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PC sound in signal path

Postby Leftyjay » Sat Aug 17, 2019 2:47 pm

Hi !
I've switched to a PC only guitar rig recently for various of reasons (new pc, eleven rack doesnt cut it anymore, playing only at home, etc).

Thing is, I get an anoying sound in the signal path which is most likely pc interference. See the video below.

https://youtu.be/wDnIjjBqMK0

Here's a few important things to know :

* signal path description : LTD Gary Holt signature guitar with EMGs --> Eleven Rack (as audio interface) --> pc via USB --> (from 11R output) Atomic amp.

* PC is brand new, I7, ssd disks only, 32g of ram, the works

* I can dial out that annoying sound when playing through the headphones. The noise remains persistant through the Atomic. I even tried to put a decimator between the output of the 11R and the Atomic, without any success.

* the sound goes away completely if playing only through the 11R and the PC is shutdown.

What are your thoughts?
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Re: PC sound in signal path

Postby Wonks » Sat Aug 17, 2019 3:08 pm

Sounds quite digital so probably a ground loop situation. You've got three items all separately grounded - the 11 rack, the computer and the amp. with cables running between them.

The Decimator is an expander/noise gate, so won't he;p here as the noise is generated somewhere between the 11 Rack, the PC and the Atomic amp.

First of all, are all the items powered from the same multi-way power board? if not, try that as that will minimise the ground loop path.

If that doesn't work, I'd suggest buying an ART Hum eliminator https://www.gak.co.uk/en/art-dti/781?gc ... lsrc=aw.ds, and put that between the 11 rack and the Atomic amp. That will break one of the ground loop paths.

If you still have noise, then you'll probably need to get a USB ground loop isolator - though you may be better off with a small USB powered audio interface, instead of the 11 rack, that has an instrument (high impedance) input, as that breaks one of your ground paths as there's no mains power supply to it.
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Re: PC sound in signal path

Postby Leftyjay » Sat Aug 17, 2019 3:38 pm

Wonks wrote:Sounds quite digital so probably a ground loop situation. You've got three items all separately grounded - the 11 rack, the computer and the amp. with cables running between them.

The Decimator is an expander/noise gate, so won't he;p here as the noise is generated somewhere between the 11 Rack, the PC and the Atomic amp.

First of all, are all the items powered from the same multi-way power board? if not, try that as that will minimise the ground loop path.

If that doesn't work, I'd suggest buying an ART Hum eliminator https://www.gak.co.uk/en/art-dti/781?gc ... lsrc=aw.ds, and put that between the 11 rack and the Atomic amp. That will break one of the ground loop paths.

If you still have noise, then you'll probably need to get a USB ground loop isolator - though you may be better off with a small USB powered audio interface, instead of the 11 rack, that has an instrument (high impedance) input, as that breaks one of your ground paths as there's no mains power supply to it.

Atomic and 11R are connected to my Furman powerbar, than to another regular power bar (i need to buy an extension...). Pc is connected to the latest only so it doesnt shutdown when turning of the Furman. How should I connect all of that to try to avoid that ground loop?
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Re: PC sound in signal path

Postby Wonks » Sat Aug 17, 2019 4:01 pm

Just try temporarily feeding them all from the first powerbar, and see if that improves matters, but as they are all fed from the same power socket, any ground loop paths will be small it, so it's unlikely that it will solve anything. So it's then down to isolators on the signal cables.
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Re: PC sound in signal path

Postby Leftyjay » Sat Aug 17, 2019 4:03 pm

Wonks wrote:Just try temporarily feeding them all from the first powerbar, and see if that improves matters, but as they are all fed from the same power socket, any ground loop paths will be small it, so it's unlikely that it will solve anything. So it's then down to isolators on the signal cables.

Isolators on the signal cables? So basically I shoud just buy something like the ART?
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Re: PC sound in signal path

Postby Martin Walker » Sat Aug 17, 2019 5:01 pm

Leftyjay wrote:Isolators on the signal cables? So basically I shoud just buy something like the ART?

Essentially yes, and that's probably the easiest solution.

However, it's often possible to resolve ground loops by using balanced inputs and output if you have them available, rather than unbalanced ones, or sometimes simply snipping the earth connection on one or more of your unbalanced signal cables just before the destination end to break the loop.


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Re: PC sound in signal path

Postby Leftyjay » Sat Aug 17, 2019 5:24 pm

So if im correct, I just need to place the ART hum eliminator between my guitar and audio interface ?
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Re: PC sound in signal path

Postby rabidhamster » Sat Aug 17, 2019 6:18 pm

You may as well try and see if that works for you but odds are it wont. Typical PCs have very noisy fans, and you may even still have a magnetic spinning hard drive, which introduce a lot of interference when running, which has to be anytime the PC is running.

Lots of people keep their PC as far away from their recording area as possible to help avoid. A big problem is using an internal sound card in your PC - it has 0 shielding against the interference your computer puts out. Your guitar pickups may also be picking up this interference if you're close enough to your PC while its running, happens to me recording externally when a desktop PC is near enough.
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Re: PC sound in signal path

Postby Wonks » Sat Aug 17, 2019 6:59 pm

No internal soundcard as the 11 Rack is being used as an external audio interface. No balanced cables as the 11 rack outputs are feeding an Atomic (Reactor I assume) Full range combo amp and reading the manual, it only appears to have unbalanced TS inputs.
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Re: PC sound in signal path

Postby James Perrett » Sat Aug 17, 2019 8:12 pm

Leftyjay wrote:So if im correct, I just need to place the ART hum eliminator between my guitar and audio interface ?

