I need a lesson in ground connections

Hi friends. I needed a bus board quick so I grabbed a synthrotek. It has separate connections for the grounds. How should I hook these up to my Meanwell? With FCD72’s board there is just one ground connection. With this board I have 3. I guess i should check if these are connected, but if not, could i just run the ground from the Meanwell and then just jumper the grounds together?

Synthrotek Link

All GNDs should be connected.

Its just laziness to not connect them on the PCB i guess….

Do a continuity check between the 3 GND terminals. If they all ring out then only need to wire up one. It would seem like a weird design choice if all 3 are seperate.

I’ll do that tonight. Thanks guys.

Looking at the pic a little closer it looks like the GND pads are all on a ground plane so they should all be tied together. My guess is its set up like that if you piece different PS’s for the different voltages. Like a seperate 5v supply.

Thanks for taking a look. I was looking at some of the other photos as well, but couldn’t be sure. I check it with the meter.

The ground connections are tied together so it should be fine to just connect to one of them from the T60b.

Id suggest you use some thick wire… all the current from the 3 Rails will flow back this way.

Thanks for the tip Frank. Will do.

Another question. Over at Muff’s there is a discussion on the Meanwells that got me thinking. I have been using them for a long time now and never had any issues. However, a couple people are saying that the mains earth/ground should be connected to the common at the busboard. I have not done this. I just have the PSU common connection going to the busboard ground and the mains ground going to the Meanwell ground. Should I join the mains ground to the PSU common at the busboard? I guess that would just been one wire going back to the PSU mains ground connection. Thoughts?

After a nite of research things are even way more complicated than described below, please read the whole story!

Meanwhile this is the Summary:



I feel an Essay coming on……

Technically there is no GND on an AC Line, theres Line Conductor (LC)and a Neutral Conductor (NC), there is only an alternating Potential on the Line Conductor that swings around the Neutral Conductor.
Your PSU transforms this into DC Rails with various Voltages (+12, +5, -12V Potential in Respect of the “GND” in case of your Menwell) and a Rail with “GND” Potential, which is the Reference to your other DC Voltages but not necessarily exact the same Potential as the AC Neutral Conductor. Your +12V / GND / 12V that your Modules see could be as well +52V/+40V/ +28V seen from the Mains Perspective your Circuit will work just as well as long as its not connected to anything else that has a different Referecne to common AC Neutral Conductor.

Since you might want to do exactly this all PSUs try to generate the “GND” Rail as close as possible to the only common thing the can reference to, the Ground beneath your Feet. Please note that this physical piece of Earth is “Ground” not “GND”

So don’t ever connect your GND Rail to any of the Line or Neutral Conductors as there might or might not be a high Potential difference.

The third wire called “Protective Earth” is in fact connected to the “Ground” Earth (mostly with a Copper Line that is buried around your house) and it is used to protect you from failures in two ways: first, a metallic case is connected to the PE so if anything fails within the Current can flow away to the ground and second to avoid that the Neutral Conductors Potential is also tied to the Ground Outside so your Power LIne has a Potential of 230V AC that swings around the Potential of the Ground outside not some several thousand Volts more.

Your RCD (Residual Current Circuit Device) just measures that the Current in the Line Conductor and Neutral Conductor are exactly the same, since else Current flows somewhere else (as in the Example above thru your Body touching a wrongly connected Module from a wrongly connected BusBoard) and might kill someone, and in this case breaks the Circuit.

Now if you know this, you can understand that the “Ground” Problems come from PSUs that are not able to generate a “GND” Potential thats exactly equal to the Neutral Conductors Potential (or even worse, you have different Neutral Conductor Potentials), thus a current will flow and lead to Hum, Buzz, Noise and potentially death.

The solution is not to use “GND LIFT” switches that isolate the Unit from the Neutral Conductor and tie its GND Rails together, the correct Solution is to use a Symmetric Audio Line that isolates the different possible GND Potentials thru 1:1 Transformers. A “Servo” Symmetric Line that uses OpAmps will not help against Ground Loops, its just cancels away Noise from the Symmetric Signal Lines. BTW, these Transformers are the reason why real Pro equipment is way more expensive - it incorporates many many matched by hand transformers for the symmetric Ins and Outs instead of a just 5ct Op Amp. MIDI is another good example of this idea, the MIDI emitting device just drives an LED inside the Optocoupler, the GND of both devices is not connected via the MIDI Cable, the protective shielding is expected to be connected at just one side. The reason is that back in '84 when Dave Smith developed MIDI ICs were much more sensible to electrostatic discharge (and probably Mains Line Supply was even more worse than today in the US) so you would want to avoid any Potential Difference between 2 Circuits.

