fhludlow

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.com/p/123/pc10k-10k

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.com/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.

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.com/en/content/over_icoupler_usb_isolation/fca.html I bought this, it has the adum3160 chip. http://www.ebay.com/itm/Full-Speed-USB-Isolator-with-Built-in-Full-Power-Transfer-/130884177999?pt=LH_DefaultDomain_0&hash=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.com/Multi-purpose-USB-Isolator-Built-in-DC-DC/dp/B00899UVGW/ref=lh_di_t_dup?ie=UTF8&psc=1&smid=A1PO6NTQYFXQX9 http://www.amazon.com/Firestone-Audio-GreenKey-USB-Isolator/dp/B0074SHH98/ref=pd_sim_sbs_pc_4