Just remember that some people are relaying their success using older generation kit which was launched pre DR. There are quite a few accounts of non DR 555’s being preferred on the NDAC over the DR version for example.
It would be interesting to learn of people’s experiences with the 2nd generation kit which was designed with DR in mind from the beginning.
As the ndx doesn’t use all the power lines a 555ps has to offer, so in effect you are wasting part off it, plus a dr power supply has much better regulation boards over a non dr power supply, i would certainly go for the xps dr power supply.
As apart from a bigger transformer in the 555, that you’re not using all off it anyway, what else is different apart from the separate burndy cables, which again you will only use one?
People are very quick to spend your money and always go big, but even naim say xps, so once again that’s what i would do
That’s true, but you are already wasting all of the internal power supply in the NDX. This is just one of many redundant parts of a Naim system which are an inevitable part of the upgrade path for many.
Some people seem to lose sleep over this. Best to just judge with your ears in my opinion.
I agree, but can’t really see what gains will be had over a xps dr, as the gains to be had with a 555 is the separate burndy cables, more power lines and with this a larger transformer, 2/3’s of this you won’t use ever on a ndx.
Plus throw in a non dr into the mix and can’t see why you would want to go that way at all ?
I think I posted about this a few years back but to summarise, when I tried a 555PSDR against 555PS on my nDAC, I preferred the non-DR version. The DR version seemed a bit ‘too much’ . But, at that time I was running a 282/SCDR into 250 (non DR). A few years later after the 282/SC had been replaced by 552DR and the 250 replaced by a 300DR, I tried the DR version of the 555 again and my preference was reversed. I concluded that there was some synergy in a number of components in the system being ‘DR’, plus the 552DR and 300DR was much more capable of handling the extra information that the 555PSDR was allowing the nDAC to produce.
As always, trust your ears rather than what seems logical.
Hypothesizing and trying to quantify this stuff never works for me. Not that it’s wrong to try to figure out how things work (you could even say the same thing about networking 
) but I suspect the only meaningful answer will come from listening tests.
While I agree in general, for regulated amps it’s different.
I have no idea, and don’t care, if my CDS3 uses all of the power lines available in the 555ps,because the improvement it brought to my system, over and above the XPSDR level, was worth waiting for.
BBWan has indicated that they can source either PS for the same cost, so I’m not sure where the “People are quick to spend your money” accusation fits into this particular discussion,
Paul.
I recall auditioning, and rejecting my dealer’s recommendation of a HiCap upgrade when I had a 202/200 combination as it was just “too much”, but when I changed the 202 for a 282 the HiCap actually refined the sound in a very melodic way and was a very obvious upgrade.
It is all too easy to upset the balance of a system with just one component change, even the obvious or logical ones, so if you can’t pre-audition, be prepared for disapointment 
Paul.
I think it’s the same single Burndy in both options. Certainly with the DR versions, the 555 is quite a bit better with my NDX2 than the XPS was - more refinement and resolution being the game changers. But I’d only go second hand for value for money at a system level with the NDX2.
That’s interesting and in line with my thinking. I’m yet to be convinced of DR in all applications. Yes it made a difference on the NAP300, but that doesn’t automatically mean all DR will be better, at least in my head and half the fun for me is trying things and finding out for myself, but it’s always good to get other people’s take on it. I do realise that the larger part of this forum seem to prefer DR, with the odd exception, 555nonDR with nDac being a notable one.
Oh and it’d definitely be second-hand (I definitely couldn’t justify £7500 on a new one) and both the 555non-DR and XPSDR seem to be around £2500-3000, it’s just that there are far less 555s.
I did the same too, l bought a 555 ps non DR and it’s absolutely caned the XPS Dr to my NDX2, lm now tempted to know if an even further improvement can be made by exchanging the 555 ps for a 555 pd dr, the trouble is demo units are in short supply and it could prove costly if l just presume a DR unit would be better
I assume the early nap 250 is regulated and the Classic nap250 isn’t? I believe it’s recommended service interval is 12-15 years
As far as I know, all 250 are regulated. See this thread
I know the recommended interval is now 12-15 years, but my main point was that you can’t really rely on regulated amps working well longer than that, and in particular can’t rely on them failing gracefully when they eventually do
I’m tempted to chop in my XPS DR for the 555 DR. Seen some lovely examples of late, only a year old for around £4,500 
Yes, all NAP250s from the first to the present day are regulated amplifiers
Are there components to replace in addition to an unregulated amp?
Yes, the tantalum capacitors on the regulator boards. These boards are the power supply for the amplifier boards.
Thanks!
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