I recently got my set of three Nap500 re-capped and upgraded to DR two weeks ago. They were eight years old so I was going to get it done in the next year or two anyway, but hearing friends DR update performance-lift in passive systems I was suitably impressed and wondered how it would sound in Active use.
Last year I purchased the S1 Pre which was a large upgrade in performance from the 552 I had been using. Add to that the full loom of SL leads I got at the same time and I’ve experienced a large lift in musical performance already – I was wondering if I was being greedy, the answer is obviously yes! 
I’ll leave aside the painful run-in experiences, aside from that I really needed ten days warm-up to get from variable ‘HiFi’ sound to music-making. There is still run-in going on, which manifests as a meandering sinusoidal increase and decrease in performance over time, but it has settled enough to get some first impressions.
I’m very pleased and impressed with what the DR does. There is a lift in clarity and removal of ‘gaps’ in the resolution when music becomes complex or loud – it was as if before things gently smeared-out the resolution at transients. This is especially noticeable on drums and bass guitar notes when played fast. Now there is more power and definition on busy riffs that was not there before.
Overall the Amps produce a bigger and brighter picture of the performance – a larger window into the musical performance.
For example, on the old Renaissance ‘A Song for all Seasons’ which is a complex Prog-Rock with Orchestra, guitar, synth and Annie Haslam’s powerful soprano vocals the album becomes a live album! A friend who knows the Album well and my system, was convinced I’d swapped the CD for a live version – I had to extract the disk for his scrutiny before he admitted it was the same old CD. That particular CD (an old version) has large dynamic range and a lot going on that is now beautifully rendered with clearer insight into the performance and Artist-intent than I’ve heard before.
Overall the DR 500 resolves lower frequencies better and has lower distortion in the high frequencies. The LF does seem to have a lower roll-off point too – it is more seamless and fulsome in a good way. This matches what the S1 Pre did, as that also took the bass performance much lower with far better power and control. The combo CD555S (2x555PS)- S1 Pre – 3x500 DR with Ovator S800 works together beautifully as a system in my opinion.
The usual question is – ‘why don’t you go Passive S1 Monoblocks instead of Active 500DR?’
They are different systems in what they each do well and I prefer what I have done along the Active path.
I’d love the S1 Monoblocks as they are beautiful and in a different league to the NAP500 even with DR, but you still get the passive effect I don’t like – a gentle smothering of the dynamics and immediacy of the performance that is portrayed so much better Active. I can’t afford a set of four S1 Monoblocks - love to but can't.
Back to the DR 500: It is difficult to properly describe what I mean by grater ‘clarity’ - I'll try. The reproduced note-structure and power of both voice and instruments is as if they are playing inside your body at times – I’m not meaning playing loud, just more clarity and power in the harmonic structures with less smear.
And the system does go a lot louder with less dynamic ‘cloying’ at the edges – it is clean, clear and fulsome. One thing I like about a good Active system is the removal of dynamic effects of one part of the music treading on another – this is done much better now.
In short – if you are dithering about getting your NAP500 DR updated – get it done, funds permitting. 
My thanks to Naim for turning it all around in two weeks and my Dealer, Signals, for making it all happen.
DB.
Posted on: 14 August 2016 by Allante93
DB,
As impressive as your system is - and 'envy causing' of course (!) - do you feel you are missing something extra special by not being able to play 24 bit 192kHz?!!!
Even in my modest system, the difference between a well recorded 16 bit 44.1kHz and its equivalent 24 bit is easily noticeable.
Consciousmess - I don't think this is quite so straight-forward. I've heard and have some very disappointing Hi-def recordings which have been significantly bettered by red-book CD. The critical thing seems to be the quality of the mastering.
On the sidelines, but spot on!
I know a gentleman, on this very Forum, who has been blessed with both formats, an Loaded LP 12, and a CD555, this gent prefers the LP-12. But guess what, when a particular cut isn't available on Vinyl, he has to resort to the CD555.
As been mentioned a number of times, A new Paradigm, no longer, just the Analog TT, Digital CD, and Digital Streaming, but a choice, depending on Music & Mood!
The 282 Active Club, Please keep the sidelines informed, nice hearing from you DB!
Allante93!
