Ground Looped

[CharlieC]

About a year ago, I purchased a backup 9V power supply for my Zoom B3 and Zoom MS-60B pedals, a Godlyke Power-All PA-9.

The product's specs, build quality, and price point made my purchase of one a no-brainer. Following some basic testing and light usage, I relegated this backup power supply to my band rehearsal space, never really going further with it, as it was simply a backup to the Zoom AD-16 adapter included with the Zoom B3.

Out of convenience recently, I grabbed the Power-All PA-9 instead of the Zoom AD-16 to power the Zoom B3 for a round of high-scrutiny, cabinet testing. To my disbelief, I discovered a ground loop hum hiding low in the signal. My plans for cabinet testing quickly took back-seat to this new-found ground loop issue.

{ a ground loop causes an annoying hum heard when not playing }

My signal chain was P-Bass, to Zoom B3, to Aguilar Tone Hammer 500.

I tried switching basses, cables, amps, power-outlets, etc. to no avail until I replaced the Power-All with Zoom's adapter. Bingo!

I then tried an old BOSS PSA-120 adapter with no issue.

I then swapped the Zoom B3 for the similar Zoom MS-60B with no issue until I re-connected the Power-All.

A visit to Godlyke's web site then resulted in my further disappointment.

Contained in the [Invalid or Expired Link Removed] was a paragraph on this very issue, which is caused specifically by having both the amp and the power supply on the same AC circuit!

In my gigging world, a single AC circuit is all one can hope to expect and unfortunately I now cannot rely on the Power-All unit due to this unrealistic prerequisite.

I do not have plans to contact Godlyke at this time, since they openly acknowledge the potential for this issue and the likely cause of it in their documentation. I am certain that many satisfied customers do exist, and until recently, I was one of them.

Cheers!

 

[CharlieC]

This seems to me an unrealistic prerequisite for gigging musicians:

 

[bongomania]

Was there anything else plugged in to the Godlyke supply at the same time? Or was the one effect unit the only thing on that supply? Were there any extra daisy chain plugs uncovered, exposed, that could have been touching a metal surface?

The reason I ask all this is because using the Powerall by itself is exactly like using a Boss wall wart or a Zoom wall wart by itself, as far as ground loops are concerned. The Powerall does not have a special vulnerability to ground loops that the others do not have.

Now, there are other reasons why you might have gotten a hum. It could have been a bad connection with one of the Powerall's wires or jacks. The supply itself might have been faulty, e.g. with a poor ground connection internally. Or there might have been something external like an exposed plug touching a metal pedal or pedalboard.

 

[CharlieC]

Was there anything else plugged in to the Godlyke supply at the same time? Or was the one effect unit the only thing on that supply? Were there any extra daisy chain plugs uncovered, exposed, that could have been touching a metal surface?

The reason I ask all this is because using the Powerall by itself is exactly like using a Boss wall wart or a Zoom wall wart by itself, as far as ground loops are concerned. The Powerall does not have a special vulnerability to ground loops that the others do not have.

Now, there are other reasons why you might have gotten a hum. It could have been a bad connection with one of the Powerall's wires or jacks. The supply itself might have been faulty, e.g. with a poor ground connection internally. Or there might have been something external like an exposed plug touching a metal pedal or pedalboard.

Power-All to B3 direct, no daisy chain or other stomp boxes.

All quality cables and connections.

A quick swap to any other my other 2 power supplies cured the ground loop instantly.

My suspicion is that my other 2 power supplies are transformer-based and not switching supply like the Power-All.

 

[CharlieC]

... The supply itself might have been faulty, e.g. with a poor ground connection internally.

Perhaps, but the existence of the "ground loop disclaimer" in the operating manual is quite unusual for a wall-wart.

I may end-up contacting Godlyke to take advantage of their lifetime replacement guarantee and see where this goes.

 

[boomertech]

There is a problem with counterfeit UL safety with this product:

[Invalid or Expired Link Removed]

-Frank

 

[CharlieC]

There is a problem with counterfeit UL safety with this product:

[Invalid or Expired Link Removed]

-Frank

Thanks, Frank!

Mine is the second model listed, SK02G-0900200U

 

[boomertech]

Thanks, Frank!

Mine is the second model listed, SK02G-0900200U

Like Bongo was saying, the 9V output of the power supply should be ground isolated from the AC mains. Which would eliminate ground loop issues. The only way for a true ground loop to exist, is if the mains 'earth' blade on the plug is somehow (resistive or capacitive) electrically connected/coupled to the 9V negative output. If that's the case, then personal safety is questionable.

