Electrical Noise on rack

Hello

I'm having noise issues on an Erica Synths Case.
Case specs are 1.25A per rail (2.5A total), internal PSU specs are OUT ±12VDC / 1250mA, AC adapter power cord specs are 12V 3.34A 40W.
If I have the case turned off and with balanced 1/4 jacks from the Ciao line output into my line in audio interface I can hear the noise in the link below. Its like you can hear data voltage.
If I disconnect the power cable the noise is gone, so that makes me think the problem is not coming from any of the modules.
The noise is audible in the background when the modules are playing.
Any ideas on how can I sort this? Different power supply? DI Box with ground lift?

Eurorack Noise MP3

That's a ground loop. Your synth's P/S is trying to ground to a different ground than the equipment the synth is hooked up to, and this then allows AC to get onto the audio lines where the synth is finding an "easier" ground.

There's several possible fixes. The most immediate would be to use this: https://www.modulargrid.net/e/happy-nerding-isolator Transformer isolation with ground-lifts per channel and a useful ganged stereo level.

The BEST, however, is to implement a "star ground". Star grounds are called that because they're an array of wired ground lines that all connect to the same grounding point, usually on the mixing desk. What you'd need is a spool of 16ga stranded and insulated wire. Use that to connect ALL of the chassis, racks, instruments, etc etc in such a way that all of that winds up at your "star point"; in my studio, I have a number of 19" racks, and to connect those I'll simply hook a short bit of wire between each rack until I get to the point where I have to run the wire to the star ground. Time-consuming, but VERY effective. Implement that + the Isolator, and there should be ZERO noise problems after a tad of tweaking.

Hi Lugia, and Oldan,

Why not simply use the ground of your house's electric circuits? If that one has been done properly (since about the '60s or '70s that should have been done properly), I actually don't see an issue here. It wonders me actually that it happened at all... perhaps some issue with the electricity wiring within the house/apartment? It might be worth testing the ground within the building since this seems a pretty important matter to me... unless I am missing here something?

Kind regards and good luck with the troubleshooting, Garfield.

Actually, this results from house electrics already. When you have a typical unbalanced AC line, you get a "hot", "neutral" and "ground", and those go back to the main breaker panel. What the noise sounds like is that the modular is trying to ground itself to a different circuit, ground-wise. So what's going on is that the other AC circuit is flowing THROUGH the modular and getting into the audio, probably through it being connected to a mixer, etc that's on a different circuit than it is, which allows the AC into the audio.

This doesn't happen much in Europe, because European (and a lot of other) power systems provide BALANCED power. There's no "neutral", but instead you have two legs at 1/2 of the total mains voltage that are referenced to ground, which gives you the proper 230V for the device in question. But with OUR goofy power (and anywhere else there's unbalanced AC), that "neutral" and the associated ground line can provide a path for groundloops if you don't have either isolation to kill the loop or don't have a proper star ground. Sure, you can have balanced AC in the USA as well...but it's on YOU to put in the balancing toroids (imagine a 40 lb bundt cake...now imagine several of them, one per circuit). Very messy, expensive, and labor-intensive.

EDITED Jul 21st 2021, 01:39

Hi Lugia,

Hmm interesting and weird at the same time :-) I wasn't aware of that there seems to be a difference in the powering system (electricity I mean here) between let's simplify this to European (balanced?) system and the North American (unbalanced?) system. Is this applicable to Canada as well? I am asking since there is perhaps a very small chance that I might consider to move to Canada, but this unbalanced power thing might keep me away from doing so, sounds pretty bad to me and sorry to hear that you "suffer" from an unbalanced system. It seriously doesn't sound good to me, one must be able to rely on a good and properly grounded (electrical) system, in my humble opinion.

Though I have studied electricity circuits, I can't say I ever came across this balanced and unbalanced difference :-( Now that has been almost 30 years ago and professionally I haven't done much with that what I learned about that study, still I think I should call that educational institution and ask my money back ;-)

But here in Europe, at least those countries I know and I am aware of, we use here for most of the electricity "power connections" the 3-wire system. Same for most South-East Asian countries where I have lived too (afaik). One ground wire usually coded as yellow/green wire. Then you have a brown wire (we call it the phase wire; one of the three phases of which 3-phase AC electricity connection in the house from the "street connection" has been used from) that's as you called the hot wire, or simply the AC wire and we have a blue wire that's the zero or null wire, is that your neutral wire then? So to me it sounds pretty much the same as what you have in the USA? The ground wire is connected with a quite thick copper or nowadays even thicker aluminium (since that's cheaper than copper) metal bar that has been drilled or hammered down into the ground under or next to the house, to make sure you have a good "ground to the earth".

There is for small electrical devices, a two-wire system as well, then you only have a brown wire for the (AC) phase and a blue wire for the zero wire, there is no ground wire then. Most systems (critical but even less critical systems, for example, computers, audio devices, or whatsoever) usually use 3-wire plugs though and for those few small devices that don't have the ground then it is usually not too critical that it doesn't have the ground.

