Recommended reading on grounding?

Can anyone recommend me some reading on grounding and/or ground loops in a small studio setup? I’m currently running into an issue where I’m getting a lot of noise from the outputs of my Waldorf Micro Q Keyboard, but only when I also have the outputs of my MPC 1000 plugged into the mixer.

The Waldorf Micro Q Keyboard and the MPC 1000 are the only pieces of gear with a 3-pronged instead of a 2-pronged power plug in this setup. They are in fact ungrounded for the simple reason that I don’t have a power outlet with ground anywhere near my setup.

? wtf?
Ungrounded power outlets are imho an absolute no-go. Without a common ground, potential differences are very likely to happen. And very unlikely to solve !

Most gear these days comes with an external power brick and a two-prong plug so that’s by definition ungrounded. Isn’t not connecting the ground supposed to solve hum issues? (Even though it’s not recommended, because it’s unsafe on devices with a metal case and integrated power supply.)

Time to redo the wiring in my house, apparently.

Best is to have ground coming only from one central point. As soon as you use more points for grounding you are creating loops of wire that can start to function as an antenna.
IIt also safer to have ground at least somewhere in the chain…

No, they bridge the so-called ground internally against one phase. And this is what makes the issue to a game of luck. My experience with wall warts (or such externally two-pronged power supplies) is, that you have a fifty-fifty chance that you will have no ground loop hum. The funny thing in my studio is that wall wart number 1 of synth number one will work in one power distribution and will provide a mean hum on a different power distribution on the same power circuit with common ground. With Pro stuff (with C13 3-pronged power plugs): no issue wherever i plug them in.
And i use balanced cables or bridged patch cables in my audio path, so it is very unlikely to catch dirt here…

Rane have some good reading on audio grounding… and other stuff
grounding and shielding

Thanks, @funkyfli. I also found the SoS Ground Loops Explained article.

Incidentally, I should assume the main outputs of most synths are unbalanced unless explecitly stated otherwise in the manual, right?

Yes hardly any synth has balanced outputs… And in a normal studio situation it’s also not really necessary. Balanced signals are mostly intended for low level microphone signals and carrying signals over long distances.
But of course it always has some benefit and all pro studio equipment uses it.

I object, your honour !
Synths are not intended for long distance cabling, but AD/DA are and their inputs and outputs are balanced through the complete zoo, regardless if it is ADAT, AES/EBU or MADI. Because these are intended to bridge further gaps than 3 - 5 meter. My experience so far is, that any audio cabling longer than 3 meter is possibly critical for external influences, as you cannot exclude the fact, that sometimes you are forced to cable audio and power in parallel. Life is no pony farm…

What part do you object to? I was assuming use of short cables in a normal (production) studio situation.
If was astonished by reading the rane article link with lots of problems I never encounter in practice while working as a sound engineer in live situations.
In my experience all the pro gear always works flawlessly together with standard balanced ground shielded cables. Problems with hum always being the cause of broken cables or gear or a laptop power supply. (or none audio equipment doing horrible things to the mains)

Oh and when using unbalanced cable you of course have to be a bit sensible not to run them past or over strong electromagnetic fields. (again mostly laptop power supplies these days)

I found the rand article very interesting. I immediately believe you rarely run into practical issues these days, but it does explain what’s going on and how mixing balanced/unbalanced and confusing chassis vs. signal ground can get you in trouble.

To summarize; it’s not an issue until it is an issue, but when it is an issue it’s nice to understand what’s going on and how to fix it.

Ok these issues are ratsnest.

@t2k run an extension cord from a part of your house that has proper earth connection to your studio to test if it helps before you start rebuilding your house.

There, I fixed it!

@shiftr I was indeed planning to try that as well, but I’ll have to buy a longer extension cord first. I’m pretty sure having proper mains grounding will solve this issue as well, but the above “solution” should do for now.

obviously you are a bit tired of life….

@fcd72 They weren’t connected to a grounded outlet anyway, so this doesn’t add any additional risk.

I guess the real question is; how (un)safe is it to connect a fairly modern (post-2000) device with a 3-pronged power inlet to an ungrounded power socket in a home environment?

As long as everything is in working order its no risk at all. The Schutzleiter is especially for occasions where not everything is in working order……. so if you find out its to late. But as a friend of mine said - “Its only 230Volts!”

On the other hand: if you outlet isn’t connected to Ground - you indeed could have solved the Problem as may have interrupted the GND Loop this way….

> The Schutzleiter is especially for occasions where not everything is in working order…

Sure, but the question is whether or not we can reasonably assume that internally, the power supply is properly isolated from the case, just as with devices that come with a 2-prong power plug such as my vacuum cleaner, fan, printer, etc.