate that noise. And if I unplug MIX2, I can still hear the noise coming from RETURN1 in my Panasonic. Same thing if I unplug RETURN1 I can hear the noise from MIX2 on my soundcard. I don't know if I'm clear enough...it can be hard to explain...

A ground isolator ? Let just say for a moment that my appartment is well grounded. Shouldn't the ground prevent that exactly ? If I need a ground isolator, that's because somewhere I'm having a ground problem in my appartment... no ? I'd need a ground isolator for each of my TRS (so 4x)...

My place is supposedly well grounded as well... but i still have the ground loops!

One culprit I've DEFINITELY found: Telephone and/or coax cables coming into your computer. They can definitely cause a potential ground difference, because they aren't necessarily tied into your house ground.

In my place, the cable connection coming in would actually SPARK if you touched it to ground... I had to run it through a grounding block to get rid of that problem.

quote:

Originally posted by Neo Hacker No. Unplugging the soundcard stops the noise. I can crank the volume at maximum level on my RETURN1 and I won't get any noise. Keep in mind that this noise can only be heard on the Panasonic speakers when playing music that comes from the soundcard (FastTrack -> RETURN1). CDJs won't generate that noise. And if I unplug MIX2, I can still hear the noise coming from RETURN1 in my Panasonic. Same thing if I unplug RETURN1 I can hear the noise from MIX2 on my soundcard. I don't know if I'm clear enough...it can be hard to explain... A ground isolator ? Let just say for a moment that my appartment is well grounded. Shouldn't the ground prevent that exactly ? If I need a ground isolator, that's because somewhere I'm having a ground problem in my appartment... no ? I'd need a ground isolator for each of my TRS (so 4x)...

Last edited by Ryan0751 on Feb-20-2008 at 19:51

quote:

Originally posted by Ryan0751 I don't think using balanced vs. non-balanced makes any difference as far as ground loops goes.

i'm under the impression that a balanced connection should fix ground loop issues, but i'm not sure about it as i don't really understand the whole ground loop issue as i have never had one (yet).
i'm gonna get a laptop and traktor scratch at some point in my life so i might have to look more into ground loops in the future if i'm unlucky!

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Yeah supposedly since there's no signal path through the grounded shield on balanced cables, that you shouldn't see this problem. But who knows! These things are annoying to find and fix.

You're using TRS all the way through, or converters on the computer side?

I would try disconnection other peripherals from the computer (network, modems, etc) and see how you fare doing that as well.

I had the record out of my mixer connected to my laptop, and I got a ground loop! Even with the laptop UNPLUGGED. Very, very odd. It didn't seem like interference because the ground loop isolator got rid of it.

quote:

Originally posted by skip i'm under the impression that a balanced connection should fix ground loop issues, but i'm not sure about it as i don't really understand the whole ground loop issue as i have never had one (yet). i'm gonna get a laptop and traktor scratch at some point in my life so i might have to look more into ground loops in the future if i'm unlucky!

Last edited by Ryan0751 on Feb-20-2008 at 20:10

quote:

Originally posted by Ryan0751 My place is supposedly well grounded as well... but i still have the ground loops! One culprit I've DEFINITELY found: Telephone and/or coax cables coming into your computer. They can definitely cause a potential ground difference, because they aren't necessarily tied into your house ground. In my place, the cable connection coming in would actually SPARK if you touched it to ground... I had to run it through a grounding block to get rid of that problem.

I don't have any of this in my computer...what about my "Site Fault" warning on my UPS which states that there's a ground issue ?

Would a faulty ground in my appartment causes a noise like that ? As I said before, it's only when I unplug de mixer from the AC that the noise stops (with cables connected). And the mixer is the only device grounded (3 pins). My soundcard isn't. It is plugged into my UPS which is grounded but...I'm gonna run a test tonight :

Test 4 : Powering down the soundcard to see if I have noise on RETURN1.

Edit : I have 25 feet TRS all the way with no adapters at all. I only use adaptors for the EFX, Sampler and speakers (which I should get powered speakers this weekend with XLR builtin so no more XLR to RCA connector needed)

Lol, I dunno man... At least you have the troubleshooting mindset down

Go through an optical converter into you computer... hehe!