Groundloop.

[Claus-DK]

What is a groundloop ??
What causes it ??
How does one prevent it ??

If an amp is only plugged into the power and nothing else is connected to it (exept phones), is it even possible to make a groundloop ??

[Solderdude]

I plan to write an article on ground loops as it is a very complex thing with multiple possible ground loop paths.
Will take me quite some time to do so.

In short if an amp is only plugged in and only a HP is connected and nothing else you cannot have a ground loop.
Also a CD player into a portable amp (battery powered) into a headphone does not have a ground loop but for HF garbage does have one.
However, it is highly unlikely it will have any influence.

a ground loop exists as soon as 2 pieces of hardware both fed via their own mains supplies have different leakage currents.
These leakage currents will flow though the SHIELD from one device to the other one via the interlink and depending on how well the connected equipment is designed and how low Ohmic the shield of the interlink is some artefacts can be heard.
This can be in the audible range as hum, high-pitched hum, strange noises and could also be caused by high-frequency garbage that in itself cannot be heard but interacts (combination of signals) or is rectified (as an AM radio detector does) and become audible ABOVE a certain threshold.
The latter is well known if a GSM is close to a device and is being called.

Very complicated to determine how the loop is created and what can be done to break it or lower it below threshold levels of detection.

[Claus-DK]

Thanks, I look forward to read an indept article about those things, I think it is a bigger problem and causes more grief than we imagine, so getting more knowledge is a good thing..

This maybe be a bit supid to ask about, but if I plug in an amp and a CDplayer, put them on top of each other and switch them on, without connecting them with the RCAcable, can that create a groundloop ??
Or do we have to have two connections i.e a set of RCA and plug both things in to it to happen ??

If we connect via a RCA and plug into the outlet but leave the CDplayer at the off position would that be able to create the Loop ??

Will the amount of components in a device add to the rsik of getting a groundloop ? in other words is stuff filled with parts be more vunerable to it than a relative simple tube amp whith few parts ??

It is a bit like black magic to me when it comes to this comlicated electrical stuff, so forgive me for asking about things that seems to be crapped out of the air, but that is how my brain works and helps me understand things..

[Solderdude]

Thanks, I look forward to read an indept article about those things, I think it is a bigger problem and causes more grief than we imagine, so getting more knowledge is a good thing..

I can assure you it is a problem and much more relevant that most people think even technicians.., especially when computer audio or multiple equipment each with their own SMPS (Switch MOde Power Supplies) is used.

This maybe be a bit stupid to ask about, but if I plug in an amp and a CDplayer, put them on top of each other and switch them on, without connecting them with the RCAcable, can that create a groundloop ??
Or do we have to have two connections i.e a set of RCA and plug both things in to it to happen ??

No ground loop BUT the transformers IN the equipment still have a stray magnetic field unless they are screened with mu-metal which usually is not the case.
These magnetic fields can induce a hum in a device placed on top of the other one and depending on the sensitivity of the 'receiving' design could cause a low level hum.

To create a loop we have to have a physical loop.
The loop is as follows: mains -> CDP(power supply) -> interlink -> amplifier (power supply) -> mains.
The leakage currents in the power supplies CAUSE a difference in voltage (and cause a current when it can flow) as the power supplies have different leakage properties.
These different voltages with respect to the mains are connected via the interlink and thus want to equalize themselves.
They do this by creating a current determined by leakage of each power supply and this runs via the audio path (actually the screen)

If we connect via a RCA and plug into the outlet but leave the CDplayer at the off position would that be able to create the Loop ??

That would depend on the type of power supply used and how that is switched (via an interruption in mains or a remote control and software power supply button) so it will be hard to say unless you have one of those mains power monitors in which case you can see if it is really off or not.

Will the amount of components in a device add to the rsik of getting a groundloop ? in other words is stuff filled with parts be more vunerable to it than a relative simple tube amp whith few parts ??

Alas no it has no bearing whatsoever. It all depends on the physical build and wire routing as well as the used components and take countermeasures by the manufacturer.
It also depends on the used power supply, linear (transformer) or SMPS makes a lot of difference.
You should realise that most equipment nowadays is filled with SMPS.
Also from the pictures seen on the web of various equipment I can say with a high degree of certainty that MOST DIY efforts as well as most 'audiophile' equipment is very likely to be highly susceptible to these problems by the nature of their build (wiring, PCB layout e.t.c.)

It is a bit like black magic to me when it comes to this complicated electrical stuff, so forgive me for asking about things that seems to be crapped out of the air, but that is how my brain works and helps me understand things..

believe me even for experienced EE's the whole groundloop stuff is confusing and hard to pinpoint.
I run into it myself from time to time and it is even part of my daily job ...
It is quite complex matter.

[Solderdude]

Here is a tutorial I wrote on another website that is of relevance..



How to get the lowest amount of interference in your audio system.
This goes for all analog as well as digital and analog and is based on asymmetry in power supplies be them SMPS (switch mode) or linear (transformer)

Remove all interlinks so you have ONLY separate equipment.
Note that equipment that is double isolated differs from those that have safety ground.
Also note that safety ground is NOT a the same as RFI ground !
In general all safety grounds are extremely lousy RFI grounds.

You will need a voltage finder.
I use a sort-of screwdriver tester designed to show Live an Neutral.
Not the kind with a neonlight in it but this one can show voltages in a few coarse steps.
Another option is to use a multimeter.
It should have AC voltage AND AC current measurement capabilities.

Connect a mains fed audio component to mains (3 pin to 3 pin socket) and hold the tester against the RCA or other connector (the screen or common).
OR multimeter:
1 testlead to a safety ground or something you KNOW is REALLY grounded.
Other testlead of the meter to the RCA shield or other connector.
Set the meter to ACV(oltage) first and choose the highest range.
Set the meter lower when needed.
Note the voltage.
Now set the meter to AC A(mpere = current.
Same testleads on the same pins/conditions
Choose a setting of several 100mA (10A settings won’t show anything).
Go to lower settings to read a proper value.
Note that current.

Now, and this is NOT possible in certain countries, plug the mains connector in the mains outlet but phase reversed (rotated 180 degrees).
Redo the measurements and compare the results.

Mark the lowest voltage/current setting on the mains socket and mains plug so you can always find the lowest current.

Quick and dirty method only your finger and sometimes a metal surface needed.
Plug in the single audio component and make sure it is on something isolated (plastic or something)
Now rub your finger over a metal cover or put a metal plate on top of the audiocomponent and connect that to the shield of the RCA connector with some wire.
If you ‘feel’ your fingertip (where you touch the metal) to ‘bounce/vibrate’ a bit you will know there is current leakage.
When you feel nothing the leakage is very small.
Again reverse the polarity on the mains plug (rotate the plug 180 degrees) and test again.
Note the position of the plug opposite a mark on the mains socket for the lowest ‘ripple/hum/bounce/vibration’ in the finger tips.

Note that equipment with figure- 8 mains connections also need to be marked as these can easily be set in the wrong position.

When all equipment is tested and set for lowest leakage current connect them with clean interconnects (clean the RCA’s too if dirty/oxidised) and this will be the best situation.

Those with weird sounds or plagued with ticks from external equipment e.t.c. or faint hum or whizzing noises may find their equipment to be totally silent.
If still plagued with unwanted signals then one can resort to ferrites (do little if nothing mostly), mains filters (may also worsen things !) or separation transformers.

[Solderdude]

I have put up a basic tutorial about groundloops here:
http://diyaudioheaven.wordpress.com/tut ... -supplies/

scroll down to about halfway in the page.