NDS Signal Ground Switch

Mike-B posted:

Intrigued by all this I've just had a fiddle playing iRadio on NDX & BBC R-3 on NAT-05.   I reset my NDX to Floating & found it did not make much of a change that was that obvious,  maybe a touch less focus in soundstage & something a bit vague in the general SQ.  

More fiddling between Chassis & Floating signal ground switch, this time with UPnP & I took my time & listened to Floating for 2 albums to get used to it.  The difference between Chassis (correct for me) & Floating is more obvious with this time,  maybe it's with UPnP;  with Floating I get the same vague focus in sound stage & voice/instrument positioning,  bass although still there but does not have as much impact/slam,  midrange & treble are not as detailed & dynamics seem softer.  However (& I guess because I don't have multiple grounds)  there is no hint of multiple ground hum or strange noises from the speakers when idle or playing.    Then I went back to Chassis & thats when I really hear the difference,  it all snapped back,  sound stage was wider & more focused with voice/instruments fixed in space & moving (as recorded) forward or back in the mix,  bass has its grunt back,  mid & treble detail is all there.   All rather satisfying to confirm its all as it should be,  but enough of the fiddling,  it's listening & relaxing time. 

Alba1320 posted:

AFAIK, If the CD player was being used as a CD player, with its analogue output connected to the amp (DIN-DIN), yes; in this instance, however, the CD player is being used as a 'transport', with a S/PDIF connection to the NDS, which means the NDS is the only source connected to the amp (DIN-DIN), so it should be set to chassis to provide the signal ground reference for the system.

Thanks Alba, usually when I see post like this I don't participate, over my head.

After glancing over the replies, I see this discussion is for multiple sources.

 Single source Cdx2 Mk I, and 282, no switches.

I guess, just basic equipment ground, by way of mains. 

But wow, the way you explained it, simple, one doesn't haft to be an engineer to understand it.

And the Icing on the Cake, Simon, and Richard consigned!

Always information to be had on the sidelines.

No rancorous replies on an informative post, I love it!

Allante93!

Alba1320 posted:

AFAIK, If the CD player was being used as a CD player, with its analogue output connected to the amp (DIN-DIN), yes; in this instance, however, the CD player is being used as a 'transport', with a S/PDIF connection to the NDS, which means the NDS is the only source connected to the amp (DIN-DIN), so it should be set to chassis to provide the signal ground reference for the system.

I believe that to be wrong (but will stand tobe corrected),  S/PIF carries the grounded signal from the CD player to the ND & that needs to be the only signal ground;  having the ND set to Chassis gives two signal ground points (albeit in series).    It would be correct to set the ND to Chassis if the CDP to ND link was optical.

The ND manuals are far from clear on this point,  but my logic is taken from the nDAC were it does say the nDAC needs to be set to Floating to carry the CDP's signal ground to the pre-amp. 

"Select the Chassis position unless the DAC is connected in a hi-fi system incorporating another earthed source component, or mains hum is audible through the loudspeakers. 
Note: All Naim CD and DVD players are earthed so the Signal Ground switch should be set to floating if one is connected in the system"

Mike-B posted:

Alba1320 posted:

AFAIK, If the CD player was being used as a CD player, with its analogue output connected to the amp (DIN-DIN), yes; in this instance, however, the CD player is being used as a 'transport', with a S/PDIF connection to the NDS, which means the NDS is the only source connected to the amp (DIN-DIN), so it should be set to chassis to provide the signal ground reference for the system.

I believe that to be wrong (but will stand tobe corrected),  S/PIF carries the grounded signal from the CD player to the ND & that needs to be the only signal ground;  having the ND set to Chassis gives two signal ground points (albeit in series).    It would be correct to set the ND to Chassis if the CDP to ND link was optical.

The ND manuals are far from clear on this point,  but my logic is taken from the nDAC were it does say the nDAC needs to be set to Floating to carry the CDP's signal ground to the pre-amp. 

"Select the Chassis position unless the DAC is connected in a hi-fi system incorporating another earthed source component, or mains hum is audible through the loudspeakers. 
Note: All Naim CD and DVD players are earthed so the Signal Ground switch should be set to floating if one is connected in the system"

The CDX2.2 manual says something along the lines that the S/PIF output is galvanically isolated. In my mind that would also mean that the common earth is disconnected.

