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Testing grounding in a multi-format system
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Testing grounding in a multi-format system
Corbeau
I've held in this question for awhile despite trying to research as much as I can into the subject, but it still haunts me, so here goes:

I have a multi-format setup at the moment, namely, euro and banana systems: two separate 6U racks of Euro, one of which is my main sequencing and modulation rack, and is basically always mingling with a 2-frame Bugbrand system, a Serge Animal, along with numerous other little synths, drum machines, and standalone sequencers.

I've never really been able to know for sure if I have everything grounded properly. I'm not sure how to go about testing this, beyond plugging things in in a way that seems to ensure that there is common grounding between all the machines, and listening to and looking at the results to see if there is a problem. But I'm not 100% certain, when something doesn't seem to be working right, if it's due to simple user-error on my part (ie, dumb patching mistakes) or if there is a grounding issue, or a feedback loop or something like that happening.

Normally, I take a long banana patch cable and plug it directly into the grounding socket on the Bugbrand PSU. I'll then plug that into a format jumbler, and/or stack it with a banana-euro cable to connect to some input in the euro system, as well as the grounding socket on my Serge PSU (which was a custom made thing that another wiggler sold to me a long time ago). I also plug all of the wallwarts and power plugs into the same power-strip (although it seems to have two "channels," each with a separate power switch).

So, is there a sure-fire way to know that the grounding is good, so I can feel confident in troubleshooting?

I have a little digital oscilloscope and a digital multimeter. Would either of these tools help me test the grounding between all the machines in play?

Apologies in advance if I'm asking a really played-out question. I've just never quite wrapped my head around this issue and would appreciate some pointers. Thanks for any help.
Graham Hinton
Corbeau wrote:
I have a multi-format setup at the moment, namely, euro and banana systems: two separate 6U racks of Euro, one of which is my main sequencing and modulation rack, and is basically always mingling with a 2-frame Bugbrand system, a Serge Animal, along with numerous other little synths, drum machines, and standalone sequencers.

I've never really been able to know for sure if I have everything grounded properly.


Extremely unlikely, everything is stacked against you.

Quote:

I'm not sure how to go about testing this, beyond plugging things in in a way that seems to ensure that there is common grounding between all the machines, and listening to and looking at the results to see if there is a problem. But I'm not 100% certain, when something doesn't seem to be working right, if it's due to simple user-error on my part (ie, dumb patching mistakes) or if there is a grounding issue, or a feedback loop or something like that happening.

Normally, I take a long banana patch cable and plug it directly into the grounding socket on the Bugbrand PSU. I'll then plug that into a format jumbler, and/or stack it with a banana-euro cable to connect to some input in the euro system, as well as the grounding socket on my Serge PSU (which was a custom made thing that another wiggler sold to me a long time ago). I also plug all of the wallwarts and power plugs into the same power-strip (although it seems to have two "channels," each with a separate power switch).


Most wall wart type PSUs do not pass the mains Earth through so anything powered by them will not be grounded. Even PSUs with three mains pins often use the earth just for their protective cover (Frame Ground) and do not connect it to the outputs.

Banana system PSUs often have a banana socket for connecting to other PSUs, but this is not a good method and banana patch leads are not a good connection method because the resistance is too high.

Quote:

So, is there a sure-fire way to know that the grounding is good, so I can feel confident in troubleshooting?


If you feel tingles or hear a modulation when patching between systems (mains hum on CVs) then it needs to be improved.

There are two distinct issues:
1) Safety Earthing of each system separately and the overall system as a whole.
2) Establishing a common signal 0V.
Both have to work together. I have dealt with these on many threads, try a search.

Safety as a whole is different from individual system safety because when connected together individual PSUs may be disconnected from the mains and it still has to be safe. You can touch the patch cables so everything has to be referred to mains Earth rather than left floating. Do not rely on screened patch cables to provide a voltage reference via their screen, they may get pulled out and the resistance is too high.

Quote:

I have a little digital oscilloscope and a digital multimeter. Would either of these tools help me test the grounding between all the machines in play?


They will help. Most DMMs can't measure resistance below 1ohm and even top of the range ones with "four wire" measurements are not much use below 1milliohm and that is the sort of resistance in question. However even the cheapest DMMs are fine measuring voltage drops. The first thing to do is measure between the 0Vs of each system and find out how far they are apart. More than a couple of mV needs dealing with.

Here's the latest diagram showing how multiple PSU systems are connected together:



The thick blue lines represent distribution paths <1milliohm and you don't normally get that without busbars. The resistance of significant parts of wiring in the grounding is shown and the relative values are important. The thing to remember is that if no current flows in a wire then the voltage is the same each end and conversely if there is a current then the voltages differ. When you have amps flowing it becomes significant, that is why you shouldn't connect Earth to the PSU outputs. You can consider the banana jacks on PSUs as a TE (Technical Earth) terminal, just not a very good one.

First consider what happens with no connections between TEs (Rbond) or each system's 0V. The only wires joining separate 0Vs are via the mains leads so the path is about 300 milliohms. With screened patch cables another path of about the same value will be in parallel.

If you connect the TEs with substantial wire it is in effect putting another lower resistance in parallel. A better way is to join the 0Vs directly with an even lower resistance, either a bar for permanent installations or a Dinse connector for portable systems, that's what the 0V terminal is. They are normally used in welding equipment and very reasonably priced:



However you need 25mm2 cable between the plugs and at least 10mm2 cable (eg battery cables) internally to the 0V.

