lcmxr6
Hello, I'm having an issue at the club I work at. Its not software related but I thought someone here might be able to offer me some advice. I'm having a feedback problem (gound loop I think) when I plug in my HDMI cable to the splitter. It would seem the problem is with my laptop. I have everything plugged into hum ex ground loop isolators but that doesn't seem to make a difference. I'm feeling a little stuck at the moment. Anyone have any suggestions?
Mensajes Sat 19 Mar 11 @ 3:00 pm
Dazmax
Hi mate.
Do you still get the problem if the laptop power cable is unplugged? If not you may find that a change of laptop power supply to a unit which is double insulated helps. This can also ring true for any external monitor you have, if you use one.
Try disconnecting each item in turn from the laptop while the HDMI cable is hooked up. Start with the laptop power supply and any external usb equipment, then audio side and try to see if any of the other devices you have connected are completing the loop. Isolating a loop in the video side is quite difficult but isolating the rest to break the loop should not be too hard.
Make shure you use the shortest leads you can, especialy for USB and any unbalanced audio lines.
If you have balanced aoudio outputs to your amps or an in house mixer you can isolate the screen in the balanced cable by snipping the screen(usualy a braided or heavier looking wire without insulation) conection inside the balanced line plugs at the end that conects to your sound card or mixer. Insulate the screen and re assemble the plugs
When you plug your power supplies in, work in a sequence. I find that it can make a real difference if, for example you use a multiway extension chord. Plug in and do this so that the heaviest power consumer is from the end of the extension where the supply cable enters. For example first your laptop then your external HDD then the sound card/mixer.
Lastly check if any of the isolators that you are using in the audio chain are of the transformer or the resistive type. The transformer type will provide total phisical isolation and will perform better.
Oh and obviously Do Not Lift, Disconect or otherwise mess with, any of your mains electrical earth/ground conections. If you are using grouded mains connectors make shure that they are of the non reversable type (should not be an issue in the US).
Daz
Do you still get the problem if the laptop power cable is unplugged? If not you may find that a change of laptop power supply to a unit which is double insulated helps. This can also ring true for any external monitor you have, if you use one.
Try disconnecting each item in turn from the laptop while the HDMI cable is hooked up. Start with the laptop power supply and any external usb equipment, then audio side and try to see if any of the other devices you have connected are completing the loop. Isolating a loop in the video side is quite difficult but isolating the rest to break the loop should not be too hard.
Make shure you use the shortest leads you can, especialy for USB and any unbalanced audio lines.
If you have balanced aoudio outputs to your amps or an in house mixer you can isolate the screen in the balanced cable by snipping the screen(usualy a braided or heavier looking wire without insulation) conection inside the balanced line plugs at the end that conects to your sound card or mixer. Insulate the screen and re assemble the plugs
When you plug your power supplies in, work in a sequence. I find that it can make a real difference if, for example you use a multiway extension chord. Plug in and do this so that the heaviest power consumer is from the end of the extension where the supply cable enters. For example first your laptop then your external HDD then the sound card/mixer.
Lastly check if any of the isolators that you are using in the audio chain are of the transformer or the resistive type. The transformer type will provide total phisical isolation and will perform better.
Oh and obviously Do Not Lift, Disconect or otherwise mess with, any of your mains electrical earth/ground conections. If you are using grouded mains connectors make shure that they are of the non reversable type (should not be an issue in the US).
Daz
Mensajes Sat 19 Mar 11 @ 4:00 pm
lcmxr6
Thank you for the response, the information you provided is very helpful. The hum is there with or without the power cable plugged in. I had an issue with this system in the past so I bought the hum ex filters. I was also having a problem with my mixer (denon dnx1600). This really struck me as odd because I use XLR balanced mains. I was able to eliminate all humming by plugging everything into a power strip that had a hum ex isolator between it and the wall. As soon as I started doing video however the problem returned. It only happens with a plug in the HDMI cable. I thought the cable itself might be a problem but I've tried two with no luck. The booth is a structure built above the floor and all the amps are in a room below. I'm thinking somewhere something is not grounded right. Everything is really old though so I wouldn't know where to start lol.
Mensajes Sat 19 Mar 11 @ 4:27 pm
Dazmax
Hi mate.
Change of order here then. If you can lift the screen connection on the balanced line cables from your mixer it may well do the trick. Having the hum ex isolator will help to isolate ground loops produced by your equipment but I suspect the loop is being created between the ground connection on the HDMI cable and the screen connections on the balanced line cables to the amp rack. You only need to break one part of this chain to get rid of the hum. I also suspect that the amp rack is grounded ok. Oddly, the very thing that is used to give extra protection from electrical faults is what "causes" ground loops LOL.
A little trick here would be to make up, or get someone to make you a short (6" or so) pair of balanced line cables wired with the ground/screen pin (pin 1) lifted. You can then use these as audio ground lifts in any venue. This is a very safe method BTW.
When you get to the club just plug them in to your Denon XLR outs and then plug the club systems cables into these. This will break any loop between the amp rack and your gear.
good luck
Daz
Change of order here then. If you can lift the screen connection on the balanced line cables from your mixer it may well do the trick. Having the hum ex isolator will help to isolate ground loops produced by your equipment but I suspect the loop is being created between the ground connection on the HDMI cable and the screen connections on the balanced line cables to the amp rack. You only need to break one part of this chain to get rid of the hum. I also suspect that the amp rack is grounded ok. Oddly, the very thing that is used to give extra protection from electrical faults is what "causes" ground loops LOL.
A little trick here would be to make up, or get someone to make you a short (6" or so) pair of balanced line cables wired with the ground/screen pin (pin 1) lifted. You can then use these as audio ground lifts in any venue. This is a very safe method BTW.
When you get to the club just plug them in to your Denon XLR outs and then plug the club systems cables into these. This will break any loop between the amp rack and your gear.
good luck
Daz
Mensajes Sun 20 Mar 11 @ 12:12 am
lcmxr6
Dazmax wrote :
Hi mate.
A little trick here would be to make up, or get someone to make you a short (6" or so) pair of balanced line cables wired with the ground/screen pin (pin 1) lifted. You can then use these as audio ground lifts in any venue. This is a very safe method BTW.
When you get to the club just plug them in to your Denon XLR outs and then plug the club systems cables into these. This will break any loop between the amp rack and your gear.
A little trick here would be to make up, or get someone to make you a short (6" or so) pair of balanced line cables wired with the ground/screen pin (pin 1) lifted. You can then use these as audio ground lifts in any venue. This is a very safe method BTW.
When you get to the club just plug them in to your Denon XLR outs and then plug the club systems cables into these. This will break any loop between the amp rack and your gear.
This sounds like the solution I'm looking for. I don't know much about making cables though. I have wired Lan cables before but thats it. I'm guessing it's possible then to buy the materials online to make this at home?
Mensajes Sun 20 Mar 11 @ 4:49 pm
Tear Em 'Up
Try here ---> http://procablesnsound.com/PCNS_Main.asp
Mensajes Sun 20 Mar 11 @ 5:16 pm
Dazmax
Hi mate.
here is an alternative solution. This is from a UK based company but a quick search in your area should turn these up.
http://www.studiospares.com/adaptors-xlr/hosa-ground-lift-adaptor/invt/578780/
Daz
here is an alternative solution. This is from a UK based company but a quick search in your area should turn these up.
http://www.studiospares.com/adaptors-xlr/hosa-ground-lift-adaptor/invt/578780/
Daz
Mensajes Mon 21 Mar 11 @ 12:42 am