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Hum And Noise When Using Usb, But Usb Isolator Won't Allow Driver To Load

hum noise usb isolator ground

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#1 fhludlow

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Posted 09 June 2013 - 08:13 AM

I've just been through the harrowing experience of finding all the ground loops and other sources of noise when trying to use HD500 with computer and guitar amp simultaneously.  I had to use a 3 prong to 2 prong adapter on a tube phono preamp (which of course the phono preamp doesn't like), disconnect the FM antenna coax that goes to other recievers in my house (and yes I have a coax isolator that solved a similar problem I had a long time ago, it didn't work in this case), disconnect audio connection from jam room/studio to another reciever in another room, and put my Profire 2626's power cord and a few other things on a power strip on an isolation transformer also with no third prong ground connection.

 

So if I completely change many things in my system, losing several aspects of functionality, I can actually reduce all the sources of hum and noise coming out of the guitar amp.

 

However, since every single other device I use has always been perfectly happy the way things are, the obvious solution is use a device to galvanically isolate the USB signal between the HD500 and computer.

 

There are several on the market, probably based on the same ADUM3160 or adum4160 chips.   http://www.analog.co...lation/fca.html

 

I bought this, it has the adum3160 chip.

http://www.ebay.com/...=item1e794e104f

 

When the HD500 is plugged in through the USB isolator - ALL the different noises are gone!  BUT - the driver won't load!!  It sees that it is an HD500 but will not load the driver.  I tried every conceivable combination of cables, with/without USB hub before/after the isolator, TWO completely different computers, etc.

 

Does anyone have any insight on if a device like this can possibly work with the HD500?  Why would the OS be able to see it, retrieve the plug-n-play info to correctly recognize it as specifically a Line 6 HD500, but refuse to load the driver??
 

I'm probably going to end up buying other ones to try.  I know Line 6 sometimes uses their hardware as licensing dongle so I'm afraid they may deliberately break the functionality of a USB isolator like this somehow?  Every other USB device I tried works fine through the isolator.

 

http://www.amazon.co...=A1PO6NTQYFXQX9

http://www.amazon.co...pd_sim_sbs_pc_4


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#2 DeanDinosaur

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Posted 09 June 2013 - 08:41 AM

When the HD500 is plugged in through the USB isolator - ALL the different noises are gone!  BUT - the driver won't load!!  It sees that it is an HD500 but will not load the driver.  I tried every conceivable combination of cables, with/without USB hub before/after the isolator, 

Try reinstalling the driver. The reason I say this is that I noticed when I change the USB location where the HD USB is plugged, I usually have to reinstall the driver. When you get to the point in the installation where it asks you to plug the POD HD, if you plug in the isolater and it install then you're good, if it doesn't then I recommend returning it since the pod technically doesn't support HUBs, so it might be seeing or not seeying the isolater as it might be similar to a hub in someway. good luck. (don't forget to try the Isolator in a different USB port if it stil doesn't work)


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#3 fhludlow

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Posted 10 June 2013 - 09:21 AM

Good tips, thanks!

 

Evidently, and I can not find any documentation of this, the HD500 will only work with "high speed" USB 2.0  "480 Mbit/s (effective throughput up to 35 MB/s or 280 Mbit/s) (now called "Hi-Speed")".  I have no idea why it would need so much bandwidth for changing patch settings, and it certainly needs a tiny fraction of that for audio.  Evidently it is not capable of falling back/negotiating at older/slower standards. I would love some official confirmation of this, I can't find it documented anywhere.  I found some discussion that people who went from XT to X3 found their USB ports were suddenly incompatible. Presumably the HD line continues this, even though there has not been a need for the increased bandwidth since before the XT line.

 

All usb isolator devices on the market, short of some very expensive (like $1,000+) medical devices or whatever, can only do "full speed" - "USB 1 specified data rates of 1.5 Mb/s (Low-Bandwidth) and 12 Mb/s (Full-Bandwidth)."  So the fact that every single USB isolator product claims "full speed" and either USB 2.0 "compliant" or "compatible, it turns out to be misleading, and "full" is slower than "high."

 

Very unfortunate, since it would solve so many problems that so many people are having. I have to admit I've wondered why Line 6 doesn't think about integrating USB isolation directly into the product, since so many people have so much frustration.  It would make it a much more robust product than many of their competitors.

 

I guess I'll try to another tactic of isolating the HD500 from the guitar amp's input with a transformer.  I made a "re-amp" box out of a Jensen transformer in the past, I think a 1:1 transformer will work? 

 

https://www.edcorusa...p/80/tpc10k-10k

 

It only solves the problem of noise/ground loop hum into the guitar amp's input, not the rest of the monitoring/recording system, but at this point the product can not be used for its intended purposes in my system and I might just return it.