Here is how I connected one large studio together:



You are looking at the back of a large Wiard and Euro case and disappearing off to the vanishing point is a Buchla 200e system and a large Serge, there are also Bugbrand and other systems.
So instead of having wires between the TEs there is a long busbar measuring 0.56 milliohms running along the back and every TE is connected to that with bundles of 1mm2 cable (I would use 6mm2 or 10mm2 cable now). Systems without a TE terminal were modified to have one. Every system is less than 10milliohms from any other system and systems each end can be crosspatched with 10ft cables which was not possible before. There is no common 0V in this studio, but there are busbars inside the Euro and Serge cases.
Corbeau
Thanks so much for your reply, Graham, it is a super helpful quickstart guide on this, which appears to be quite a project in fact.

I'm going over all the links, documents and diagrams you offered. i have to say, I feel a bit in over my head (maybe this is electrical engineering 101 for most of you here, but I have 0 aptitude in math lol ) But it actually seems like a fun project so long as it doesn't completely drain my wallet hihi

But what I've been able to gather so far, is that I will need both a steel busbar, a central PSU for the entire system, and lots of adapter cable to plug everything in. That is probably a poor summation, but anyways I do have a couple of questions.

For things like the Arturia keystep, which of all my gear it gives me the most trouble with grounding it to my system, will it need to be connected to the bus bar too? Or am I overlooking a simpler solution.

And: when grounding one machine to another, does it matter you take grounding lead and plug it into an input? Would it work just the same with an output?

And finally, wallwarts, powerstrips...does your PSU system provide a way to get around these PITAs? That would be awesome.

Thanks again Graham, really appreciate the breakdown of things screaming goo yo

edit: sorry for any dumb typos, under the weather today...
Rex Coil 7
Corbeau wrote:
Thanks so much for your reply, Graham, it is a super helpful quickstart guide on this, which appears to be quite a project in fact.

I'm going over all the links, documents and diagrams you offered. i have to say, I feel a bit in over my head (maybe this is electrical engineering 101 for most of you here, but I have 0 aptitude in math lol ) But it actually seems like a fun project so long as it doesn't completely drain my wallet hihi

But what I've been able to gather so far, is that I will need both [an] ALUMINUM busbar, a central PSU for the entire system, and lots of adapter cable to plug everything in. That is probably a poor summation, but anyways I do have a couple of questions.

For things like the Arturia keystep, which of all my gear it gives me the most trouble with grounding it to my system, will it need to be connected to the bus bar too? Or am I overlooking a simpler solution.

And: when grounding one machine to another, does it matter you take grounding lead and plug it into an input? Would it work just the same with an output?

And finally, wallwarts, powerstrips...does your PSU system provide a way to get around these PITAs? That would be awesome.

Thanks again Graham, really appreciate the breakdown of things screaming goo yo

edit: sorry for any dumb typos, under the weather today...
See correction of your post above (in blue).
Graham Hinton
Corbeau wrote:
But what I've been able to gather so far, is that I will need both a steel busbar, a central PSU for the entire system, and lots of adapter cable to plug everything in.


Not steel, aluminium. Aluminium is a much better conductor, strong and lightweight.
Not a massive central PSU, multiple PSUs up to 2A. It makes the cabling simpler.
You can see some examples of large systems that I have built on my new Gallery

Quote:

For things like the Arturia keystep, which of all my gear it gives me the most trouble with grounding it to my system, will it need to be connected to the bus bar too? Or am I overlooking a simpler solution.


Objects like that are a PITA because they are poorly designed. They may work with a simple patch cable connection once everything else is has a common 0V established.

Quote:

And: when grounding one machine to another, does it matter you take grounding lead and plug it into an input? Would it work just the same with an output?


"Commoning" not grounding. As a means of last resort you could use the sleeve of an unused jack and it wouldn't matter if it was an input or an output.

Quote:

And finally, wallwarts, powerstrips...does your PSU system provide a way to get around these PITAs?


You will never find me making anything with a wallwart. They are beneath contempt.
Corbeau
Thanks for the helpful replies again, and for the all-important correction that the busbar needs to be aluminium, not steel - my bad d'oh!

This thread has been very helpful, I'm going to try to troubleshoot what I can with the info given here, but:

@Graham_Hinton, I'm definitely interested in exploring getting a better PSU system set-up, because I'm quite tired of dealing with the mess of power strips, cables, and wallwarts under my desk, plus the consistent grounding issues between all these formats. If you're not too busy to take on a new project, I'd like to see what we can do and what it would involve, it'd be much appreciated thumbs up
TheDegenerateElite
So what do you do with all the stuff made that uses wall warts?


Not use it?

Rewire it all?
Graham Hinton
TheDegenerateElite wrote:
So what do you do with all the stuff made that uses wall warts?

Not use it?

Rewire it all?


Sorry, I missed your questions.

Yes, don't use them if at all possible.
The only equipment I own that has wall warts is stand alone or isolated, e.g. network router, Flash programmer, KVM switch (looking around my desk), and I still hate them. I would never buy any audio equipment that has a wall wart for integration in my studio, that is my basic rule, and certainly no synthesizer where I would be touching the patch leads. A wall wart says a lot about a product and the company that makes it and it's not very complimentary.
moremagic
sometimes a wall wart just says "use me when you forget to buy a 9V"
MrsWedge
A well designed system should be able to run well using almost any kind of power supply, including used (thrift shop) wall warts.



10 wall warts forming 5 +/- 12v power supplies, over 10 amps on the positive rail. The supplies are not in any way connected together, and most certainly not earth grounded.

Wall wart are not even the slightest bit unsafe. If you short the output of one, It will either shut down until you remove the short and cycle power or will die quietly.
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