Weird hum issue, can be cut via USB

[cassianoleal]

Hi Helix community!

 

I have a very strange (to me) issue with what sounds exactly like ground hum (and probably is). I have isolated the problem as best as I can but I still don't know how to properly solve it.

 

Here's the most basic setup where I can reproduce the issue:

Electric installation: mains socket -> power strip (where speakers are powered from) -> power strip (where the Helix is plugged). I live in the UK and everything is grounded, and in theory to the same ground since they are all connected to the same mains socket.

 

Only thing plugger to the Helix are 2 KRK Rokit 5 speakers via XLR.

 

As soon as I switch the Helix on, I get the ground hum coming out of the speakers. It happens even with volume turned to 0, and doesn't ever increase in volume regardless of output level. If I disconnect the XLR cables from the Helix, it goes away, so it's definitely something between the Helix and the speakers.

 

At this point, with the hum going, I connect the USB cable to the Helix. Nothing changes. As soon as I connect the other end of the USB cable to my old 13" Macbook Pro, the hum goes away completely. It makes no difference whether the Macbook charger is connected or not.

 

Adding another layer to the weirdness. I have a newer USB-C Macbook Pro, and to use the Helix with it I connect it to a USB-C hub (https://www.amazon.co.uk/HyperDrive-Type-C-Adapter-50Gbps-MacBook-DUO-7-2-GREY/dp/B07DFG6TCG/ref=sr_1_1_sspa?keywords=hyperdrive&qid=1557237156&s=gateway&sr=8-1-spons&psc=1). Now, if I plug the Helix's cable to the hub the hum also stops even if the hub is not connected to anything, not even the computer. So just a floating USB hub connected to the Helix makes the hum stop.

 

Another one: I have some small USB-B to USB-C adaptors that I use to plug stuff to the Mac. If I plug one of those to the cable (again, even when disconnected from the computer) the hum amplifies.

I don't know what's happening or how to solve it. Right now I'm just keeping the Helix plugged to one of these miraculous hum-cutting pieces of equipment (USB hub or older Mac) but I'd love to resolve the issue independently of the USB cable being plugged to the Helix.

Any ideas or possible explanations?

Thanks!

[macelind]

I cannot explain what you are experiencing but I can tell you I experienced a similar issue when using my KRK Rokit 5 monitors.

With the USB cable from my HX Stomp connected to my laptop, I experienced overpowering hum and noise. Once I disconnected the USB cable, the noise disappeared.

I do not experience this noise issue when when I use my powered PA speakers instead of the KRK monitors.

My best guess is the KRK monitors are more sensitive to ground loop issues.

[njglover]

Not exactly sure why it behaves quite like that, but ground loops are weird things. Have you tried messing with the ground switch on the back of the Helix? That would isolate the ground going to the KRKs from the rest of the circuit and could help.

[cassianoleal]

7 hours ago, macelind said:

With the USB cable from my HX Stomp connected to my laptop, I experienced overpowering hum and noise. Once I disconnected the USB cable, the noise disappeared.

 

I can understand that. You're creating a ground loop between the laptop and the HX Stomp.

In my case I seem to be cutting a ground loop by connecting the USB to certain devices, amplifying by connecting to others, regardless of whether those are grounded or not, plugged in or not, or even receiving any kind of electric current. ¯\_(ツ)_/¯

[cassianoleal]

1 hour ago, njglover said:

Have you tried messing with the ground switch on the back of the Helix?

 

I have. It makes zero difference unfortunately...

[cassianoleal]

Oh well... Just in case someone else comes here with a similar problem, I've "fixed" it by adding yet another gizmo to the setup: https://www.amazon.co.uk/gp/product/B01N3XKOLG

 

Now when I connect the Helix to my USB-C laptop I have Helix -> USB cable -> Ground Loop Eliminator -> USB-A to USB-C adaptor -> computer.

