Naim and Their Ground Theory

Posted by: king on 30 May 2002

Hi Everyone,

I tried searching this forum on this but couldn't really find a complete answer to this:

I'm trying to appreciate Naim's way of organising the ground of various equipment.

From CDP to Pre-Apm to Hi-Cap to Power Amp to Wall outlet.

It starts from CDP, with one ground connect to the -ve signal (if you call it), plus the ground of the chasis.

The same singal line goes on to Pre-Amp which grounds the Pre-Amp chasis together with the -ve signal.

Then goes on to the Hi-Cap which connects also the 0vde of the regulator, ground the chasis, and also the -ve signal.
I'm assuming the ground of the 3pin plug of the Hi-Cap power cord is not connect to anything.

Finally this line goes to Power-Amp carrying the -ve signal and ground the chasis, and also acts as the 0vdc for the regulators.

And this finally goes to the ground of the wall outlet via the power cord.

Am I having the right understanding?

If so, isn't it too stress on this singal line which ground all chasis, acts as 0vdc for regulators and carries -ve signal?

Thanks in advance for your help.

Cheers.

King
Posted on: 31 May 2002 by Paul Ranson
Obviously the signal grounds must be connected together right through the system (we'll ignore 'balanced' connections for now). Very little current flows in the 0v signal, a couple of volts into 50 000Ohm type levels. This 0v is connected to 'real' earth in Naim systems at either the CD or turntable, but preferably not both.

Every box will have its case connected to the earth that comes in from the mains supply, this is a separate safety issue.

Paul
Posted on: 31 May 2002 by king
quote:
Originally posted by MartinC:
The CDP (or TT) has it's 0v connected to mains ground, and its case also connected to 0v.

The Preamp has the case connected to 0v

The Preamp PSU has the case connected to ground but not to the 0v

The Poweramp also has the case connected to ground, but not the 0v.
Martin


Martin,

This is more than what I thought.

Are you saying that the 0v of the CDP and the 0v in the Pre-amp are not connected unless they are plug into the same wall outlet?

As for the signal ground, it should start from CDP to Hi-Cap to Pre-amp to Power-Amp and finally to the earth wall-outlet.

I am assuming that all 0v (CDP and Pre-Amp and Hi-Cap), chasis (CDP, Pre-amp, Hi-Cap, Power-amp), and signal ground eventually meets at the earth wall outlet.

Am I correct?

Thanks

King
Posted on: 31 May 2002 by king
quote:
Originally posted by Paul Ranson:
Obviously the signal grounds must be connected together right through the system (we'll ignore 'balanced' connections for now). Very little current flows in the 0v signal, a couple of volts into 50 000Ohm type levels. This 0v is connected to 'real' earth in Naim systems at either the CD or turntable, but preferably not both.

Every box will have its case connected to the earth that comes in from the mains supply, this is a separate safety issue.

Paul


Paul,

Does the 0v and signal ground reach the earth of the wall outlet eventually?
If so, it doesn't matter how they are connected as liong as no loop is formed, right?

I need a big white board to figure this out..........

King
Posted on: 01 June 2002 by Paul Ranson
quote:
Does the 0v and signal ground reach the earth of the wall outlet eventually?

0v is signal ground. In a conventional Naim arrangement it is connected to wall outlet earth at the CDP or the turntable. It would work without this connection.

Paul
Posted on: 01 June 2002 by Andrew L. Weekes
King,

The best way is to examine the current paths, in order to understand it better.

Bear in mind current flows in loops, so whilst current flows from *cap to preamp and back via the SNAIC, there's no significant current flow from PSU to power amp back to PSU 0V, for example.

quote:
Very little current flows in the 0v signal, a couple of volts into 50 000Ohm type levels.


Actually, ALL of the current drawn by the preamp flows in the signal 0V connection (from PSU +ve, to PSU 0V, via SNAIC5), it's several hundred milliamps, primarily constant, but not totally.

quote:
This 0v is connected to 'real' earth in Naim systems at either the CD or turntable, but preferably not both.It would work without this connection.


But it wouldn't work as well as with it, as I've demonstrated clearly several times.

Andy

[This message was edited by Andrew L. Weekes on SATURDAY 01 June 2002 at 23:34.]
Posted on: 01 June 2002 by JeremyB
The star earth center appears to be on the PCB inside the pre-amp - the ground post is but one "point" of the star and not the center. Perhaps this is why grounding via both the CDP and the TT produces hum (like a loop antenna hanging off the pre-amp).
Posted on: 02 June 2002 by king
Thanks for all your response.

I will try tracing the connections inside to appreciate it.

Cheers.

King
Posted on: 04 June 2002 by king
Interesting discovery, at least for me.

I connected a non-Naim CDP, 62/140 last night in the normal Naim fashion and tested the connections.
What I found was that as the CDP power cord is a 2 pin affair (Japanese made)- this causes almost the whole ground connection - 0v and signal ground to be floated.
The only thing that is connect to earth is the chasis of the 140.

When I replace the CDP with my s/h CD3, the 0v, signal ground, chasis of CD3 and 62 are connected to earth via the power cord of the CD3.

Is this one of the many reasons why Naim CDP sounds better? I mean to have the 0v and signal ground earthed sounds more logical then floating them.
Posted on: 05 June 2002 by Andrew L. Weekes
King,

If you connect the TT earth tag of the 62 to mains earth you can then try the non-naim player with the same result.

I think you'll find it sounds better with the earth connection, but there's a whole lot more important reasons why a Naim CDP sounds better.

A.