Signal Ground Again!

thanks for your quick reply. It's this section in the manual that is confusing me, it relates to a connection termed ground signal;

What it's saying is that the earth wire in the mains plug must always be connected. The little screwy terminal on the back of the Supernait is only used if you have a turntable. As you don't have one, you don't need to use it. Simple as that. 

great stuff. I was getting worried when reading certain threads about ground loops etc. Thanks for putting my mind at rest

cheers

Douglass posted:

... My question is from a safety perspective, is this set up ok? Or am I supposed to connect the signal ground?

 

From a safety perspective, provided you are using a normal IEC mains lead to the Supernait with the earth pins connected, such as the mains lead supplied by Naim, then that's fine.

However, regarding this bit in the text you quoted: "In order to avoid hum loops, the signal negative of the whole system should be connected to the mains earth (ground) in one place". I don't think it's possible to say if you have mains earth connected to signal negative in one place, more than one, or none! Once you're outside of using Naim sources this area is a nightmare unfortunately. If you've inadvertently setup a ground loop by having more than one earth connection to signal negative, it may not be obviously audible as mains hum but it will subtly degrade performance of the system.

I'm using a Chord Qute EX DAC as my only source and to ensure an earth connection to signal negative I run an earth wire to the ground terminal on the back of my Supernait and ensure that the DAC and anything else connected to it is floating. The ground terminal on the back panel connects to signal negative inside the amp.

Sorry to confuse, but it simply isn't that simple an area that anyone can be sure of your earthing arrangements without careful examination of the devices you are actually using and what else is connected to them.

One thing - if using in an AV hook up you may end up with a ground loop, causing humming in speakers or a subwoofer.

Adam Zielinski posted:

One thing - if using in an AV hook up you may end up with a ground loop, causing humming in speakers or a subwoofer.

The simple solution to that is to use an optical IC (if that facility is available to you). 

Allan Probin posted:

Douglass posted:

... My question is from a safety perspective, is this set up ok? Or am I supposed to connect the signal ground?

 

From a safety perspective, provided you are using a normal IEC mains lead to the Supernait with the earth pins connected, such as the mains lead supplied by Naim, then that's fine.

However, regarding this bit in the text you quoted: "In order to avoid hum loops, the signal negative of the whole system should be connected to the mains earth (ground) in one place". I don't think it's possible to say if you have mains earth connected to signal negative in one place, more than one, or none! Once you're outside of using Naim sources this area is a nightmare unfortunately. If you've inadvertently setup a ground loop by having more than one earth connection to signal negative, it may not be obviously audible as mains hum but it will subtly degrade performance of the system.

I'm using a Chord Qute EX DAC as my only source and to ensure an earth connection to signal negative I run an earth wire to the ground terminal on the back of my Supernait and ensure that the DAC and anything else connected to it is floating. The ground terminal on the back panel connects to signal negative inside the amp.

Sorry to confuse, but it simply isn't that simple an area that anyone can be sure of your earthing arrangements without careful examination of the devices you are actually using and what else is connected to them.

 

 

 

Thanks for that. I am now confused though :-/ is it best just to assume that I have more than one earth connection? I have multiple appliances connected to an eight gang conditioner which connects to a wall socket. Only two of these connect to the amp though. 
What are you connecting to the ground loop? Where dies your earth wire connect to at the other end? Thanks

 

 

 

 

Hi Douglas

A small suggestion, without sounding too rude - please read on Wikipedia or other source what ground loops actually are.

Ground loops are unfortunately unaviodable in complex setups. One of the probles starts if some of the componens are earthed (like NAIM) and some not (like most of the Japaneese AV equipment). But.... Even if all were earthed properly, you would still probably end up with one anyhow ))

The only proper way to get rid of the audible hum in your speakers is to run an isolating transformer (commonly used in pro-audio setups). A decent one will set you back a wild sum of 10 pounds. Typically the isolating transformer can be placed in a signal path from source to a sub, or source to an av amp.

Good luck!

Adam

If you have a ground loop, and it is unavoidable, then you can use a ground loop breaker. There is no magic to ground loops, it simply is a conducting circle where dominant field strengths such as the mains electromagnetic field is coupled into the conducting loop, and a voltage is created.. This is why ground loops typically hum at mains frequency, but not always.

a good quality ground loop breaker can simply insert a resistance in the signal ground path. The audio signal has a very low current and so the voltage drop is minimal, however the resistance makes the conducting loop very lossy, so the induced voltage is minimal (although not entirely eliminated)

Simon

It is worth clarifying that there are two distinct areas here.

1) Mains earth, which is a connection from the component chassis (and key safety related parts of the internal PSU) to the earth pin on the power plug. This is a safety issue and must not be interfered with
2) The signal ground connection, which provides a reference point for all analogue connections in the system. This is where the signal negative is tied to mains earth. This should ideally be at only one point in the system and is usually provided by a Naim source component.
This is where things get interesting

a) if you have a ground loop, where more than one component has its signal ground connected to earth. This manifests itself as a distinct hum usually at mains frequency. As others have noted the only effective way to remove this with analogue connections is to identify the component and fit a ground loop isolator/breaker in between the component and the amplifier. If an optical connection can be used then even better.

b) Much more common in my experience especially with 3rd party source components is the lack of a signal ground to earth connection. This manifests itself as a distinctive buzz as opposed to a hum. This is much easier to cure and just needs somewhere in the system a connection between signal ground (e.g. the outer of an RCA connector) made to mains earth.

Back to the OP's question, if you have neither a buzz nor a hum from you system then don't worry....
Hopefully that helps, the above was gained from hard earned experience over many changes in my Naim system over the years

Douglass posted:

What are you connecting to the ground loop? Where dies your earth wire connect to at the other end? Thanks

 

 

I've obtained a green and yellow earth wire from an unused IEC mains cable (the rest of the cable discarded) and connected one end to the ground terminal on the back of the Supernait and the other end goes to the double mains socket that terminates my dedicated mains spur. The mains socket is attached to the wall using a surface mount box so it was quite easy to find a means of taking the earth wire inside the box and connecting it to an earth terminal on the back of the double socket. Other methods are available ... and as a disclaimer, please consult a professional electrician ... and electrical regulations, etc.

Also, take a look in the FAQ section of the forum for "A few reasons why we use DIN connections", the bit about maintaining a single path the earth. Although it discusses the multiple paths to earth that the use of RCA connectors introduce, this is absolutely relevant to when you have multiple sources, even if connected by DIN plugs

That is simply doubling up on the mains cable earth that terminates in/on the Supernait case.  - its doing nothing.  

Mike-B posted:

That is simply doubling up on the mains cable earth that terminates in/on the Supernait case.  - its doing nothing.  

 

No, the earth terminal is insulated from the case and connects internally to signal ground. Take a look on the back, you'll see an insulator for this reason.

None of what you described above will solve them.

thanks, it seems more complex than I thought but i'll do some reading up as suggested. Thankfully, at the moment I do not detect a hum or buzz which is good, although I assume if it's not set up right there could be underlying "noise".

Thanks for the responses

cheers

It's all fine, don't worry.