Now if I remember my electricity study well, it's highly forbidden (at least here in Europe from a safety and an electricity installation point of view) to have more than one ground, you must make sure when you do an electricity installation in a building that the ground is every where "the same" so to speak. Are you saying that you have more than one ground? Each electric circuit has it's "own" ground? If your answer to that is yes, then that seriously sucks ;-) If your answer to that is no, then I don't understand it at all ;-) Because then you have one ground as well and then it shouldn't be an issue.

If one connects all ground wires of all the electric circuits to that ground that leads into the earth (which is usually the case very nearby or even in the circuitry board/casing), i.e. the real "ground" or earth or whatever one likes to call it, then one shouldn't have any issues. But do I understand this correctly that you don't have a "real" ground in the USA (and perhaps in Canada)? Then how are you ever going to have a grounded system? To me that sounds like pretty dangerous too?

Interesting matter but extremely close to unbelievable as well, at least here from sitting in Europe point of view ;-)

By the way, you wrote this about the electrical system here in Europe: "There's no "neutral", but instead you have two legs at 1/2 of the total mains voltage that are referenced to ground, which gives you the proper 230V for the device in question."

That's however not correct, please refer to my above-explained 3-wire system we use here in Europe. We have the full 230 V on that phase wire as we call it (the brown wire) and then a zero or null wire (blue). Beside that, the ground wire (yellow/green). So there are no two wires that each provide half of the 230 V, that doesn't exist here, it wouldn't be AC then, it would than be rather DC.

Kind regards, Garfield.

Well, when I was running balanced power in the studio many years ago, the principle that we use here for that is to have a balancing transformer divide the "hot" leg into two legs of half-voltage with inverse phases. The equipment doesn't mind (in nearly all cases...but I know there's a few devices that don't like this) as a rule, and by doing that inversion, you wipe all of the noise that might be lurking on the AC thanks to phase cancellation. Also, the transformer helps to provide a more solid ground because there's no "neutral" for AC to sneak back onto in situations like this.

As for star grounds...they're not exactly THE mains ground line, which is what your codes refer to. Instead, this is more of a "noise ground"...it helps to kill stray induced garbage that's creeping around rackrails, gear chassis, etc. by creating a "universal ground plane" for the audio so that crud goes right to a single groundpoint that's designed to handle that garbage...this is usually a groundpoint on the mixer, which my Topaz 24 and FIVE both have. Years ago, I also had a Faraday shield under the floor of the studio that also connected to the mixer ground to catch e-smog creeping up from lower floors, and that was a very effective countermeasure at that time.

Hi Lugia,

Ha, ha, yes a Faraday shield under the floor is something that definitely might help :-) Keeps everything else off from that area :-)

Perhaps indeed a transformer that separates the power from the power supply is the best solution if you have unbalanced power, isn't it?

Well, I feel sorry for you and everyone else who lives in an area where only unbalanced power is available :-( I guess you might get used to it, but it gives you a bit more struggle to keep things nicely and especially easily grounded.

Do you know by any chance if the power is unbalanced in Canada too? Thank you and kind regards, Garfield.

Perhaps indeed a transformer that separates the power from the power supply is the best solution if you have unbalanced power, isn't it?

Yep...that's the only way TO obtain balanced power from unbalanced mains, in fact. As opposed to power supplies, there's no balanced power solution that doesn't involve a huge transformer of some sort.

Do you know by any chance if the power is unbalanced in Canada too?
-- GarfieldModular

It is...it's worth noting, in fact, that part of Canada's grid interconnects with the NE USA's in the east, and there's other interconnections further west along the border. When we had a severe geomagnetic event about 20-ish years back, the multistate power failure that resulted started in Quebec from the storm overloading their transmission lines with inductive currents.

The biggest culprit is plugging your modular synth into one outlet and having your recording system (computer and audio interface) plugged into a different outlet. If you can get both parts plugged into the same outlet that might be helpful for reducing or eliminating that ground hum. That would be the first thing I'd try to fix.

Next would be removing all the modules except for case power. Then add one module at a time or two or three. Power up the case and see if there's an issue with noise. You may have an inherently noisy module (digital modules with displays can do this). Or maybe a module that has failed in some way. It's good to rule out a bad module.

The biggest culprit is plugging your modular synth into one outlet and having your recording system (computer and audio interface) plugged into a different outlet. If you can get both parts plugged into the same outlet that might be helpful for reducing or eliminating that ground hum. That would be the first thing I'd try to fix.
-- Ronin1973

Spot-on, Ronin. I've found that the majority of audio issues revolve around that problem. The fix in a large studio is to star-ground EVERYTHING...including the AC outlet ground pins! And they'll use some voodoo wiring for that, some OFC or Mogami alloy nonsense...but really, all you'd need is some stranded 18ga hookup wire from Home Depot, etc and you don't necessarily have to go bonkers with wiring every...single...outlet. Just connect everything so the wires aim toward their destination at the groundpoint on the mixer, and that SHOULD fix at least 80-90% of the crud. It's also a good bit easier than diving into the modular's guts...but if you've gotta, you gotta!