Posted on: 26 August 2016 by Darke Bear
An Update:
After week 3 of run-in things improved significantly and now it is nearing week 4. A friend visited in the second week of run-in and we both heard the run-in like clouds of haze over the music moving like patchy fog when driving at night. Clear patches of 'special' performance then duller and ‘normal HiFi’ performance. But after 3 weeks the threshold of this seems to have dropped and although I still hear run-in effects, it is now not intrusive into the music for me.
The presentation is markedly different from what I’d become used to over many years with my old NAP500 Amps. It is not just clearer but the music I is presented differently in ways difficult to describe, but I’ll have a try.
First the Bass performance is fundamentally changed, to the extent I wonder if Naim are now using the Statement developed DC-offset management system rather than the old servo-loop the NAP500 had before. There is a quality of ‘there-ness’ (new word) to the bass now; it has a different presence and does not appear to have the very low-frequency phase changes that the old NAP500 had, which I never really knew it had – other than when they are not there, like now, it is obvious!
There is a clean, firmness and power available in a different way. Things like large kettle drums have real feeling of a wedge of air whacking the room that was not present before. Bass chords go deeper with more clarity and separation – a lack of murky noise breaths extra life and vim into playing. The formerly lazy bass guitar is now played by a man possessed!
This lack of noise and phase distortion in the low bass puts a darker and more intimate perspective around the performances in many cases. You now hear what the lower vocal ranges of singers does with greater clarity.
There is also much more body to instruments and a fullness to the sound that is pleasing. The dynamics are cleaner at the highest frequencies too – if a vocalist screams in a live concert it is very loud and clear!
I’m also finding that I’m experiencing the music much more in my body now than before, particularly the chest – this was a surprise. This is not because I’m playing it louder – in fact I’ve turned it down until I get more uses to the effect. It is as if instruments and vocals now get a stronger sympathetic reaction with all the parts in you that can move. It puts more into the concept of ‘being moved’ by a performance. I think it is the extra harmonic purity and power therein of the notes, for the same volume setting – before the power 'spread-out' and ‘filled-in’ between the notes, but now it does not spread and is contained in the musical notes.
Things like Synth and Organ music are really taken a long way forward. Vocalists can really connect with you with no effort required – there is no ‘listening to the music’ as much as a connection with the performance.
It is still running-in and I’m confident there is a lot more to come, but I’m pleased in what I’m hearing right now.
DB.
Posted on: 26 August 2016 by Darke Bear
Yes - I like the way it is going.
I've obviously heard the lucky people's systems that already had the NAP500 DR upgrade and was suitably impressed at what I was hearing. I've not heard a report of its use in Active systems yet, so was interested about what it would do.
I'd already heard aspects in the high frequency performance in those passive systems that were very similar to the upgrade I got when going from 552 to S1 Pre - a smoothness combined with easy clarity and lower noise. These are indeed present in Active mode and more! There seems to be a synergy with the S1 that I'd hoped and expected, but good to hear. Naim obviously designed it to work well with the DR 552 - which it does.
The 500 DR sounds ... nice! 
A little word that sometimes is hard to achieve in HiFi with all the other things you want as well sometimes being hard to juggle and fit into a synthetic whole.
It would be good sometime to hear what other users make of the NAP500 DR used Active.
DB.
Posted on: 27 August 2016 by Darke Bear
Thank you DB for qualifying something unquantifiable! I'm still mulling over if I should get my 9yr old 500 (passive) serviced and DR'd and your experiences are making the decision for me!
All the other passive systems upgraded that I knew well for many years were improved to a higher level of musical performance afterwards - it is what tempted me. I was otherwise going to leave it another year or two, as I'd wanted more time to recover from S1 Pre and SL Loom last year, but what I heard was very significant, so I wanted it.
Run-in is less ruthless passive as Active amplifies both the good and the bad in a system, so passive tends to have, from what I was told, an odd off-day or so and not the off-week or so.
Yes - go for it funds permitting. Mine were about 8 to 9 years old and I could have run them another few years from what I heard was my previous plan. But I have a finite life and want to enjoy as many things of musical Art as fully as I can, so having it now was obvious.
One thing I'm still mesmerized by is the revelation of the rich textures in the harmonics of bass guitar and synth playing - there are so many new musical interplays that the 'open-mouth' gawping really happens. The whole thing is a beautiful synthesis with what the particular strengths of the SL cables do too, so you will probably want to listen to these if you like what the DR does.
DB.