I think we need some clarity form Richard Dane on this one.

Mike, the BNC Coax S/Pdif input of the ND5 XS is galvenically isolated (I tested it!).

Adam Zielinski posted:

The CDX2.2 manual says something along the lines that the S/PIF output is galvanically isolated. In my mind that would also mean that the common earth is disconnected.

I think we need some clarity form Richard Dane on this one.

Agreed,  or maybe better for Naim to rewrite the manuals.  Maybe update the old "Connections" manual.    But I just looked in the current CDP manual & can't find anything on S/PIF being galvanically isolated.  

Huge posted:

Mike, the BNC Coax S/Pdif input of the ND5 XS is galvenically isolated (I tested it!).

OK, but what & were is the isolation point & does it also isolate the signal ground path from the CDP ???

The NDX white paper does not make this point clear other than say there are galvanic isolators within the NDX.   It really needs some clarification (& a manual re-write)  from Naim

Isolation
To reduce noise transfer to the analogue domain from its digital circuits and connections the NDX incorporates  galvanic isolation between key sections of its circuit. The digital audio data source is isolated from the DSP and, in turn, the DSP is isolated from the master clock and DAC. In this way the maximum isolation is achieved between  digital sources and analogue output. Power supplies for each section of the signal path are also independent, as explained later.

Adam Zielinski posted:

The CDX2.2 manual says something along the lines that the S/PIF output is galvanically isolated. In my mind that would also mean that the common earth is disconnected.

 

Correct - that is exactly what galvanic isolation means in this scenario. I believe Naim galvanically isolate all their SPDIF outputs - which is why Naim works so well with Hugo for example which uses no galvanic isolation. There is a line of engineering thought that says you should only have one set of galvanic isolation - two galvanic isolators across a common connection will start to reduce signal integrity - especially if the isolation is achieved through magnetic coupling

S

All this is most likely correct but Naim really do need to step up & clarify the ground switch protocol for all the variables.    To me the analogue connection is clear,  the problem arises in the digital out/in puts;  if they are galvanically isolated & the CDP signal ground is not carried through,  fine,  but the nDAC manual hints at either that not being so or the manual is wrong.     

"Select the Chassis position unless the DAC is connected in a hi-fi system incorporating another earthed source component, or mains hum is audible through the loudspeakers. 
Note: All Naim CD and DVD players are earthed so the Signal Ground switch should be set to floating if one is connected in the system"

Mike when I measured using my multimeter and confirmed on my NDX - the ground switch refers to the ground of the signal - and it either 'floats' or is grounded to mains earth potential and not the SPDIF ground. What I can't remember when I measured - is which side of the signal ground relays the grounding is applied to . I suspect its the external side of the relays - but I can check later

The SPDIF output has no bearing on this  - no doubt because of its galvanic isolation.

Thinking it through once could get some awful earth loops if one did not use galvanic isolation on the SPDIF and you hear about this from time to time on other forums with non Naim equipment - i.e. mains hum induced when the SPDIF lead is connected.

Simon

So what that actually means is with a set up like:

- NDX and CDX2.2 connected digitally to nDAC (via DC1).
- nDAC then connected via DIN analogue to a pre-amp.

* nDAC switch should be set to Chassis to provide proper earthing continuity with a pre-amp

* Setting on the NDX becomes irrelevant, as it is connected via S/PIF, which is galvanically isolated from the nDAC

Correct?

Adam Zielinski posted:

So what that actually means is with a set up like:

- NDX and CDX2.2 connected digitally to nDAC (via DC1).
- nDAC then connected via DIN analogue to a pre-amp.

* nDAC switch should be set to Chassis to provide proper earthing continuity with a pre-amp

* Setting on the NDX becomes irrelevant, as it is connected via S/PIF, which is galvanically isolated from the nDAC

Correct?

Yes.

Ditto    

That same wording is used in the NDS/ND5 manual.    The line "...........switch should be set to floating if one is connected in the system (unless a digital signal connection is used)"   is the problem.

