GT-100 - "Digital Noise" when connected via 4cm to Amp AND USB

Started by ChrisX, October 07, 2017, 08:06:08 AM

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ChrisX

Hello,

I use my GT-100 in 4cm with tube amps.  Works great.

If I connect the GT-100 to the computer via usb while ALSO having it in 4cm with tube amp, I get a digital background noise.

If I use a notebook computer running from battery, the noise goes away.  This may be some kind of weird ground loop.

First, has anyone else experienced this?

Second, how did you solve it?   My DAW is a desktop computer, I cant record to my Notebook so that option is not good.

I have everything running from same outlet, use hum eliminator to break ground loop, nothing works.  This problem means that I cant use the USB for recording and I can't take advantage of the reamping feature, unless I am just using the built in models and cabs.

rolandvg99

My guess is a ground loop caused by the PC power supply.


PS. What might help is an UPS. Preferably an online one.
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ChrisX

Would I have to run from the UPS battery while recording?

Thanks.

szilard

You can try it and see if it works or fix the ground loop.


ChrisX

The USB cable IS causing the ground loop!!!  An I have no way to isolate ground on a USB cable.

Everything in my studio is powered by Tripp Lite Isolator.  Amps, PC, monitors, GT100.

The GT100 is the bastard step child of the whole system.  Everything is pristene until I connect the GT-100.

The workaround I found for the GT100 (analog outputs) is to put a Hum Eliminator between the GT-100 stereo out, and my computer interface.  Check! That works.

But when I hook the USB cable the similar problem presents and there is no way I can isolate the usb ground.  (The usb noise is more like high pitched whining static or data bursts, the analog out is more like a humming buzzing)

Everything is running from the Trip lite isolator, everything has a common ground. What could this be?




rolandvg99

Common ground does not guarantee a system free of ground loops. There is also noise from certain PSUs that penetrate the Audio chain. A PC with a budget PSU and/or a high performance GPU can and will cause problems. Badly shielded motherboards might also rise problems.


I have a Mackie DL1608 that whines when wired to an i-device. That stock PSU is not great, but using an UPS the whine is gone. That UPS is running from mains, but the isolating circuits inside works wonders. My UPS is a pure sine, line interactive device and my studio is totaly noise free even with VG-99, GP-10 and SY-300 connected using both USB and (un)balanced analog cables.
To V or not to V: That is the question.

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ChrisX

Quote from: rolandvg99 on October 07, 2017, 01:32:09 PM
Common ground does not guarantee a system free of ground loops. There is also noise from certain PSUs that penetrate the Audio chain. A PC with a budget PSU and/or a high performance GPU can and will cause problems. Badly shielded motherboards might also rise problems.


I have a Mackie DL1608 that whines when wired to an i-device. That stock PSU is not great, but using an UPS the whine is gone. That UPS is running from mains, but the isolating circuits inside works wonders. My UPS is a pure sine, line interactive device and my studio is totaly noise free even with VG-99, GP-10 and SY-300 connected using both USB and (un)balanced analog cables.

Thanks, I will try this if the act of physically lifting the ground (3rd pin) from my PC does not work.  In fact, I might get one anyway.


ChrisX


gumtown

Quote from: ChrisX on October 07, 2017, 04:46:59 PM
Thanks, I will try this if the act of physically lifting the ground (3rd pin) from my PC does not work.  In fact, I might get one anyway.
NOT RECOMMENDED REMOVING THE AC POWER EARTH. !!
unplugging the USB cable will cause power arcing at the USB plug,
causing damage to the USB ports on the GT-100 and PC,
and will leave your PC dangerously un-bonded/grounded.

A USB isolator cable is required
https://iftools.com/isolator/isousbcable/index.en.php?gclid=Cj0KCQjw9uHOBRDtARIsALtCa96aXUvFAWaiiqmAoPjEjr06Rn6Bh1r9PUmd2RB6rjVs6ddIBrb-T5EaArGoEALw_wcB

Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

Brak(E)man

Quote from: gumtown on October 07, 2017, 10:02:48 PM
NOT RECOMMENDED REMOVING THE AC POWER EARTH. !!
unplugging the USB cable will cause power arcing at the USB plug,
causing damage to the USB ports on the GT-100 and PC,
and will leave your PC dangerously un-bonded/grounded.

A USB isolator cable is required
https://iftools.com/isolator/isousbcable/index.en.php?gclid=Cj0KCQjw9uHOBRDtARIsALtCa96aXUvFAWaiiqmAoPjEjr06Rn6Bh1r9PUmd2RB6rjVs6ddIBrb-T5EaArGoEALw_wcB



I have a similar problem when my MacBook is plugged in and recording GP
( using only GP as monitor through headphones ) so only two plugged in devices.
I've " solved it " by running the laptop on batteries when recording.
Do you think that a USB cable like that above would be the solution ?
(I don't remember having the same problem with VG 99 using the same MacBook and USB cable.
Not with SY300 either but with a different MacBook )
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GeePeeAxe

I have also too much noise when any USB connection is used with digital instruments, like VG99 and Roland synths. Because the IsoUsb cable costs 119 euro in Germany, I think about other solutions. A port that works with standard 5-pin midi, usb and wireless would be the right solution. Unfortunately Roland has only usb-midi and not standard midi in newer synths and keyboards in the mid-price-range.

ChrisX

Quote from: gumtown on October 07, 2017, 10:02:48 PM
NOT RECOMMENDED REMOVING THE AC POWER EARTH. !!
unplugging the USB cable will cause power arcing at the USB plug,
causing damage to the USB ports on the GT-100 and PC,
and will leave your PC dangerously un-bonded/grounded.

A USB isolator cable is required
https://iftools.com/isolator/isousbcable/index.en.php?gclid=Cj0KCQjw9uHOBRDtARIsALtCa96aXUvFAWaiiqmAoPjEjr06Rn6Bh1r9PUmd2RB6rjVs6ddIBrb-T5EaArGoEALw_wcB



The link someone provided listed cutting the ground as a potential solution.  You should probably remove it from the site.
https://www.vguitarforums.com/smf/index.php?topic=367.0

Amazon has many reasonably priced USB isolators.  I may try this one for $35

https://www.amazon.com/SMAKN-Isolator-Digital-Isolation-Industrial/dp/B00XXPO4UG/ref=sr_1_3?ie=UTF8&qid=1507472922&sr=8-3&keywords=usb+isolator

ChrisX

Linked device (above) does not work.  It cleans up the noise, but the software cannot identify that teh GT is connected.  However, the device works with mouse.  There might be a device of this type that actually works.

admin

#15
Quote from: ChrisX on October 10, 2017, 11:25:33 AM
Linked device (above) does not work.  It cleans up the noise, but the software cannot identify that teh GT is connected.  However, the device works with mouse.  There might be a device of this type that actually works.

need to

A ) use a USB galvanic  Isolator that supports USB 2.0 @ 480mbps
https://hifimediy.com/high-speed-usb-isolator-480Mbps

or

B) use a laptop PC on battery power.