Unbalanced line noise or USB noise? HELP!

edIT · 25th April 2005

I have a Roland Fantom XR that I have hooked into the DI's on the backl of my Pendulum MDP-1A via 21 foot Monster Instrument cables. I get this insane digitized sound almost like there's digital noise running through a sample hold oscillator. I also used to get this when monitoring my MBox off of my Central Station. Whn unplugging my MBox the digital noise went away. The Fantom XR also has a USB port in the back for passing MIDI and i totally thought that was the issue. However after unpluggin it and wiring up good old MIDI cables to the thing I AM STILL GETTING THAT NOISE! Man this is driving me insane. Impedance and unbal vs. bal. signals have always baffled me. What is my problem? Should I just hook the Fantom up Digital via a SPDIF cable, and if so how long can i run a digital cable? Or is there a solution to getting a clean analog signal?

edIT · 25th April 2005

edIT · 26th April 2005

can anyone help out?

aloiv2 · 26th April 2005

i had a similar problem when using my soundblaster extigy as an A/D converter while my laptop was plugged in. now i have to do all of my recording running off of battery power.
i haven't found an answer to fixing it, the only explnation i could come up with was that the audio ground, and the comuter's digital ground were interfering, and i was getting the same digital sound.
while i haven't gotten to play with sample hold oscillators too much, i can describe the sound:
there is a high pitched center to it, but it cuts out every once in a while depending on the hard drive activity and processor activity.
i assume that the audio in my extigy is being grounded through the shield on the USB cable.
i've experimented with a few USB cables, trying to ground lift them and test them with the system, didn't work. i think the real solution would be to figure out how to ground lift the USB cable, while providing a dedicated ground to the external box, but this is something i flat out haven't had the time to try yet.
-alex

TheToxicBarmaid · 26th April 2005

It's to do with your earthing- alot of laptops/desktops with TFT screens suffer from it. You need to remove the earth from your computer which should fix it for you. There are these little plug adaptors that you can get- i picked up mine on A BA flight out the Italy once- they convert anywhere to anywhere else but remove the earth pin- thats what I use. Alternatively you can PTFE tape up the earth pin- not ideal- or get a multi-way that you've removed it from- again- not the best way but it'll cure your noise thing...

aloiv2 · 27th April 2005

it sounds like you are talking about preventing ground loop issues (perhaps the earthing of which you speak?). i have used ground lift plugs as well, to no avail with my equipment.

aloiv2 · 27th April 2005

i'd be interested to see if anyone has any further insight into this.

i've noticed it only happens with some brands: HP, Dell. and not with others: Mac, Sony.

does anyone know if it's possible to re-ground equipment such as this?
-alex

25th April 2005	#1
edIT Gear addict Join Date: Jun 2004 Location: Los Angeles Posts: 393 Thread Starter	Unbalanced line noise or USB noise? HELP! I have a Roland Fantom XR that I have hooked into the DI's on the backl of my Pendulum MDP-1A via 21 foot Monster Instrument cables. I get this insane digitized sound almost like there's digital noise running through a sample hold oscillator. I also used to get this when monitoring my MBox off of my Central Station. Whn unplugging my MBox the digital noise went away. The Fantom XR also has a USB port in the back for passing MIDI and i totally thought that was the issue. However after unpluggin it and wiring up good old MIDI cables to the thing I AM STILL GETTING THAT NOISE! Man this is driving me insane. Impedance and unbal vs. bal. signals have always baffled me. What is my problem? Should I just hook the Fantom up Digital via a SPDIF cable, and if so how long can i run a digital cable? Or is there a solution to getting a clean analog signal? __________________ edIT (The Glitch Mob, Alpha Pup, Planet-Mu) http://www.facebook.com/edITmusic http://www.facebook.com/theglitchmobmusic

25th April 2005	#2
edIT Gear addict Join Date: Jun 2004 Location: Los Angeles Posts: 393 Thread Starter	bump

26th April 2005	#4
aloiv2 Gear interested Join Date: Apr 2005 Location: new york Posts: 7	my experience i had a similar problem when using my soundblaster extigy as an A/D converter while my laptop was plugged in. now i have to do all of my recording running off of battery power. i haven't found an answer to fixing it, the only explnation i could come up with was that the audio ground, and the comuter's digital ground were interfering, and i was getting the same digital sound. while i haven't gotten to play with sample hold oscillators too much, i can describe the sound: there is a high pitched center to it, but it cuts out every once in a while depending on the hard drive activity and processor activity. i assume that the audio in my extigy is being grounded through the shield on the USB cable. i've experimented with a few USB cables, trying to ground lift them and test them with the system, didn't work. i think the real solution would be to figure out how to ground lift the USB cable, while providing a dedicated ground to the external box, but this is something i flat out haven't had the time to try yet. -alex

27th April 2005	#6
aloiv2 Gear interested Join Date: Apr 2005 Location: new york Posts: 7	ground loop perhaps? it sounds like you are talking about preventing ground loop issues (perhaps the earthing of which you speak?). i have used ground lift plugs as well, to no avail with my equipment.

27th April 2005	#7
aloiv2 Gear interested Join Date: Apr 2005 Location: new york Posts: 7	i'd like to keep this thread going. i'd be interested to see if anyone has any further insight into this. i've noticed it only happens with some brands: HP, Dell. and not with others: Mac, Sony. does anyone know if it's possible to re-ground equipment such as this? -alex

26th April 2005	#5
TheToxicBarmaid Gear interested Join Date: Apr 2005 Posts: 1	It's to do with your earthing- alot of laptops/desktops with TFT screens suffer from it. You need to remove the earth from your computer which should fix it for you. There are these little plug adaptors that you can get- i picked up mine on A BA flight out the Italy once- they convert anywhere to anywhere else but remove the earth pin- thats what I use. Alternatively you can PTFE tape up the earth pin- not ideal- or get a multi-way that you've removed it from- again- not the best way but it'll cure your noise thing...

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