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#4 DeanDinosaur

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Posted 10 June 2013 - 10:00 AM

 I would love some official confirmation of this, I can't find it documented anywhere. ....

Bottom of page 9.1 in the advanced operation manul "Once installation is complete, just connect your device directly to a USB 2.0 port on your computer and power On your POD HD500. Note that POD HD500 requires the use of a 
USB 2.0 port on your computer (not into a USB hub)"
 
I was like you when I first got mine. I was surprised it didn't work with my old laptop until I found out that the old laptop didn't have USB 2. Initially I wasn't happy, but then I thought it was a good thing and figured the audio driver will have to be more robust than POD XT and tone port etc, and it was.
 
I think the bandwidth is needed because as you edit, you can also run the POD as an audio interface  with a full fledged ASIO driver that is really decent that can record and play multitracks.

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#5 pfsmith0

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Posted 10 June 2013 - 07:34 PM

Yes, I wish the HD500 used TOSLINK instead of S/PDIF. That would have solved your problem. it seems like a natural fit with all the ground loop issues common to electric musical instrument setups.


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#6 davidb7170

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Posted 10 June 2013 - 08:10 PM

I built an audio isolation box for 1/4" in & out, due to the ground loop created when I had my HD500 (actually built it when I had my XTL, and also used it with my X3L) plugged into the usb on my pc and my amp. The 1 to 1 transformer cost about a buck from Allied Electronics, the project box was 3 or 4 bucks as I recall, and a couple of 1/4" jacks. I only use it when I'm going to connect my HD500 to the pc and my amp when editing the JTV or the HD500 via the pc. I put it in line in the 1/4" to my amp, and shazaam, the buzz is gone...

 

You don't need it if you unplug from the amp and use headphones. Amp on or off -- the ground loop is still there if you're still plugged into the amp. Turns out my pc and my amp/HD500 outlets are on 2 different house circuits, which make ground loops worse.

 

Dave

 

 

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#7 line6lcasey

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Posted 27 November 2013 - 06:50 AM

I built an audio isolation box for 1/4" in & out, due to the ground loop created when I had my HD500 (actually built it when I had my XTL, and also used it with my X3L) plugged into the usb on my pc and my amp. The 1 to 1 transformer cost about a buck from Allied Electronics, the project box was 3 or 4 bucks as I recall, and a couple of 1/4" jacks. I only use it when I'm going to connect my HD500 to the pc and my amp when editing the JTV or the HD500 via the pc. I put it in line in the 1/4" to my amp, and shazaam, the buzz is gone...

 

You don't need it if you unplug from the amp and use headphones. Amp on or off -- the ground loop is still there if you're still plugged into the amp. Turns out my pc and my amp/HD500 outlets are on 2 different house circuits, which make ground loops worse.

 

Dave

Do you have a schematic and part numbers for everything to make this device? I have terrible hum when my laptop is plugged in to my HD500x. Difference between yours and mine is that all the equipment is on the same circuit.

 

Thanks


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#8 still_fiddlin

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Posted 27 November 2013 - 07:21 AM

Any way you can try a notebook computer running on battery power? Not what you want but it could be cheaper!

I'm a little puzzled about connecting the pod to a PC and amp at the same time; ie., what are you trying to do?
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#9 fhludlow

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Posted 27 November 2013 - 09:09 AM

Do you have a schematic and part numbers for everything to make this device? I have terrible hum when my laptop is plugged in to my HD500x. Difference between yours and mine is that all the equipment is on the same circuit.

 

Thanks

It's very simple.  Here's an example transformer that should work great.  You just run the two wires of guitar signal into the two inputs, and run it out to the amp from the two outputs.  This tranny has center taps for using balanced configurations, just ignore them.
http://www.edcorusa....p/123/pc10k-10k
 


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#10 davidb7170

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Posted 27 November 2013 - 08:56 PM

This is the what I sent to line6lcasey:

 

The audio isolation transformer is a Triad Magnetics TY-141P I got from Allied Electronics: http://www.alliedele...px?SKU=70218235

 

I used a plastic project box from Radio Shack, I think (don't remember which one). It's 3.5" x 2" X 1.5". It had a prototyping circuit board inside. Then you'll need two 1/4" mono guitar jacks, pretty simple, really.

 

I'm attaching a schematic and some pic's (if this editor will allow it -- seems a bit flakey today...

 

The thing that's strange about your description is that you're using a laptop computer -- apparently plugged into power... You may have a ground loop, but shouldn't. Have you tried using your laptop on battery (not plugged in to external power)? You absolutely wouldn't have a ground loop in that case, but if you try and still do, an isolation transformer won't help that... I'm curious if going on battery helps. If it does, then the isolation transformer will help when your laptop is plugged in...

 

Dave

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