 

Expensive gizmo as well but at least it works and seems to have helped with the driver loading correctly after unplugging it and then plugging it again - it would not work the second time, now it seems fine.

[macelind]

15 hours ago, cassianoleal said:

 

I can understand that. You're creating a ground loop between the laptop and the HX Stomp.
 

 

Yes sir, a ground loop is what I believe I experienced but, my point was and is, I only experienced it with my KRK monitors. I connected everything in the same manner when using my powered PA speakers and the did not experience the ground loop noise. 

 

At any rate, I am glad you have found a solution for your issue and it may be a solution for me as well.

 

Thank you, sir!

[cassianoleal]

Oh yeah, I didn't mean to dismiss your comment - sorry if it came across as that.

Every bit of info is useful really, and you might be correct about the KRKs (unfortunately I can't test it with a different set of speakers right now).
 

Thanks!

[macelind]

6 hours ago, cassianoleal said:

Oh yeah, I didn't mean to dismiss your comment - sorry if it came across as that.

Every bit of info is useful really, and you might be correct about the KRKs (unfortunately I can't test it with a different set of speakers right now).
 

Thanks!

 

Not at all, sir. I thought maybe I should clarify my previous statement. My intent is to use the KRKs for monitoring eventually so, your solution is of interest to me!

 

Thank you!

[HonestOpinion]

On 5/7/2019 at 9:57 AM, cassianoleal said:

Hi Helix community!

 

I have a very strange (to me) issue with what sounds exactly like ground hum (and probably is). I have isolated the problem as best as I can but I still don't know how to properly solve it.

 

Here's the most basic setup where I can reproduce the issue:

Electric installation: mains socket -> power strip (where speakers are powered from) -> power strip (where the Helix is plugged). I live in the UK and everything is grounded, and in theory to the same ground since they are all connected to the same mains socket.

 

Only thing plugger to the Helix are 2 KRK Rokit 5 speakers via XLR.

 

As soon as I switch the Helix on, I get the ground hum coming out of the speakers. It happens even with volume turned to 0, and doesn't ever increase in volume regardless of output level. If I disconnect the XLR cables from the Helix, it goes away, so it's definitely something between the Helix and the speakers.

 

At this point, with the hum going, I connect the USB cable to the Helix. Nothing changes. As soon as I connect the other end of the USB cable to my old 13" Macbook Pro, the hum goes away completely. It makes no difference whether the Macbook charger is connected or not.

 

Adding another layer to the weirdness. I have a newer USB-C Macbook Pro, and to use the Helix with it I connect it to a USB-C hub (https://www.amazon.co.uk/HyperDrive-Type-C-Adapter-50Gbps-MacBook-DUO-7-2-GREY/dp/B07DFG6TCG/ref=sr_1_1_sspa?keywords=hyperdrive&qid=1557237156&s=gateway&sr=8-1-spons&psc=1). Now, if I plug the Helix's cable to the hub the hum also stops even if the hub is not connected to anything, not even the computer. So just a floating USB hub connected to the Helix makes the hum stop.

 

Another one: I have some small USB-B to USB-C adaptors that I use to plug stuff to the Mac. If I plug one of those to the cable (again, even when disconnected from the computer) the hum amplifies.

I don't know what's happening or how to solve it. Right now I'm just keeping the Helix plugged to one of these miraculous hum-cutting pieces of equipment (USB hub or older Mac) but I'd love to resolve the issue independently of the USB cable being plugged to the Helix.

Any ideas or possible explanations?

Thanks!

 

You may have already tried this but try plugging in and mixing and matching devices split across two different outlets/circuits. 

[zolko60]

I can confirm that Helix acts just opposite to my other USB powered interfaces.
It seems to "ground" or "shield" my guitar enviroment via USB cable so the computer/laptop power supply interference is silenced. Playing with Hellix LT USB connected and disconnected with a the computer or laptop near by is the different experience. What i write about is the headphone listening, connecting monitors causes plenty of different nature issues.