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apex
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Joined: 23 Feb 2010
Posts: 2340
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 Posted: Wed Jun 27, 2012 3:15 am Post subject: Noise coming from house speakers at my church... Help |
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Hi guys,
Kronos / Motif XF connected to church speakers directly to floor (which runs to our house console) very bad buzzing sound that got louder and louder with raising of the gain or the channel fader...
any suggestions? cables (balanced vs unbalanced... ) could that be the problem? how can I fix it.
thanks.
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MarPabl
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Joined: 24 Sep 2011
Posts: 938
Location: MX
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| Posted: Wed Jun 27, 2012 4:49 am Post subject: |
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I think this thread may be helpful: XF and laptop: Ground Loop Fixed!!
You can use balanced cables with the Kronos, but not with the Motif XF
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SanderXpander
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Joined: 29 Jul 2011
Posts: 7860
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| Posted: Wed Jun 27, 2012 5:36 am Post subject: |
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Balanced cables would probably make it worse if it's a ground loop.
But yeah you can usually get little adapters that lift the ground off your plug. I always carry one for laptop gigs. |
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apex
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SanderXpander
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Joined: 29 Jul 2011
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| Posted: Wed Jun 27, 2012 6:18 am Post subject: |
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| Unground the Kronos. |
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1jordyzzz
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Joined: 03 Mar 2012
Posts: 688
Location: Indonesia
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| Posted: Wed Jun 27, 2012 6:19 am Post subject: |
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it's happened at me once, but my problem is simple.. turns out that i forget to set the input volume knob to zero.. instead, it went to max and deliver great amount of noise.. there are two inputs on the back of the kronos.. try to turn them off.
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Korg Kronos 88, Yamaha PSR s910, Korg C720, Yamaha DTX 520, Focusrite Scarlett 18i6, a pair of Yamaha HS80 in (soon not to be) an unproperly treated room.. |
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.Jens
Senior Member
Joined: 06 Dec 2011
Posts: 383
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| Posted: Wed Jun 27, 2012 7:00 am Post subject: |
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| SanderXpander wrote: | | Balanced cables would probably make it worse if it's a ground loop. |
 How would they make it worse? Normally, you get better isolation against hum, you get a +3dB signal level "for free" (and therefore +3dB in SNR), and on top you have the possibility to fix a ground loop by lifting the ground on one end of the line. That's not possible with an unbalanced.
What effect do you have in mind introducing new or more serious problems by using balanced cables compared to unbalanced ones?
BTW: Checking the inputs is a very good idea. Checking the rest of the equipment for ground loops, too. |
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Hooch
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Joined: 07 Oct 2011
Posts: 99
Location: Northern California USA
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| Posted: Wed Jun 27, 2012 7:21 am Post subject: |
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Get DI's for everything.
Balanced out or unbalanced out of your kit.
It will solve all your Problems.
I highly recommend Radial. The make a basic high quality
mono and stereo DI.
You'll carry them with you for life.
Hooch |
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SanderXpander
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Joined: 29 Jul 2011
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| Posted: Wed Jun 27, 2012 7:54 am Post subject: |
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| .Jens wrote: | | SanderXpander wrote: | | Balanced cables would probably make it worse if it's a ground loop. |
How would they make it worse? Normally, you get better isolation against hum, you get a +3dB signal level "for free" (and therefore +3dB in SNR), and on top you have the possibility to fix a ground loop by lifting the ground on one end of the line. That's not possible with an unbalanced.
What effect do you have in mind introducing new or more serious problems by using balanced cables compared to unbalanced ones?
BTW: Checking the inputs is a very good idea. Checking the rest of the equipment for ground loops, too. |
If you can't lift the ground on one end, a balanced cable gives you more hum than an unbalanced one. At least in my experience. |
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michelkeijzers
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Joined: 08 Feb 2007
Posts: 9113
Location: Netherlands
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| Posted: Wed Jun 27, 2012 8:36 am Post subject: |
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| Hooch wrote: | Get DI's for everything.
Balanced out or unbalanced out of your kit.
It will solve all your Problems.
I highly recommend Radial. The make a basic high quality
mono and stereo DI.
You'll carry them with you for life.
Hooch |
I also would recommend a DI box (easy to try).
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.Jens
Senior Member
Joined: 06 Dec 2011
Posts: 383
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| Posted: Wed Jun 27, 2012 9:17 am Post subject: |
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| SanderXpander wrote: |
If you can't lift the ground on one end, a balanced cable gives you more hum than an unbalanced one. At least in my experience. |
That's quite contrary to my experience, and also contrary to what balanced signal transmission is all about. The main idea is that hum will have the same amplitude on the "+" and "-" lead and cancels out when subtracting both signal parts.
If you encounter more hum with balanced cables, I would suspect there is something else going wrong. For example, on some 1/4" connector types (depending where the latch for the shaft contact sits actually) there might arise a problem with improper mass contact when inserting a (balanced) TRS jack into a TS socket. If that is the case, a balanced cable will not offer any benefit, however - because the output is already unbalanced. But if a device has dedicated balanced outs, a balanced connection is the better choice normally.
