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[Solved] Ground Loop Noise Identified. Balanced Connection Wanted. What Is the Best Solution for Me?

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#1
Background
I've identified what I think is a ground loop. I can hear a buzzing sound and noise. I've managed to reduce the noise significantly by using different ports, outlets, and surge protectors. But it is still noticeable with my headphones on high gain.

Setup
Here is my current setup where I've identified what connection causes the noise:
PC -> USB 3 Hub (power + audio) -> Topping D50s -> JDS Atom (High Gain) -> Headphones (M50x, HD599) = No Noise
Add grounded JBL 308P MKII to the JDS Atom in the above using RCA to XLR cables = Noise with Headphones on High Gain, barely perceptible on low gain. No noise in speakers, but there was before I reduced it.

Goals
I would like to both eliminate this ground loop and use balanced cables since I need 10-25ft cables for my JBL 308Ps and LSR310S sub to be placed optimally. I'm looking for a simple solution that will not have any noticeable effect on the audio quality of my 308Ps or any future upgrade. I would prefer to keep my D50s instead of buying something like a SMSL SU-8. I think i've also read somewhere on ASR that the JBL 305 perform better and have less hiss with a balanced connection and over 2Vrms.

Solution?
From what I've learned, a passive isolator like this should do what I want:
https://www.amazon.ca/dp/B00BSY3FP4/ | https://www.radialeng.com/product/stagebug-sb6

Any other suggestions?

Some newb questions:
With a passive isolator that converts to balanced, would the levels on the JBL need to be set to +4dBu instead of -10dBV? Did some Googling, and afaik it should be set to +4dBu in my case with or without the isolator. Also see below.
Does the passive isolator change the Vrms going to the JBL? Shouldn't (SB-6 doesn't because it's a unity gain device)
 
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OP
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Thread Starter #3
My new PC was making noise on my DX3 Pro. So I disconnected its USB connection and used toslink from the motherboard. Problem solved. :)
I tried that, but the main source of the ground loop noise seems to be the USB power going in to the D50s. The USB data connection has far less noise on it's own.

This solution also doesn't help with needing 15-20ft cables which i'm worried will introduce noise if it's not balanced.
 

Matias

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#4
Remove the ground from the JBL 308P MKII? Cheater plug or just open the receptacle and disconnect it.
 
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Thread Starter #5
Remove the ground from the JBL 308P MKII? Cheater plug or just open the receptacle and disconnect it.
Do you mean to test? Because i'm already fairly certain the JBL 308P is the source of the ground loop since the noise occurs as soon as I plug in the power to it even if it and the D50s are turned off.
If you meant permanently, i'd rather be safe and not do that.
 

Matias

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#6
I am no expert, but some AVRs don't have ground pin at all, so I don't know how unsafe that is.

Or just plug them in and out every time you listen to them hehe. :)
 
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Thread Starter #7
I am no expert, but some AVRs don't have ground pin at all, so I don't know how unsafe that is.

Or just plug them in and out every time you listen to them hehe. :)
Every place I read about ground loops suggested not to remove the ground permanently for safety reasons. Many DACs and HP Amps don't have a ground though as you've noticed.

I could unplug my speakers every time, and I considered it at first. But i'd hate doing that and would rather use another solution if it exists, even if it costs money. That also doesn't give me a balanced connection for the 15-20ft XLR cables I will run.
 

Berwhale

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#8
Can you characterise the noise? Is it a buzzing or a hiss? You will get hiss (high pitched white noise) from many active monitors including the JBL's. I have this on my little JBL 1 Series 104's, but it's only noticeable at very high volumes (on the speakers) when there is nothing playing. I had buzzing on the 104's recently at much lower volumes that was really bugging me until I realised that i'd moved a cordless digital phone (DECT) base station right next to the right hand speaker (the one with the amp in). I moved the phone a couple of feet away and the buzzing disappeared. I also moved an Echo Dot away from the speaker, although it wasn't causing any audible issues.
 
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Thread Starter #9
Can you characterise the noise? Is it a buzzing or a hiss? You will get hiss (high pitched white noise) from many active monitors including the JBL's. I have this on my little JBL 1 Series 104's, but it's only noticeable at very high volumes (on the speakers) when there is nothing playing. I had buzzing on the 104's recently at much lower volumes that was really bugging me until I realised that i'd moved a cordless digital phone (DECT) base station right next to the right hand speaker (the one with the amp in). I moved the phone a couple of feet away and the buzzing disappeared. I also moved an Echo Dot away from the speaker, although it wasn't causing any audible issues.
It's a buzzing sound. I only hear it through my headphones as the hiss of the JBLs drowns out the buzzing. I'll see if I can get a recording of it, but it's very quiet.

The only things near my DAC and amp are my computer monitors, external HHDs 10-12in away, keyboard mouse etc.

