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Loud Hum with Helix Stomp

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My travel rig is a Helix Stomp into a Tech 21 Power Engine - sounds great.

 

However, I recently added a Line 6 G70 wireless unit to the mix, and when I plug the Stomp and G70 power adapters into the same conditioned power strip, or even the same circuit in the room, I get a very loud hum/buzz through the Power Engine.

 

I then disconnected the G70 and tried using a Ditto looper (powered by a One-Spot adapter) and got the same loud hum/buzz.


However, using a Helix LT with the G70 or Ditto works/sounds fine, so the issue seems to be with the Helix power supply.

 

Any ideas?

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I had the same issue with the HX Stomp connected to... pretty much anything.... except when I plugged it into my computer. Apparently, the 2-prong US power adapter is not grounded, so the only way to stop the madness is to ground the HX Stomp either via a PC or by replacing the power supply with a grounded one. I actually took the power supply apart and moved it to a newer bigger case and added a 3-prong power cable with the ground pin (the third, round pin) going through a switch so that I could either ground the HX Stomp (when not connected to a PC) or lift it (when connected to a PC).  I wouldn't recommend this, unless you are knowledgeable in working with power supplies, as the board inside is very small and crammed and one side is connected directly to 120V.

 

One alternate solution, which is far safer and I tried it before deciding to mod the power supply would be to take a spare similar USB cable (not the one that came with the the HX Stomp, obviously) and cutting it near the end opposite the HX Stomp, peeling off the plastic sleeve to expose the metal braid and attaching it to the (usually the middle) screw that holds the wall power outlet in place. This *must* be ground, as per the US electrical code. Once you have that, when you plug the other end of the cable into the HX stomp, you are grounding it, without the need to plug the USB cable into a PC. Just make sure that none of the 4 wires inside the USB cable are touching the metal braid or each other. The wires are usually colored red, black, green and white. Red and black are USB power and ground, respectively and green and white are USB data.

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awesome, thanks deadlocked! Glad to know it isn't just me, and great information!

 

Since I'm not the handiest with electronics, I'll check the specs/power on the adapter and see if there's an aftermarket adapter that's grounded that supplies the correct power.

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The HX Stomp uses a non-standard 9V plug. Though you may be able to find a 9V 3A (or better) power supply for it, I think only a handful of them would fit the HX Stomp. Polarity is also crucial, if you get one that has reverse polarity, at best it won't work and at worst, it might damage something inside the HX Stomp. Without opening it, I am not sure whether it has a protection diode or something else that would prevent a wrong polarity power supply from frying the unit.

 

If you have a 5v USB charger with a  3-prong (grounded) power cable, you may also try to plug the USB cable that came with the HXS into it while the charger plugged into the outlet. the HXS will NOT power from it, you are basically only using the ground on it. If your 5V charger only has a 2-prong power cable, it will almost certainly NOT work, you need the ground pin to make the hum go away.

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super helpful, thanks again deadlocked!

 

Looking at Amazon, I see some grounded power strips that also provide USB power... that might work.

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You're welcome.

 

Give it a try. If what you are experiencing is a grounding issue, plugging the USB cable from the Helix into the USB strip should help with the hum levels, as long as the power strip grounds the USB ports appropriately.

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well, that didn't help. I don't know if the USB ports are connected to the overall grounding of the power strip, but plugging in the Helix (via USB) to the USB port on the power strip made the hum even worse. 

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hmm... maybe the USB ports do not share the ground with the power strip? That would be odd, though not impossible. Also, if possible, did you try to reverse the HX Stomp power supply on the power outlet? I.e. if the brick is facing left, try facing right, or vice-versa. When I opened mine, there was a white wire (neutral) and a black wire (live). maybe reversing the way the brick is plugged into the outlet might help? Or try connecting the HX Stomp to a computer using the USB cable, just for testing purposes. If the hum goes away or reduces significantly, then you know you have a grounding issue somewhere. The computer would have to be a "desktop" model, with a 3-prong power supply cable or a laptop with a charger that is also grounded, a laptop with a 2-prong charger would not be truly grounded and therefore, it would not help.

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thanks again deadlocked. I too thought it would be odd if the USB ports didn't share the grounding of the overall strip. I'll try reversing the Helix Stomp power supply to see if that makes a difference. If that doesn't work, I'll at least test it with a USB going to a grounded PC.

 

(and if you're still in MN, hope you're adversely affected by that deep freeze!)

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Problem appears to be SOLVED!

 

(in fairness, the "problem" was I didn't RTFM.) 

 

I HAD been powering the base unit with a 9V power adapter (yes, of sufficient power for the G70 base unit)

 

However, per the manual, the preferable way to power the unit is via the 5V USB port. Powering the unit via the USB ONLY eliminated the hum.

 

Kudos to deadlocked who got me looking in the right direction!

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Awesome, glad you got your issue sorted out!

 

Yes, I'm in MN, but I kept warm the old fashioned way:

 

Warmest jacket I have, home -> car (heater on) -> work -> car (heater on) -> home   :)  no wandering about for no reason.

 

Looks like your 9V adapter might've been the culprit, as most wall warts aren't grounded properly. Once you plugged it into the 5V USB port on the power strip, then it would be properly grounded and, through the 1/4" cable from the base unit to the LT, the LT would share its ground.

 

so, likely the issue was two power adapters that weren't grounded, therefore having both grounds floating... bad news. Once you grounded the base unit (via USB port on grounded power strip), problem solved.

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