XPS2 or 555ps

Asking for a friend-honest.
If you want to upgrade the PSU for an NDX2 or cdx2?, And had a choice of a s/h 555ps or a newish xps2. Which should you choose?
Or, put another way, is there any difference in the 555s output over that if the xps2?
My friend doesn’t want to spend the modest extra to find that the two outputs are essentially the same. But equally doesn’t want to find out that the modest difference would have been the way to go. I don’t think she will be able to trial both a/b.

if they are both either DR or non DR I would say 555 all day,

having said that I have not compared a 555 non DR with the new XPS2DR, but I am sure on here someone has a more informed view

My dealer advocates that a non-DR 555ps is still some way ahead of an XPS-DR, so if you can find a nice example of a 555ps, I would buy with confidence. I did exactly that some years ago and now have the option to DR the 555 if I want. I’m actually trying a new 555dr at the moment as my 555ps is now 12 years old and I’m wondering whether it needs a service. The new 555DR is better, but the difference isn’t huge on an NDS and that’s verses a 12 year old supply! (to my ears anyway).

So , I would go 555ps if you can - probably would be around the same money as a later model XPS-DR anyway as everyone seems to want DR -which makes the nonDR 555ps a bargain!


That’s usefull insight, and the sort of thing I’m interested. She has not mentioned the option of a non dr555. Currently the new xps2 and pre owned 555dr can be had for similar money.
My first reaction would/should be with the 555dr, but, if we took the tops off the two, what differences would we see between the two with respect to the cdx2/ndx2 output?

If I’m honest, I really don’t take any interest as to what’s being / not being utilised in a power supply with any particular product. I listen and judge by the sound I get as to whether I prefer something or not. Neither the CDX2 or the NDX2 are capable of fully utilising the 555ps, but regardless, my understanding is that (sound wise) it will still outperform the XPS2 DR with these products.

I would recommend demoing or borrowing first and just see what you think. The 555 also gives you more scope for growth ie. NDS, ND555, so if it’s the same money, just a bit older than the alternative XPS, I don’t see what’s not to like! Good Luck…

If can be afforded 555 preferably DR all the way.



555ps even if non DR it makes a fundamental difference.

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I compared several option in a store demo a few years back. The system was CDX2/282/hi/250-2/ Kudos C2 to begin with. First we compared a DR XPS to a non DR 555ps, even with a non DR hicap the choice was easily for the 555ps. We then substituted the non DR hicap for a DR one, to me this was a small gain but not something I’d lose any sleep over not having, then a supercap DR was put in place. The Kudos speakers had been somewhat muddy in the bass up to now but not any more, the system was really sounding rather glorious, however, as my speakers at home didn’t have a muddy bass the choice was simple, get the 555ps on the spot as it was for sale ex demo for the price of the XPS DR and the supercap could wait. In fact it waited until after I’d bought some traded in NBLs and later found a home on my superline.


She’s talking about spending upto £4k ( money she got back from over paying tax last year apparently). So would/ should she get a used regular 555 for that?
It’s these sorts of decisions that keeps me happy with my cd5si and ND5xs2!! ( If only)

I’d not expect to pay more than £2.5k for a non-DR 555PS. A used DR version can be had for around £4.5.

My experience is that the gap between the non-DR 555 and the XPS is greater than the difference between a non-DR and a DR 555.

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That will please her then. Thanks. These PSUs are of little interest to me, hence I don’t know much about them or their pricing.

I just bought a less than one 1 year ex demo for £5k

Not according to Naim themselves, I asked this very question with them recently and they said the XPS DR is superior to the 555ps non DR.
They stated that the DR implementation is a considerable improvement.


Well, I’m sure they know best, but to these ears, I disagree. :wink:

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…I would quantify that by saying I think that the DR effect seems greater on the power amps than on the source power supplies, in my experience. I am currently comparing a 555dr to a 12 year old non DR 555 at home on an NDS, yes the DR is a little better, but I’m not convinced I will be parting with the extra money to upgrade… it’s just not that great a difference to me. Power amps though, I think that’s where things may be a tad different!
Again, just my opinion.

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At least a “massive transformer, 40 percent larger than that fitted to the XPS” says https://www.naimaudio.com/product/555-ps

This equates with my experience on my then 272. 555PS bloated and unbalanced it whereas XPSDR improved everything in balance. More nimble and musical than the non-DR 555PS


I saw that on the Naim site and laughed!
Look at the current delivered by either PSU. Those Txs are already significantly larger than they need to be. I can’t see the source devices that are drawing this current to be fluctuating much. Pretty constant I’d have thought. The Tx is just topping up the caps after the voltage has been rectified. Now, for a power amp whole different issue. For sources?
Anyway, a bigger TX will do no harm.

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I’m not disagreeing. But then anyone who even considers an external PS, XPS or 555, over the internal one of a CDX2 etc. already made the decision on hearing/believing in the difference. I mean, certainly an internal supply can deliver the output needed by a CD player :slight_smile: or even a preamp, and many people love the 555 with the 272, so … In the end, only your friend’s ears can be the judge. However, 555 DRs that are maybe 2 years old or very recently serviced are offered for around 5000.

I’m with you. I get the importance of a good PSU. And one that is well regulated. But, all this can be delivered in the original box. There will be talk about mechanical noise and other things that make the external argument stronger. The regulation bit is the interesting tech. That could be fitted in the cdx2 or ndx2 box. And maybe it is.
The sound test is the only test. Being an engineer albeit mechanical, I tend to want to know what my £ is actually buying in terms of engineered hardware. I can’t help it!

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