What we learn from this Excerpt is that the “Ground” Connector from the Mains Side of this PSU is meant to ground a Metallic Case (here the metallic case of the PSU itself) thru forcing it to the Protective Earths Ground Potential, so theres not deadly potential difference if you touch your device and something else thats grounded and its not meant to be used as Signal “GND” Potential Rail, although they are expected to be at the same Potential. Your Expectation may be wrong.

Again - and i know that i repeat myself - if you connect the Mains Side “Ground” and the Secondary Side “GND” two things might happen:

  • if the “GND” Potential is not exactly “Ground” a current will flow and you have a Ground Loop within your Device.
  • As the “Ground” is meant to carry Currents to the Earths Ground if anything fails it can have Mains Potential in Case of a Failure. This is not a Problem as long as Ground is just used to Ground anything but imagine what happens if your DC GND Potential becomes +250V within 20ms - at least you will blow some Rs, Cs and Chips (aka “pretty much anything”), at worst you are touching something thats tied to DC GND on your modular like an Aluminium Panel in just that moment when it becomes +250V and your Heart is in its vulnerable T Phase.

Conclusion: don’t tie GROUND and GND together. In most cases your PSU is able to deliver a GND thats exactly at the GROUNDs Potential but if anything fails you are deep into trouble.

More generally it might be a good advice not to blindly follow advices on Muffs as the average engineering expertise per thread theres seems to be at the same Potential as the average engineering expertise of a bag of Gummibärchen - at least if you reference it to the Tip of tying GND and GROUND together.


Is the PSU located inside your cabinet? If so there’s the possibility that mains power could get in contact with e.g. metal parts and you need to join your secondary ground with the ground from outside, all in one point (star configuration).
I guess when it’s outside and can’t get in touch due to the way it’s built it probably doesn’t matter much.

@fcd72 it’s called Schutzklasse 1. If you have mains inside it can get in touch anyway, no matter how little the probability may be. Some old machines (from before we were born) had an option to break the ground connection to cure hum loops if there was a shitty electrical installation in the studio. But that’s a huge safety risk and not advised.

Before you were born old man….

You are right about Schutzklasse 1 and usually Metal cases are painted to protect you for the time until the RCD breaks the circuit. But i detect a slight preference for shiny blank metal panels in Modulars……

What Rosch describes above only means secondary side DC GND being tied together NOT GND and AC Protective Conductor. Star GNDing might help. Or not.

Thanks for the lesson Frank. I read it and I’ll memorize it.

@fcd72 wrong. What I mean is you take the GND from the secondary side, for that matter all GND’s and connect them in only one point to the protection ground (PE, grün-gelb) that comes out of the wall. Only way to do it.

Yeah, don’t forget wearing your white Seppuku headband while you wire everything together :wink:

Haha, obviously you don’t need to do it, it’s only if you care about your life. Or if you care to stay out of jail in case you later sell the machine.

I think you guys just confused me more. I don’t plan on changing anything until I know for 100% what I am doing. I think it is setup as Frank and others before him described it here. I never had any issues. I just wanted more info on what was being discussed at Muff’s about the Meanwells.

@rosch My setup is multiple Ikea Rasts with the Meanwell PSUs inside. I use wood rails. I will eventually add an RT-65B to one of Frank’s laser cut cases and my performance case. These have aluminum rails if that matters.

Don’t get confused, rosch and i discuss some esoteric occurrence of GroundLoops that most likely never will happen to you.

All you need to know is the good old engineering rule to never connect secondary (in your case the DC +12/+5/GND/-12) Side of a PSU to the Primary (230V AC) Mains side and you are good to go.

If this results in hum, noise or other problems its more likely a problem of you in-house mains installation and all other tricks you may read about are just workarounds that might be dangerous. Id rather call an Electrician to check the Installation than use a Ground Lift Switch.

BTW especially in Electrics the only old rules are the ones that have been proved right, because false rules remove their originators automatically by electrocution :wink:

So don’t trust rosch, he licked at to many 9V Blocks as a child . . . .