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Do i need to ground/earth two units together?
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Do i need to ground/earth two units together?
helix
So i've just finished my DIY "monster" case.

One half of it is my old Doepfer DIY power supply, and the second half of it is a doepfer PSU2. I noticed the PSU2 has an earthing cable from the PSU to one of the bus boards, but the DIY unit does not. Never did.

Should i link the two together with earth? Will i get ground hum or noise or anything weird? I'm sure this has been asked but search isn't working for me still.

So far I've only got a doepfer bbd a-188 and it's pretty mad... lots of noise and feedback but i'd imagine i just haven't learnt to control it yet judging by the posts here! Love the sound one minute, then just turns to mush quickly... small sweet spots?!
wavejumperr
i've never had an issue patching two cases without a ground cable between them. i'm not a pro at this but from what i understand, having ground on the patch cables fixes the problem (as opposed to using bananas which don't have ground).
Rex Coil 7
... you may need to connect the zero volt rails of the two power supplies together (and NOT with a banana cable) ... but I'm sure as I can be that replies from more qualified people will show up soon ...

cool
cptnal
Before I built my own monster case (and congratulations on yours) I patched between three smaller cases with their own PSUs with no issues. My limited understanding is that hum comes from when two PSUs disagree about the value of "zero" volts, hence the joining them together to share that value.

(Patiently waits for Graham Hinton to rip me to pieces oops )
Rex Coil 7
cptnal wrote:
Before I built my own monster case (and congratulations on yours) I patched between three smaller cases with their own PSUs with no issues. My limited understanding is that hum comes from when two PSUs disagree about the value of "zero" volts, hence the joining them together to share that value.

(Patiently waits for Graham Hinton to rip me to pieces oops )
Nah ... I think you're pretty much right on the money there.

But just in case we're both full of it, I'll put out "The Call" .....

Foghorn
I put one of these on each case and connected it to the 0 volt buss.
Then 10 gauge wire between each case.
Since I used 10 gauge I felt it did not need to be in a star config.
I just daisy chained it.



If you do not do something like this, the ground between cases has to be established through the patch cables.
Some patch cables do not even have a ground conductor.
Some just have a single wire connected to the tip (hot) of the plug.

Foghorn
Rex Coil 7
Foghorn wrote:
I put one of these on each case and connected it to the 0 volt buss.
Then 10 gauge wire between each case.
Since I used 10 gauge I felt it did not need to be in a star config.
I just daisy chained it.



If you do not do something like this, the ground between cases has to be established through the patch cables.
Some patch cables do not even have a ground conductor.
Some just have a single wire connected to the tip (hot) of the plug.

Foghorn
Less than ideal ... daisy chaining and a single 10ga wire ... both less than ideal.

A good 1/4 pound of copper per foot would be far better. And putting the zero volt interconnect in more of a ~circle~ would be much better. Let's say there are three cabs and three PSUs ... Connect Cabs 1-2-3-1 together in a "circular" configuration:

1 connected to 2
2 connected to 3
3 connected back to 1

The idea is to create as little impedance as you can between all of the power supplies.

10ga wire = 0.032 pounds of copper per foot.

Far Better (minimum) = #4 cable at 0.124 pounds per foot. OR .. four parallel runs of #10 cable per each PSU zero volt interconnecting cable. And that's on the low end.

cool
JohnLRice
Rex Coil 7 wrote:
... you may need to connect the zero volt rails of the two power supplies together (and NOT with a banana cable)
razz Sure, there are better ways but I feel connecting all cabs together with 10 gauge wire and banana connectors in a star config is at least a little better than doing nothing at all and I doubt anyone would be able to convince me otherwise. hihi

All this stuff below seems to work well enough connected that way. If I even decide to move the studio to a larger room I might revisit how I'm doing things but until then . . . . .



The banana plugs I use are Mediabridge ULTRA Series
https://www.mediabridgeproducts.com/product/ultra-series-fast-lock-ban ana-plugs-2-pair-4-pack/
The cable I use from Acer Racing is reportedly very low resistance: 10AWG Superworm Silicone Wire with 1050 strands of 0.08 wire.
https://www.acerracing.com/ball_bearings/Superworm_Silicone_Wire_10_Ga uge_10_feet-1499-75.html
Rex Coil 7
JohnLRice wrote:
Rex Coil 7 wrote:
... you may need to connect the zero volt rails of the two power supplies together (and NOT with a banana cable)
razz Sure, there are better ways but I feel connecting all cabs together with 10 gauge wire and banana connectors in a star config is at least a little better than doing nothing at all and I doubt anyone would be able to convince me otherwise. hihi
100% Agreed. However note that I said several times it's "not ideal". I didn't say that 10ga wire would not work.

