Hi. I'm having problems with some excessive hum on my Behringer HA4700 powerplay. I have it on top of my desk with my Layla 3G, Studio Projects VTB1 and M-Audio DMP3 stacked above it.
My setup is wired as follows :-
Outputs 1&2 on Layla 3G - Inputs 1&2 SM Pro Audio M Patch2
Outputs 3&4 M Patch2 - Main Ins 1&2 Powerplay HA4700
Balanced out VTB1 - Input 1 Layla 3G
Line Out VTB1 - Direct In Powerplay HA4700
I have used balanced leads throughout and have tried swapping leads but the problem still occurs.
Please could you assist with my problem.
Many Thanks
Richard
Hum on Headphone Amp !?
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- KVRAF
- 2824 posts since 22 Mar, 2006 from cornwall
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- KVRAF
- 16866 posts since 8 Mar, 2005 from Utrecht, Holland
Probably a ground loop... Wherever the ground can travel more than one way to a device you may get that issue.
Either feed mains power without ground, or lift the ground at one of the balanced connections.
Either feed mains power without ground, or lift the ground at one of the balanced connections.
We are the KVR collective. Resistance is futile. You will be assimilated. 
My MusicCalc is served over https!!
My MusicCalc is served over https!!
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- KVRian
- 1055 posts since 19 Feb, 2003
Is >everything< you've got plugged into it on the same circuit??
(Don't be fooled by the wall plugs all being in the same room. Sometimes circuits are split in a house so that if one circuit goes out, lights will stay on with the other circuit...)
(Don't be fooled by the wall plugs all being in the same room. Sometimes circuits are split in a house so that if one circuit goes out, lights will stay on with the other circuit...)
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- KVRAF
- Topic Starter
- 2824 posts since 22 Mar, 2006 from cornwall
Yes everything is coming from one socket. I have taken two plug boards from the one socket. Would that make any difference if they are in different plug boards? I'll swap them around later to see if that makes any difference.timobrien wrote:Is >everything< you've got plugged into it on the same circuit??
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- Banned
- 78 posts since 29 Jun, 2007
Unplug everything. Start with the HP amp, monitoring as you go, and plug in one device at a time until you find the culprit.
Also, check the manufacturers specs for balanced/unbalanced i/o. Connecting an unbalanced to balanced connection leaves the neutral floating, which can also cause a hum. Any connection that is unbalanced, no matter what it goes from or to, use unbalanced cable, as the connection is unbalanced. Keep the cable under 15 ft, and away from any AC, wall warts, CRT monitors, and other sources of RFI noise.
Also, check the manufacturers specs for balanced/unbalanced i/o. Connecting an unbalanced to balanced connection leaves the neutral floating, which can also cause a hum. Any connection that is unbalanced, no matter what it goes from or to, use unbalanced cable, as the connection is unbalanced. Keep the cable under 15 ft, and away from any AC, wall warts, CRT monitors, and other sources of RFI noise.
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- KVRAF
- Topic Starter
- 2824 posts since 22 Mar, 2006 from cornwall
Ok. I've tried re=wiring things a little differently and the noise has more than halved the noise problem:-
Outputs 1&2 Layla 3G - Inputs 1&2 SM Pro Audio M Patch2
Line Out VTB1 - Mic In Tapco Blend 6 mixer
Outputs 3&4 M Patch2 - L&R Stereo Channel 3/4 Tapco Blend 6
Main L&R Outputs Tapco Blend 6 - Main L&R Inputs HA4700
Any ideas what might have been causing the problem? Bizarrly when I had it wired up the old way when I turned the volume of the M Patch2 up (to hear more backing) the hum got louder? How is this possible because the M Patch2 is passive?
Outputs 1&2 Layla 3G - Inputs 1&2 SM Pro Audio M Patch2
Line Out VTB1 - Mic In Tapco Blend 6 mixer
Outputs 3&4 M Patch2 - L&R Stereo Channel 3/4 Tapco Blend 6
Main L&R Outputs Tapco Blend 6 - Main L&R Inputs HA4700
Any ideas what might have been causing the problem? Bizarrly when I had it wired up the old way when I turned the volume of the M Patch2 up (to hear more backing) the hum got louder? How is this possible because the M Patch2 is passive?
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- KVRist
- 56 posts since 2 Apr, 2007
I had similar problem... I changed the cables I was using and most of the problem went away... Some cables causing more hum... Also try to keep cables as short as possible... But it will never be totally silent... there will be an amount of hum.. But it can be decreased to a acceptable level...
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- KVRAF
- Topic Starter
- 2824 posts since 22 Mar, 2006 from cornwall
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- Banned
- 78 posts since 29 Jun, 2007
Unplug everything. Start with the HP amp, monitoring as you go, and plug in one device at a time until you find the culprit.dickiefunk wrote:Ok. I've tried re=wiring things a little differently and the noise has more than halved the noise problem:-
Outputs 1&2 Layla 3G - Inputs 1&2 SM Pro Audio M Patch2
Line Out VTB1 - Mic In Tapco Blend 6 mixer
Outputs 3&4 M Patch2 - L&R Stereo Channel 3/4 Tapco Blend 6
Main L&R Outputs Tapco Blend 6 - Main L&R Inputs HA4700
Any ideas what might have been causing the problem? Bizarrly when I had it wired up the old way when I turned the volume of the M Patch2 up (to hear more backing) the hum got louder? How is this possible because the M Patch2 is passive?
Also, check the manufacturers specs for balanced/unbalanced i/o. Connecting an unbalanced to balanced connection leaves the neutral floating, which can also cause a hum. Any connection that is unbalanced, no matter what it goes from or to, use unbalanced cable, as the connection is unbalanced. Keep the cable under 15 ft, and away from any AC, wall warts, CRT monitors, and other sources of RFI noise.