Anyway: To have a DI at hand is a very good idea, that's right. It accepts both kinds of input, has switchable ground lift, switchable pad, protects your gear from (faulty) phantom power and allows the FOH tech to operate at mic level, which is often easier than padding at the desk - and reduces crosstalk sometimes on very long multicores. |
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SanderXpander
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Joined: 29 Jul 2011
Posts: 7860
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| Posted: Wed Jun 27, 2012 5:40 pm Post subject: |
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| Strange. I'm sure you know what you're talking about. I'll have to check and see what went wrong for me then. What is the difference between a ground lift and using an unbalanced cable then? |
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apex
Platinum Member
Joined: 23 Feb 2010
Posts: 2340
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| Posted: Wed Jun 27, 2012 7:38 pm Post subject: |
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| michelkeijzers wrote: | | Hooch wrote: | Get DI's for everything.
Balanced out or unbalanced out of your kit.
It will solve all your Problems.
I highly recommend Radial. The make a basic high quality
mono and stereo DI.
You'll carry them with you for life.
Hooch |
I also would recommend a DI box (easy to try). |
In the research that I've done since last night, this seems to be the best option. I contacted my church and have been given permission to go and purchase 2 DI boxes and 2 XLR mic cables to connect the DI box to our floor inputs. I'll let you guys know what happens.
thanks for the input. GO KRONOS.
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.Jens
Senior Member
Joined: 06 Dec 2011
Posts: 383
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| Posted: Wed Jun 27, 2012 7:53 pm Post subject: |
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| SanderXpander wrote: | | Strange. I'm sure you know what you're talking about. I'll have to check and see what went wrong for me then. What is the difference between a ground lift and using an unbalanced cable then? |
As you will know already, you need two wires to transmit an audio signal through a cable.
In an unbalanced cable, you have a single wire carrying the signal, surrounded by a shield, which serves as ground, shield and second signal "wire" at the same time. You can't lift ground here, because this would interrupt the signal path.
In a balanced cable, you have two wires inside a common shield. Each of these wires carries the same signal, one with normal and one with reverse polarity. The shield just has to be shield and ground, no signal. Because only the difference between the two wires is relevant for the signal, it doesn't matter which potential the shield is on. In case you have trouble with leak currents through the shield (hum loop), it doesn't hurt the signal if you interrupt the loop by lifting (disconnecting) the shield on one end of the cable. The shield will work anyway, unless you disconnect it from ground on both ends. Even then, there will be a shielding, but a quite bad one.
The crucial thing to balanced transmission is that the whole chain must be balanced, i.e. cable as well as both in- and output have to be symmetric (balanced). If one component is unbalanced, the whole chain becomes unbalanced immediately. That's not bad, but it's the same as using an unbalanced cord.
Problems, however, may arise if the connectors are not matching well (which is seldom, but possible). For example, the latch of a TS jack intended for shaft inadvertedly shortcuts ring and shaft of the jack, or having a bad contact due to the small gap between ring and shaft. Or - nearly impossible - contacting ring instead of shaft. If then a ground lift is applied somewhere, that may cause trouble.
BTW: An unbalanced in- or output does not necessarily makes the whole chain unbalanced, if the signal is properly transformed by a DI. |
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JPWC
Platinum Member
Joined: 29 Oct 2010
Posts: 638
Location: Bay Area, CA
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| Posted: Wed Jun 27, 2012 8:14 pm Post subject: |
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Trouble shooting:
Disconnect keyboards at floor connection: if noise goes away problem is with the cable/connection between keyboard and floor jack. replace cable.
If buzz is still present go to church mixer and unplug the cable associated with your floor connection. If noise still present problem is with house PA system, i.e. mixer.
Before you try anything too complicated, try a different cable, try a different source (another keyboard or a microphone or even an iPod)
Let us know your results, and describe the house system.
ensure good quality SHIELDED cables and connects are used throughout the system. (Can be Balanced also, see discussion above.)
If floor connect goes straight to Microphone input on mixer, DI is required. Keyboards tend to like line level (-10 to +4db) signal inputs, balanced connection should improve noise floor.
Ground should never be cut on cables, if it's cut on the signal side, buzzes & hums will be heard. Use a DI box which will single end the cable, i.e. disconnect ground between the two devices, but the shield drain wire will still be connected at one end of the cable and provide the shielding function. Sometime device float or don't have the same potential between them. When you cut the ground on the power connection equipment can become dangerous.
Unshield cable should not be used. don't use speaker cables
your described symtoms sound like a bad cable as this is usually indicating by BUZZ, problem where disconnecting ground on equipment solve the problem are usually HUMS
Make your own cables, use canare star-quad cable. This approach has solved many of my problems. Instead of a DI, there are simple iso-boxes that use a transformers to break the direct connection, very little change in signal level and impedance.
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Last edited by JPWC on Thu Jun 28, 2012 3:03 am; edited 2 times in total |
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