2x555DR vs. 1x555DR on a ND555

What do people who have two 555DRs on the ND555 think - compared to a single 555DR. I’ve got two - but not 100% convinced yet. Seems like there’s a tonne more detail, transients are faster, a lot more upper frequency detail etc - but when I take the second PSU out, not sure whether I really miss it…

@Darkebear ?

It is always a personal decision in context of the rest of the system and one’s own taste in presentation.
I prefer two supplies - no downside for me.
But some do not like the wider sound-stage effect in systems it may be too much bass energy or too much top-end energy.

I’ve found that set-up is very important more so with the two supplies. Mains plug-in sequence is also important - try onto dis-board the sequence (from wall socket): Pre - 555PS(Analogue) - 555PS(Digital).

But you go with what you prefer.


Correct me if I’m wrong - input closer to analog out is analog? And that PSU goes to the top? Or bottom?

Yes - Analog lead has two stripes nearest ND555 Analogue out - Digital Burndy one stripe.

I prefer, when stacking supplies, the Analogue PS on the lower position and Digital above it.


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I prefer it with two: I don’t find the increased dynamism, microdynamics, soundstage, bass definition and instrumental detail make the ND555 any less involving - indeed, quite the reverse. Adding the second PS is what really swing it for me vs. the CD555

I guess those who use two supplies with their 555 will prefer it - otherwise they wouldn’t have spent the extra £7,000. If you think things are just as enjoyable with one, there is no point in having two, irrespective of what others might think.

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Is the addition of a second supply onto a ND555 similar to the effect of adding one to a CD555? There was mixed opinion on the benefits of adding a second supply to the CD player.

Similar but, ahem… different. I found it entirely positive on the ND but stuck with 1 on the CD

I am surprised that no one has taken the 555Ps and just split them and added an extra transformer and case, that way you dont end up with loads off bits inside not being used but still being powered up. Plus i guess that would be even better as the parts are spread away much more, as i take it the main gain must come from the extra transformer as separation is still the same? As both sides are still being powered in the one box, its just that you havent got a cable connected to it???
Seems a massive waste to me and unnecessary cost.
Maybe naim should bring out a special twin power supply for the ND555, NDS and CD555 ? But i guess that would be bad for profit, but then maybe more people would go for it, as i would

And where would they put the second transformer?


In the extra case.

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Double the height of the case?

There is not a lot of space IMO.

Also the only bits not ‘used’ in the two supply config are half the DR regulators on the left.
The rest is used and Naim have said the main benefit comes from lower noise from the dedicated transformer for the separate Analog and Digital supplies.

90%+ of the cost is the box and transformer and assembly costs, so no point trying to save by removing half the remaining 10% IMO.


You could have a 555DR-A version and a 555DR-D version with optimized circuitry for the analogue and digital supplies and sides of the ND555, NDS and CD555.

Perhaps - but perhaps not a lot.
When there is no load on the non-used supplies when not connected they essentially turn-off and probably make very little difference being dormant inside the box.

All the regulators are star-wired for mains-side connection to the high voltage un-regulated PCB top-right and so it is simpler to consolidate costs into one power supply box that at least has resale value to most people that want both supplies.


The cost of developing to release to market has to be considered too.

The reason the 555ps is still called the CD 555PS is that to rename it would require a complete round of certifications etc as it would be seen as a new product to market.

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Indeed, and that would require changes to comply with current energy efficiency standards. That would probably be the addition of a SMPS for standby mode, as in the new streamers, which would be an increased cost, and potentially a performance hit. So all of the current range of PSUs are probably living on borrowed time.

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Naim…first of all is a business company…2 ps is a better profit

The second 555PS onto my NDS was a big improvement for me. I was surprised by the performance boost to a streamer which I already regarded as perfect. The reason that my ND555 has two PSs is because they are what came off the NDS. I don’t know how the ND555 sounds with a single PS. I think it would still fall broadly into the category of bloody marvellous. But that’s just a guess.