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fredgus

Horrible NOISE when 1/4" and VDI are both connected to HD500

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I discovered something quite disturbing this week.

In order to put stomp box pedals in front of the HD500, I was testing my Variax JT69US and HD500 by plugging in both the VDI and 1/4" cables to the guitar and setting the HD500 to accept only the GUITAR input. The result was an electronic sounding noise bed so loud, it was unbearable.  This happened with both the Mags and Variax PUs. Unplugging the VDI connection and operating on just the battery works fine with no noise. There's obviously electrical interference causing this issue.

 

Has anyone else experienced this or can reproduce it on their rig? Any Line 6 techs have an explanation and/or fix for it?

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Typical result of a Ground Loop.

Diagnosing and Fixing Ground Loops to Prevent AC Hum/Buzz
http://www.ebtechaudio.com/findloop.pdf


http://www.glab.com.pl/tip_9_en

 

 

 

Insert one of these between your last effect and the 1/4" input on the HD500

he-2_left_bottom-45f2c7549b6a89413c0fa68

 

 

or 

 

Pyle PHE300 is $14
http://www.mcmelectronics.com/product/555-16050?utm_source=Criteo&utm_medium=Retargeting&utm_term=555-16050&utm_campaign=criteo+retargeting&CA_6C15C=530004080000223021

 

555-16050.jpg

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So, can there be a ground loop created between the JTV69 and the HD500 (2 devices) via the VDI Cat5 network cable when a 1/4" mono plug is also directly connected between the guitar and HD500?  Keep in mind, the ground is being lifted by the AC/DC adapter as it converts the voltage for the HD500. I don't have any other pedals yet in the chain between the guitar and the POD. When I remove either the Cat5 or the 1/4" cables, the noise goes away.  So, there obviously is a noise loop between the two when power is applied from the HD500 through the Cat5. Would the Pyle or Morely help with this or could something else be going on? 

 

Does anyone know how much voltage is being sent through the Cat5 and which wire pairs are being used?

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Yup - sounds like a ground loop. Your connection from your output of the HD500 establishes a ground from your amp, and your pedals(s) external to the HD500 are introducing a separate ground path at a slightly different potential - doesn't take much actual voltage to make a loud buzz at the low level of an instrument output. Can I assume you have wall power to your external stomp boxes or are they on batteries? Try headphones and disconnect from your power amplification -- when hooked to your external stomps. If the noise goes away in that circumstance, you have a ground loop between your stomps and your amp meeting up in the HD500....

 

I built myself a 1:1 isolation audio transformer for when I hook my HD500(X) to my desktop pc. I place the isolation transformer between my HD500(X) and my amp for when I use it hooked up to both. Otherwise, I get the ground loop buzz in that condition. The Ebtech device above is simply a commercial iso transformer. It would probably also work between your HD500 and you amplification. There are others out there. If you use the XLR outputs instead of the 1/4" outs, try using the XLR Ground/Lift Switch in the "Lift" position....

 

Some things to try...

 

Dave

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I had ground loop noise using the 1/4 outs when connected to my laptop (laptop power supply plugged in).  I switched to using the XLR and the noise was gone completely.  I am connected to a powered PA speaker that has either 1/4 in or XLR in.  I have never tried that setup with both the 1/4 and VDI connected though.  No reason for me to do that.  I use VDI for Variax and 1/4 in for my other guitars.

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I have noticed a pretty big difference in sound between the VDI connection and the 1/4" and I prefer how the guitar sounds when the 1/4" is plugged in. Out of the 2 batteries I received with the guitar, only one of them holds a charge, but only for about 1 day. These batteries seem to wear out very quickly. To power the guitar and get the preferred sound of the 1/4" connection, I used both plugs in order to get power to the CPU on the guitar. That's when the noise became noticeable. I have NOT been running these tests through my amp.  I've tested only with headphones and also with an XLR connection to my audio interface, which gets routed through my Central Station, then reference monitors. Both cases produce the noise.  I am going to take the gear to a different room on a different circuit and try there as well to see if the issue persists.

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Should you run into noise when connected via USB to your computer  - I have developed a good bit of debug / solutions here

 

http://www.vguitarforums.com/smf/index.php?topic=367.0

 

and more Audio Ground Loop debug / solutions here

http://www.vguitarforums.com/smf/index.php?topic=2078.0

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Not sure why your batteries don't work for you.  Mine are 2 years old and they hold a charge just fine.  I have never had trouble with this kind of battery.  I play with the battery sometimes.  Battery is the most noiseless way to play.

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