If it's set this way the streamer (NDS) it will not provide a grounded analogue signal to the pre-amp. If the intent is to carry a signal ground on the analogue connections only & have the digital circuit(s) floating, OK.   But that is my question:  it means the streamer (& nDAC) analogue output into the pre-amp is un-grounded.  So why is a signal ground required into the pre-amp when connected to an analogue CD player & also required when connected to a streamer (ground switch set to Chassis) when the streamer is not connected to another unit or to something without a ground.   But then if the streamer is fed by a digital input (S/PIF) then the streamer does not need to have its analogue output to pre-amp signal ground.       I still think Naim need to clarify all the connection variables.

Mike-B posted:

That same wording is used in the NDS/ND5 manual.    The line "...........switch should be set to floating if one is connected in the system (unless a digital signal connection is used)"   is the problem.

If it's set this way the streamer (NDS) it will not provide a grounded analogue signal to the pre-amp. If the intent is to carry a signal ground on the analogue connections only & have the digital circuit(s) floating, OK.   But that is my question:  it means the streamer (& nDAC) analogue output into the pre-amp is un-grounded.  So why is a signal ground required into the pre-amp when connected to an analogue CD player & also required when connected to a streamer (ground switch set to Chassis) when the streamer is not connected to another unit or to something without a ground.   But then if the streamer is fed by a digital input (S/PIF) then the streamer does not need to have its analogue output to pre-amp signal ground.       I still think Naim need to clarify all the connection variables.

Mike - I can assume that only means the setting is irrelevant if using the digital output - and indeed i remeasured it again - and the digital ground is isolated (well a few mega ohms) irrespective of the signal ground setting. I am not sure I can see all the variables as you can or what further clarification can be provided given that the digital signal has nothing to do with the audio signal.. other than perhaps making clearer the SPDIF outputs and inputs are galvanically isolated. Its a bit like the NAPSC - it has earth potential ground - but as it is quite separate to the signal circuity no further detail is required - and  any more might cause confusion.

Mind you as shared on the forum before - if all your inputs to the NAC are floating - it can be quite useful to use a signal output set to chassis ground from the streamer to one of the NAC inputs even though this would be a 'dummy' input if you were using a third party floating DAC - like a Hugo for example fed by the streamer SPDIF... it certainly gives a worthwhile performance boost

S

Simon I concur with your measurements of the isolation of the electrical S/Pdif digital inputs.  I found the same with the ND5 XS.

However I simply don't know if it's the same for some or all of the the more basic components (e.g. the 172 or members of the Uniti series).

Huge - i don't know either but I would be surprised if it were different

Alma, the NDS (NDX/ND5 & nDAC) manual is perfectly clear to me as well. I read & fully understand & maybe that's why I am questioning the way its written. 

The CD player provides the required single (one) signal ground with analogue, that is perfectly clear & not what I'm questioning.

Also when the streamer is used as the only source component it is perfectly clear the switch should be set to Chassis to provide a signal ground to the pre-amp's analogue input.

My question is with the CD player in digital (transport) mode connected into the streamer(s) (& nDAC) digital input(s) The manual it says select the Chassis position unless the DAC is connected in a hi-fi system incorporating another earthed source component. OK semi clear. Then it says Note: All Naim CD and DVD players are earthed so the Signal Ground switch should be set to Floating if one is connected in the system. This is the ambiguous part; assuming the Naim CD player(s) do have a galvanically isolated S/PIF circuit and the signal ground path is not carried from the CD player, then to have the streamer or nDAC ground switch set to floating is not providing a signal ground to the pre-amp analogue input.

Apologies for the typo Alba        ..........  I was also including the nDAC manual as well as streamers,   that does not include the (unless a digi connection .. )     "Note: All Naim CD and DVD players are earthed so the Signal Ground switch should be set to floating if one is connected in the system" . (end)     It does not clarify if the CD player is connected  to a pre-amp analogue input or connected into the nDAC.

I am arguing over how these manuals are written,  not what I do or do not understand,  thats all

Guys, guys...

For those non-native English speakers (like yours trully) - it is unnecessarily complicated. A simple set of bullet points, with clearly written POSITIVE instructions would be much easier.

Example:

* If you have X and Y connected, switch X to position A and Y to position B etc, etc.

 

@Adam Zielinski

I've tried to do something along those lines, evidently with, at best, limited success! 

 

I was actually alluding to Naim, not you your's were clear.