Let's remember that I'm the guy that puts gas tight paste on both side of lock washers used on the jacks of my modules. Why? Because, as you said, "is at least a little better than doing nothing at all". I take as many opportunities to optimize things as I can, even if it's only a small improvement. So I totally understand your position, and agree with it.

But if you're presented with an opportunity to do it just *that much* better, I say take that opportunity!

Physics and math tell us the optimal way to wire up our modular synths. It's up to us to either strictly adhere to those directions, or adopt partially correct approaches. But we cannot say that we "did it right" when we didn't take the path that physics and math clearly lay out for us. It's exactly like disobeying a stop sign. Rolling through the stop sign is not correct. You either stopped, or you didn't.

When someone asks what the best way to do something is, I'm not going to advise them to do it half assed. I'm going to tell them what I know about the right way to go about a given task. Now whether they go that route or not is totally up to them. I allow others to present the compromised approach.

seriously, i just don't get it
Mungo
helix wrote:
So i've just finished my DIY "monster" case.

One half of it is my old Doepfer DIY power supply, and the second half of it is a doepfer PSU2. I noticed the PSU2 has an earthing cable from the PSU to one of the bus boards, but the DIY unit does not. Never did.

Should i link the two together with earth? Will i get ground hum or noise or anything weird? I'm sure this has been asked but search isn't working for me still.
You'll find a lot of noise around this topic as already shown in this thread.

The Doepfer DIY supply is powered from an isolated transformer (does not pass the mains earth through) which is the simplest way to power equipment with unbalanced connections like eurorack modules.

When you connect multiple cases or equipment together with unbalanced cables they rely on the 0V (often labelled GND such as on the Doepfer bus boards) at both ends to be the same voltage. This is passed along the shield of the patch cable (ring connection of the 3.5mm plug).

When there are multiple paths connecting 0V you can end up with a ground loop, current flowing around the system causes the 0V points in different places to become further and further apart. You can often measure this with a multimeter, and it can change when you start plugging things together with cables.

The isolated transformer of your DIY supply has no connection to mains earth, which eliminates one of the pathways that creates ground loops. So its much less likely to cause any problems. Some people don't like the initial "thump" when you first plug in an isolated device, that is the 0V quickly becoming the same. So you can add a fixed cable between the 0V of the two.

If that works for you and has low enough noise, great, stop worrying and get on with making music.

Other people try and have everything connected through to mains earth, which needs more planning and adding lots of heavy wires around the place to keep the 0V close enough. And/or using balanced cables to join between different equipment. This works and can have better noise performance than unbalanced connections, but it can also be worse if not done correctly.

Some of those people spend a lot of money doing it and like audiophiles insist it is important and makes a difference even though they haven't checked if it did (which is not difficult with a multimeter or just making audio recordings of the noise floor). They might try and convince you to join their way of doing things, but you might be just wasting your money.
Mungo
wavejumperr wrote:
i've never had an issue patching two cases without a ground cable between them. i'm not a pro at this but from what i understand, having ground on the patch cables fixes the problem (as opposed to using bananas which don't have ground).
So simple! So true! The unbalanced patch cables make the 0V connection for you.
Rex Coil 7
I honestly don't care how anyone else configures their power systems. All I do is explain how I understand is the best way to go about things. Whether others mock the methods I've presented (as has been evident) or support the methods I've presented is of no concern to me. I'm not attempting to "convince" anyone of anything. I've nothing to gain by doing so. I also feel no need to provide test results regarding the effectiveness of the way I elect to configure my synths. I don't need to prove anything to anyone. I configure my power systems the way I see fit ... because I want to.

Some people have egos they need to coddle, so they feel the need to mock others because it's a proxy attack against various engineers within our membership that say things which deflate their fragile egos.

I've said all that needs to be said about this. I've offered practical and useful methods to configure their power systems. Beyond that, there's nothing else to say. This topic is not worth arguing over, life's far too short to bicker with those that insist my approaches are not to their liking. I will continue to go about building my synths as I see fit, and I will continue to provide my point of view to those that have questions. No matter what others have to say about that.

