nDAC with 555PS DR or 555PS

The exception would be the 252/SC vs 252/SC DR where people here on the forum generally seem to think the DR combo much improved.

Also I haven’t personally heard the other combos with or without DR but it seems the vast majority of people on this forum prefer DR with classic boxes except with NDAC.

They also seem to prefer DR on the amplifiers

@Damien0 Have you tried your NDS with 2 555DR? Maybe it’s even better?

I am not pushing for DR since I have no opinion other than it seems as the old 317 would be outclassed by a discrete solution made by Naim themselves having it incorporated in all their high end products classic and new classic gear all the way up to Statement.

That is defo a possibility, i just remember when i was swapping things around the none dr ended up on the analogue. when i first got the dr psu i started with it being on the analogue side.

If anything id like to change my pre next, saying that i dont really have an itch to scratch, my current setup is the best i have ever owned by some margin

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Did you service the 555 DR or could that have been a reason for the recently serviced non-DR to sound better? How old was the 555DR?

I’ve had both non-DR and DR on most of my kit. I’ve run a non-DR and a DR’d power supply on my old NDac and I do understand the comments a lot of people make. In fact for a long while I didn’t use any external power supply on my NDac and found it really easy to listen to in a very non-fatiguing way. When I started adding power supplies I found that it began to show me the limitations of my source and actually prompted me to buy an ND555 and get rid of the NDac and Node.

That final switch to fully DR’d equipment was quite a radical and revealing moment. The jump in performance should not be underestimated. Suddenly everything started to make sense and sounded very much like real instruments should. It still fools friends who think I have a live band practising in the front room! Adding a second DR’d supply to the ND555 just took things into another realm.

I think that both DR’d and non-DR’d power supplies definitely have their place in the great ‘hifi’ scheme of things but if you are going to push the envelope DR gets you closer to the ‘edge’ than anything else I’ve tried.

I have tried all possible combinations… from non DR to all DR, i.e. source, preamp and power-amp and I think both groups of people who like it and don’t are correct. How come? For me a DR power supply, and I mean any of them brings additional dynamics in a way photoshop does. In Photoshop you can take a picture and increase the contrast. And here is the thing. If you get low contrast picture and increase it by say 10pct, it will improve. If you add another 10pct it may improve again and so on until you reach a point where adding more contrast will make your picture starting to look worse. I would say each DR on the chain does like 10pct. And I would say our loudspeakers are the picture. If they lack dynamic, by adding DR you may get better result, and so keep adding them till sound improve for you. And thus some people are saying all DR is a good thing, and some other people saying no, they are not, both being right from their own perspective. For me best works non-DR source, non-DR 552 and 300DR.

What are you using to feed the nDAC.

It can be just as important as the power supply.

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I think the merits of DR vs non-DR PSs depend on which PS it is as well as which box it’s being used on. When I had an original SuperNait powered by a HiCap I took up the opportunity to have it DR’d and that was the best value Naim upgrade I ever made, a major improvement in SQ. I also had a XPS powering a nDAC done and whilst that was also an improvement to my ears, it was much more marginal.

Oh and the 250DR is just miles better than the previous 250 (he said from behind the sofa!)


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I would like to make a correction, the DR at the power amp had least of this dynamic booster effect if any or just a placebo, though i did not test all possible combinations with it as it was upgrade straight out of the box for me. It is also a different amp (using the new transistors and perhaps other new components. So to be more precise, if I need to attach a number, would say 10pct for source, 10 percent for pre and 2-3 pct for the power amp if any.

I am not an audio engineer so please do not laugh at me, I need some pro help to demystify this DR effect, that concerns many of us. So far, came to the conclusion that some people are happy with the DR at the source and pre-amp and some not, right? Also all people are happy with the DR at the power amp. If so could it be the speakers making the difference. The effect is most noticeable at about 400-600Hz, which is about the mid range of classical guitar. Looking at my speakers, they have a high capacitive load at 433Hz (-41deg phase shift and 6.54Ohms impedance), hmm, could that be it? so how could be and is it possible that the output capacitance of the loudspeaker is fed back into the control loop amplifier and form a single-pole lowpass with the pre-amp output impedance, that further transfers the same effect to it’s power supply output impedance causing phase shift, that further cause instability in the control loop, when there is not enough phase safety margin. And is it possible that in the older non-DR versions this phase safety margin is bigger, so they are less speaker load dependent. On a separate note, if that could be really the problem, is it fair to assume, in the new classic series the power supply for the source and pre-amp was deliberately made non-DR? at least I cannot see it as DR? maybe i am wrong? @Richard.Dane can you help too?

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Sorry BBK, I’m not an engineer. Perhaps if @110dB sees it…?

The NPX300 contains 6 DR regulators.

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Here’s a quick answer, I hope it helps.

NPX 300
The NPX 300 has 8 DR regulators, with 6 separate grounds. The separate grounds join at the appropriate PCB location for the respective product that is being powered. (for streamer, pre-amps and streaming pre-amps)

Power amps
The speaker load impedance irrespective of a regulated PSU in the power amp will have an effect on the performance. Power amps have feedback, the feedback is taken from the output. Loading on the feedback changes the phase shift of the feedback. Engineers in all companies work hard to ensure there is adequate ‘phase margin’ for closed loop stability irrespective of load. Lots of compensation is great for stability but makes the amp sound dull, too little compensation sounds great but could be susceptible to very high frequency parasitic oscillation (typically 1-10MHz region). The PSU of the power amp and power amp output stage appear in series with the speaker signal current.

Certainly the high frequency impedance of a power PSU will effect stability. Detailed circuit and PCB design is needed. Simply adding capacitors on the power amp rails lowers the impedance but can push noise into the ground they are connected to. At Naim the connection from the built-in DR regulator is connected as close as possible to the power amp output stage.


I’m sure DR is superior to non-DR technically but after having a non dr 555ps on my NDS and the pleasure it gives me as the joint best sounding source I have ever heard (with myLP12), I cannot imagine ever wanting to “upgrade” to DR. Perhaps it’s just the 100% or more premium for used items or the eye watering cost new (for me)? Certainly non DR is for me is not wanting in terms of SQ. I do however find it very interesting that some prefer DR and some don’t. There are obviously many parameters at play here but I am a firm believer in having a balanced system and that such a system can in many cases compete with the best of the current technology on an even playing field. Of course some will disagree :nerd_face:

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Dear @110dB , Thank you very much for your time and input. As far as my brain cell can understand, the better the PS is the more critical is to the loudspeakers load, and that could be one reason for the “DR effect”. I am happy with my DBLs and a non-DR versions, think this will end the discussion for me :slight_smile: and hope will also help others in optimizing their systems going forward. I think people with ND555 have greatest flexibility and luxury to have one DR and one non-DR and swap them to find the best SQ.


@IainO , thank you for the input too. Given the conclusions so far, would be better to also have NPX300 without DR regulators, so people can, can have options :slight_smile:

@Paul52135 , if your source is better with non-DR, I think your pre-amp would be also be better with non-DR. I wander which you have at the moment?

My preamp still has its old 52PS :grin:. I suppose it’s possible to DR with a Supercap DR but I won’t be trying it. I wonder if anyone else has?

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I stand corrected by Steve on the 6 vs 8 regulators.

I said 6 because that’s what naim’s own (old) website used to say, just check google

It’s also on many reseller sites, such as Sevenoaks….

You can see 8 regulator boards in that pic.

So it seems naim have shot themselves in the foot by releasing launch materials which were incorrect! Now all over the internet as 6…

Marketing and R&D are two different universes these days.