No - between the 11 rack and the Atomic (as Wonks said in a previous post).
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Re: PC sound in signal path

Postby Leftyjay » Sat Aug 17, 2019 8:31 pm

James Perrett wrote:
Leftyjay wrote:So if im correct, I just need to place the ART hum eliminator between my guitar and audio interface ?

No - between the 11 rack and the Atomic (as Wonks said in a previous post).

Thing is, i hear that sound through the headphones plugged in the 11r. Putting the hum elimanator between the 11r and the Atomic won't do anything. Sure, i can dial out that noise with some heavy noise gate within the vst...
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Re: PC sound in signal path

Postby Wonks » Sat Aug 17, 2019 9:42 pm

The ART box simply breaks the physical ground connection between the 11 rack and the Atomic amp. That's how it stops that particular ground loop.

The 11 rack is designed to connect to a PC so it shouldn't create a ground loop problem on its own, so it's probably the extra connection to the amp that are causing the loop.

It's the multiple ground paths that cause noise issues with digital equipment. So you remove the multiple paths and the ground loop noise (created in the 11 rack) stops.
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Re: PC sound in signal path

Postby Leftyjay » Sat Aug 17, 2019 10:07 pm

Even if the Atomic amp is off? I mostly play through headphones, with the Atomic amp at off.

Fyi, in the video, theres no noise created by the pups themselves since I moved far away enough for that noise to go away
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Re: PC sound in signal path

Postby Wonks » Sat Aug 17, 2019 10:13 pm

Leftyjay wrote:Even if the Atomic amp is off? I mostly play through headphones, with the Atomic amp at off.

The ground path is still there if the amp is still plugged in (it's partly a safety feature and partly how the amp works) and there's a signal lead between the 11 rack and the amp. But lack of any active electronics in the amp will probably make things quieter when off than when it is on.
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Re: PC sound in signal path

Postby CS70 » Sat Aug 17, 2019 10:13 pm

Hm that sounds a bit like radio frequency noise? Like when in old times, you heard an sms arriving in the amp before it got to the phone?

If the PC emits RF, it could just get into your guitar cable or pickups - and it would make perfect sense that with the PC off you don't hear it.

You could make a quick test leaving the PC on and all in the same position, but disconnected to the 11r - and play the latter as a standalone unit. Try also have someone moving the mouse (is it wirless) or so.
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Re: PC sound in signal path

Postby Leftyjay » Sat Aug 17, 2019 10:17 pm

CS70 wrote:Hm that sounds a bit like radio frequency noise? Like when in old times, you heard an sms arriving in the amp before it got to the phone?

If the PC emits RF, it could just get into your guitar cable or pickups - and it would make perfect sense that with the PC off you don't hear it.

You could make a quick test leaving the PC on and all in the same position, but disconnected to the 11r - and play the latter as a standalone unit. Try also have someone moving the mouse (is it wirless) or so.

Maybe i wasnt clear on my issue, but as soon as the pc is off and i play through the 11r, the noise goes away. When the pc is working hard (cpu fan works more) it increases the noise. To me, its obvious that the problem is coming from the pc. Is how to get rid of it the problem :)
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Re: PC sound in signal path

Postby Wonks » Sat Aug 17, 2019 10:18 pm

EMGs are pretty damn quiet though and there's a fair amount of noise there.

Have you changed the guitar battery recently? If not, worth trying out a new one, in case reduced voltage is allowing more noise to be picked up.
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Re: PC sound in signal path

Postby CS70 » Sat Aug 17, 2019 10:21 pm

Leftyjay wrote:
Maybe i wasnt clear on my issue, but as soon as the pc is off and i play through the 11r, the noise goes away. When the pc is working hard (cpu fan works more) it increases the noise. To me, its obvious that the problem is coming from the pc. Is how to get rid of it the problem :)

Yeah, what I meant is that it may not be a ground loop at all but a strong RF emission from the PC instead (is it self built?). They both would generate noise which might stop with the PC unpowered , but the remedy for the latter is very different than the one for the former.
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Re: PC sound in signal path

Postby Leftyjay » Sat Aug 17, 2019 10:32 pm

CS70 wrote:
Leftyjay wrote:
Maybe i wasnt clear on my issue, but as soon as the pc is off and i play through the 11r, the noise goes away. When the pc is working hard (cpu fan works more) it increases the noise. To me, its obvious that the problem is coming from the pc. Is how to get rid of it the problem :)

Yeah, what I meant is that it may not be a ground loop at all but a strong RF emission from the PC instead (is it self built?). They both would generate noise which might stop with the PC unpowered , but the remedy for the latter is very different than the one for the former.

Self built indeed. I think, if we are going that route, is important to know that both side of the pc is closed with tempered glass (and not steel or something similar). Furthermore, as I'm typing, if I move the mouse around (WIRED mouse), I can hear a variation of the artifact that I hear in the signal. For some reason, the noise gate within BIAS FX2 (or any other VSTs) is blocking that artifact if I'm playing with my headphones, but will go through the Atomic, even with all VSTs closed.
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Re: PC sound in signal path

Postby James Perrett » Sat Aug 17, 2019 10:49 pm

Leftyjay wrote:Self built indeed. I think, if we are going that route, is important to know that both side of the pc is closed with tempered glass (and not steel or something similar).

It may look pretty but that certainly isn't going to help create a noise free studio. You need a decent metal enclosure all around with all the panels properly grounded so that no electromagnetic fields can leak out. A large expanse of glass on either side is likely to let all kinds of nasty signals out into the studio.
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