~Fin~

thumbs up
R.U.Nuts
Mungo wrote:
helix wrote:
So i've just finished my DIY "monster" case.

One half of it is my old Doepfer DIY power supply, and the second half of it is a doepfer PSU2. I noticed the PSU2 has an earthing cable from the PSU to one of the bus boards, but the DIY unit does not. Never did.

Should i link the two together with earth? Will i get ground hum or noise or anything weird? I'm sure this has been asked but search isn't working for me still.
You'll find a lot of noise around this topic as already shown in this thread.

The Doepfer DIY supply is powered from an isolated transformer (does not pass the mains earth through) which is the simplest way to power equipment with unbalanced connections like eurorack modules.

When you connect multiple cases or equipment together with unbalanced cables they rely on the 0V (often labelled GND such as on the Doepfer bus boards) at both ends to be the same voltage. This is passed along the shield of the patch cable (ring connection of the 3.5mm plug).

When there are multiple paths connecting 0V you can end up with a ground loop, current flowing around the system causes the 0V points in different places to become further and further apart. You can often measure this with a multimeter, and it can change when you start plugging things together with cables.

The isolated transformer of your DIY supply has no connection to mains earth, which eliminates one of the pathways that creates ground loops. So its much less likely to cause any problems. Some people don't like the initial "thump" when you first plug in an isolated device, that is the 0V quickly becoming the same. So you can add a fixed cable between the 0V of the two.

If that works for you and has low enough noise, great, stop worrying and get on with making music.

Other people try and have everything connected through to mains earth, which needs more planning and adding lots of heavy wires around the place to keep the 0V close enough. And/or using balanced cables to join between different equipment. This works and can have better noise performance than unbalanced connections, but it can also be worse if not done correctly.

Some of those people spend a lot of money doing it and like audiophiles insist it is important and makes a difference even though they haven't checked if it did (which is not difficult with a multimeter or just making audio recordings of the noise floor). They might try and convince you to join their way of doing things, but you might be just wasting your money.

Can we please close this thread and give it a sticky now. Because this post says it all and forever. I once asked a similar question which got pages of pages of replies and discussions. In the end I decided to ignore everything and to just hook up everything together with no further preparations and it worked with zero issues.
I think it was Mungo back then who finally posted something similar to this above which made me confident that I don't need no golden wires heavier and more expensive than my actual System. So thanks Mungo!
helix
Crieky, i thought this one could get heated!

Thanks guys for all your input and ideas. I'll see how it performs as is once i've got a few more modules into the new half and go from there.

I'd far rather get on with the music than worry about it, its taken long enough to build the thing in my small amount of spare time!


Thanks again smile
Rex Coil 7
R.U.Nuts wrote:
... I don't need no golden wires heavier and more expensive than my actual System. So thanks Mungo!
And yet more mockery, and all I am trying to do is help, and offer an alternative solution. I've learned my lesson, it won't happen again.

By the way, #4 cable is about $2.00 per foot. Hardly "more expensive than my actual System".

thumbs up
JohnLRice
Rex Coil 7 wrote:
JohnLRice wrote:
Rex Coil 7 wrote:
... you may need to connect the zero volt rails of the two power supplies together (and NOT with a banana cable)
razz Sure, there are better ways but I feel connecting all cabs together with 10 gauge wire and banana connectors in a star config is at least a little better than doing nothing at all hihi
100% Agreed. However note that I said several times it's "not ideal". I didn't say that 10ga wire would not work.
Just having a bit of friendly fun, not mocking what you do, just defending what I do . . . I think it's better than bad so . . . it's good! hihi
R.U.Nuts
Rex Coil 7 wrote:
R.U.Nuts wrote:
... I don't need no golden wires heavier and more expensive than my actual System. So thanks Mungo!
And yet more mockery, and all I am trying to do is help, and offer an alternative solution. I've learned my lesson, it won't happen again.

By the way, #4 cable is about $2.00 per foot. Hardly "more expensive than my actual System".

thumbs up


Sorry, I didn't want to mock you. But as I said, I asked about the same question a while ago which led to a discussion about what lenght and weight and material and whatnot a grounding cable should have. Basically all thes proposed cables were ridiculously fat, heavy and expensive and their use was totally not applicable for a gigging musician or a bedroom producer. The discussion was several pages long and left me with more question than answers whereas the simple answer could have been: "It's very likely that you won't run into any issues at all if you connect two PSUs without a special grounding cable. Just try and if you should have any issues report back."
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