-Frank

 

[Dominic D]

I know this isn't the most useful info, but I've been using a Godlyke with a Zoom B3 and later a MS-60B for about a year with no issues. In fact, I've had the opposite issue where an older transformer PS makes a certain pedal noisy and the Godlyke fixes it.

 

[Downunderwonder]

The oldfangled transformer that supplys 18v to my Dunlop brick is pretty good. My Godlyke can't hold a candle to it for quiet.

A couple of my pedals are fussy little bitches and won't work quietly with anything but battery. RedDragon and BDPG.

 

[CharlieC]

Like Bongo was saying, the 9V output of the power supply should be ground isolated from the AC mains. Which would eliminate ground loop issues. The only way for a true ground loop to exist, is if the mains 'earth' blade on the plug is somehow (resistive or capacitive) electrically connected/coupled to the 9V negative output. If that's the case, then personal safety is questionable.

-Frank

I know this isn't the most useful info, but I've been using a Godlyke with a Zoom B3 and later a MS-60B for about a year with no issues. In fact, I've had the opposite issue where an older transformer PS makes a certain pedal noisy and the Godlyke fixes it.

Thanks for the input!

What I then still am curious about is why the user manual specifically recommends different AC circuits for the amplifier and power supply and warns of ground loop issues if their product were a ground-isolated design.

 

[Ewo]

Thanks for the input!

What I then still am curious about is why the user manual specifically recommends different AC circuits for the amplifier and power supply and warns of ground loop issues if their product were a ground-isolated design.

Me, too. IANA tech, but I always thought ground loops were _more_ likely when devices in the signal chain _weren't_ connected to the same outlet.

 

[Azure Skies]

I have noticed that digital units are much more susceptible to power supply noise, often from non-isolated power supplies. Using a power-all effectively makes mini ground loops within each of your pedals. Usually this is of no consequence due to the low current draw of the devices, or the relatively low level of the signal. However, the digital unit may not like this. It seems your experiment of using other isolated supplies for the zoom would support this.

 

[CharlieC]

Both the Zoom B3 and MS-60B can operate without instrument input connected.

I have since tried a few more experiments with just a single pedal under Power-All and connected to various amplification devices, using the same AC outlet. All tests resulted in ground loop hum. Simple swap to other known ground-isolated supplies resolved the issue.

I ran a third-party DI box between an individual pedal's 1/4" out and a powered mixer via XLR. No ground loop hum. No change even when toggling between GND and LIFT on the DI box. Direct connection from pedal to powered mixer via 1/4" (without DI box) resulted in ground loop hum using Power-All.

I connected the Power-All to a known-different AC circuit, leaving the amplification on its own AC circuit. Result was still ground loop hum by just way of 1/4" connection between the devices.

With this said, I believe ground loop hum is inevitable with my digital pedals under Power-All when directly connected to another AC powered device.

At this point, I do not believe the Power-All is defective, but instead, is incompatible with my particular equipment, and it is unfortunate that I did not discover this within the retailer's return period.

Cheers!

 

[squirefan]

Could it be polarity?

 

[CharlieC]

Could it be polarity?

I don't think so.

My DC pedal would not power on at all with reversed incoming polarity.

To no avail, I did however try flipping the Power-All orientation in the AC outlet.

 

[CharlieC]

I would like to mention that this ground loop issue with the Power-All and my equipment went undetected until my signal was recently scrutinized.

IMHO, not many would notice it, myself included, in a live band context, rehearsal room, or even at moderate home levels. Typical bass cabinets also assist in masking it.

Under studio, recording, or lab conditions, however, all bets are off!

 

[2.6kHz]

It could be a matter of ground polarity. Amp is positive ground, pedal is negative ground, or vice versa. Godlyke makes the ground hog which is an isolator that would fix the problem. Problem is the ground hog costs $30. Just looks like it is a transformer inline with a cable.

 

[HolmeBass]

The instructions from Godlyke do not say different circuits, they say different power strips, which is a much lower hurdle to clear.

 

[CharlieC]

It could be a matter of ground polarity. Amp is positive ground, pedal is negative ground, or vice versa. Godlyke makes the ground hog which is an isolator that would fix the problem. Problem is the ground hog costs $30. Just looks like it is a transformer inline with a cable.

The instructions from Godlyke do not say different circuits, they say different power strips, which is a much lower hurdle to clear.

Thanks, guys.

I think I will be sticking with an old school $10 wall-wart that neither causes me ground loop hum, requires polarity correction, additional purchases, nor me bringing even more stuff to the gig.