552 and ND555 inputs questions

I queried Naim regarding which inputs to use on the preamps if using 1 source such as an ND555, whether or not unused inputs should be disabled or enabled on the ND555 and finally, whether “server mode” should be on or off if not using server mode.
I received a prompt reply from Flynn who also gave me permission to post on the forum.
I assume this applies to all pre-amps and streamers.

Thank you for your email - I’ll take your questions in turn.

  1. we recommend for only one source that the ‘CD’ (input 1) input is used as listening tests have proved this is the best sounding input on our pre-amp range.

  2. disabling un-used inputs on the ND555 will make no difference to sound quality, but it will make navigating through the app and ND555 easier as you will only have the inputs you use available.

  3. No, if you are not using server mode, keep it off, it will consume much more power while it is on and in turn will create a noisier signal path for audio.

I hope this helps, please let me know if you have nay more questions.

​Kind Regards

Flynn Charter


On my system the “CD” seems to be mapped to “input 2”.
It corresponds to what’s on the Preamplifiers Connection Guide


Well, that’s put the cat among the pigeons about ND555 input settings! Even the Martin Collums review in Hi-Fi Critic stated that Naim recommended having all inputs enabled improves SQ, although he confessed he couldn’t hear any difference in his system.

Incidentally the CD input on my NAC 552 is also set to Input 2.

Mine is exactly the same as yours with input 2 to CD as per the list but then again I’ve never bothered about re-assigning any of the inputs. How do you assign input 1 and I wonder why Naim leave it unassigned if it’s the best input? Am I also right to assume that the inputs are all essentially flat without any tailoring? I admit to preferring my tuner input (3) to CD input (2) with my CDP555 as it seems to have a slightly richer and warmer sound. Input 2 I find sounds a tiny bit leaner and less extended. I’ve no idea why? I think I might try input 1 when the system goes off a bit. At the moment it’s sounding so good I’m loathed to touch anything.

I think page E3 of the Preamplifiers Reference provides all the needed info.
Hope it helps.

As for me, I’ll leave it as is : input 2

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My Input 2 is also CD.

This is all now as clear as mud!

Flynn probably just mixed up those inputs.

I will e-mail later tonight for clarification regarding input 2 versus input 1

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It would indeed be interesting to know if we should or not follow the Connection Reference Manual.

Should that Reference Manual be updated?

It makes for a lot of permutations to try when you can assign sockets to inputs, assuming they all sound different and then there’s where to park the (muted) record selection. I’m using socket 1 assigned to hdd for ND555 and 6 assigned to AUX2 for superline as it gives the best clearance for the cables. I have the farthest RCA (unconnected) assigned to the CD button from when I was experimenting with where to park record and I did have a slight preference for parking it there but only for the first 20 minutes of each session, after that parking record on AUX2 seems preferable so that’s where I leave it.

Quite … I connect my Naim CD (CDX2) to the CD input 2 on my 552 and my DAC to my assigned input 1. (And usually my tuner to input 3)
Both sound sublime, and automation works well without me having to faff around much.
The key thing for SQ is to ensure there is one and only one input connected that is earth grounded.

The disabling unused inputs has always been a usability thing… it possibly was a subtle SQ thing very early on with the legacy streamers with very old firmware I seem to remember from my early NDX days… but absolutely no impact with the new architecture and products,

CD555 here also goes into input 2. Input 4 for AV in bypass mode and 3 for a portable DAC if I want sounds off the iPhone.

Funnily enough, I only recently discovered that the 552 auto switches to input 2 when you press play on the CD555. I’d always selected it manually before that. :man_facepalming:t5:

Oh well, as they say - everyday is a school day! :grinning:

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Sounds like you have AIS (Auto Input Switching) enabled.

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FWIW, I’ve always had my CDS3 or latterly the Naim DAC connected to Input Socket 1 on the 552. I have no idea whether I could truthfully tell the difference between socket 1 or 2, particularly as I have just about input filled on my 552, but past wisdom favoured 1 for a single source so that’s what I have always done for my main digital source…

Has that alway been available? First I’ve heard about and don’t remember my CDX2/282 doing it.

It has always been a feature of the current range of pre-amps. details can be found in the manual, here:

14.1 Automatic Input Switching

With Automatic Input Switching engaged the appropriate
source input will be selected as soon as any handset function
for that (Naim) source component is operated. For example, if
the tuner input is selected and the cd play key is pressed on the handset, the preamplifier will automatically switch to the cd input. Automatic Input Switching can be programmed to operate on any combination of the cd, tuner, av and hdd (NAC 152 XS only) input buttons (and sockets to which they are assigned).

To enable Automatic Input Switching, first switch the preamplifier into program mode by pressing and holding the handset prog key (with the handset in preamplifier mode). The front panel mon button (NAC552 mono and NAC 152XS mute buttons) will illuminate if automatic switching is already enabled. If it is not enabled it can be switched on by pressing the same button.

With automatic switching enabled, pressing the button again will reveal the inputs selected for auto switching by their indicators illuminating for a short time. Repeated operation of the button will sequentially select through each possible combination of cd, tuner, av and hdd (NAC 152 XS only) inputs and auto switching disabled (all indicators off). When the desired inputs selected for auto switching are indicated, stop pressing the button.

Automatic Input Switching only becomes operational on exit from program mode by pressing and holding the handset prog key.

Note: The preamplifier will leave program mode automatically if no control commands are received for five minutes.

Note: In a few cases some further equipment configuration may be required for auto switching to operate correctly. Please contact your retailer or local distributor for advice.

Who reads the manuals?! :wink: Only joking. :smile:

That’s useful info, just need to set up socket 4 for the AV2 as that and input 2 are the ones in main use.

Cheers, Rack.

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This is what I thought.


All I can say is that the opposite recommendations were made 1 year ago. The Nd555 Hificritic review by Martin Colloms pointed that Nd555 sounds better with all imputs enabled.
Naim at that time recommended that too.

Perhaps you can just try if it makes difference, and keep the best set up for sound quality.

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Actually I believe that Martin Colloms said that while the Naim rep recommended all unused inputs be enabled, he couldn’t discern a difference in SQ

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