I tried using my USB battery to power the D50s, and that seems to have eliminated the noise that was coming from the power cable which was the main source. The noise from the USB data cable remained, and of course that could removed with optical.
I've tried connecting the D50s power and data directly to my computer, no noticeable difference.
Keep in mind the noise only occurs when my speakers are connected to the amp and outlet (ground).


I'd much prefer buying something like the isolator I linked than spending so much time troubleshooting the issue and having things connected just right. Assuming it should have no audible effect on the sound quality. I'd also get the benefit of balanced. So if anyone has another simple solution like that, please let me know.
 
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g29

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#10
FWIW, I had a slight ground loop with a single ended USB DAC (PC -> USB DAC-> XO -> Amps -> Speakers).

I made a USB ground block cable from spare parts and a cell phone charger. No more hum. Broke shield ground and offloaded the +/- power lines to the 2-prong cell phone charger.
 
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Thread Starter #11
FWIW, I had a slight ground loop with a single ended USB DAC (PC -> USB DAC-> XO -> Amps -> Speakers).

I made a USB ground block cable from spare parts and a cell phone charger. No more hum. Broke shield ground and offloaded the +/- power lines to the cell phone charger.
I could fix the ground loop from the USB -> DAC side too. Still wouldn't give me balanced, but it's a start.

Any simple solution for isolating the USB side that outweighs the cost/benefit of the isolator for the amp -> speaker side?
 

g29

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#12
I could fix the ground loop from the USB -> DAC side too. Still wouldn't give me balanced, but it's a start.

Any simple solution for isolating the USB side that outweighs the cost/benefit of the isolator for the amp -> speaker side?
According to posts on ASR, transformers solutions appear to have their own noise issues including the spendy Jensen transformers.
 
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Thread Starter #13
According to posts on ASR, transformers solutions appear to have their own noise issues including the spendy Jensen transformers.
Well if it fixes the noise in my headphones while not adding any noticeable noise to the speakers compared to their hiss, then I think it's worth giving it a try a returning it if i'm not happy. At that point I may just come up with a really easy way to disconnect my speakers whenever I use my headphones.
 

MRC01

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#14
Debugging and solving grounding problems can get tricky.

I don't think using a cheater plug is all that dangerous. Some headphone amps and preamps have a "ground lift" switch that essentially does the same thing.

When I built a stepped attenuator, and a phono headamp, both unbalanced, I encountered ground loops that asymmetric grounding eliminated. That is, I connected one channel's (L or R, doesn't matter) signal ground to earth ground, but not the other.
 
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#15
Just because some equipment does not have a ground pin, does NOT mean it is safe to remove it from equipment that does have one. There are electrical safety codes for different classes of equipment, and it needs to comply with the double-insulation rules before it can be run without the ground wire it came with.
 

pwjazz

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#16
I had the same issue and added a Focusrite Scarlett Solo to use as a preamp for my powered monitors. Problem solved, and I have a nice little audio interface when I want to record from a proper mic or instrument.
 
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Thread Starter #17
I had the same issue and added a Focusrite Scarlett Solo to use as a preamp for my powered monitors. Problem solved, and I have a nice little audio interface when I want to record from a proper mic or instrument.
While that could work for me, I'd be giving up some of the features of my D50s that I use with my speakers. Such as remote control and Bluetooth. But something like that could be an option since i'd sell my Behringer UMC22 and upgrade to that. I assume i'd get the same results with a SMSL SU-8 balanced DAC too. I'll think about it.
 

vavan

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#18
Every place I read about ground loops suggested not to remove the ground permanently for safety reasons
I also suffered from ground loop and ended up isolating ground pin which fixed it for me
 

Berwhale

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#19
Have you tried using RCA to TRS unbalanced cables? The 308 MKII manual states that TRS should be used for connection to consumer kit...

INPUT PANEL
9. XLR INPUT – Connect professional equipment to this connector using a balanced XLR plug.
10. 6MM (¼") INPUT – Connect professional equipment to this connector using a 6mm (¼") balanced plug. Connect consumer equipment to this connector using a 6mm (¼") unbalanced plug.

From: https://adn.harmanpro.com/site_elem.../JBL_3_Series_MkII_Owners_Manual_original.pdf

This would be a relatively cheap thing to try vs. the isolator you link to.
 
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pwjazz

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#20
Have you tried using RCA to TRS unbalanced cables? The 308 MKII manual states that TRS should be used for connection to consumer kit...

INPUT PANEL
9. XLR INPUT – Connect professional equipment to this connector using a balanced XLR plug.
10. 6MM (¼") INPUT – Connect professional equipment to this connector using a 6mm (¼") balanced plug. Connect consumer equipment to this connector using a 6mm (¼") unbalanced plug.

From: https://adn.harmanpro.com/site_elem.../JBL_3_Series_MkII_Owners_Manual_original.pdf

This would be a relatively cheap thing to try vs. the isolator you link to.
That's what I was using when I still had ground loop issues.
 
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