I could arrange to let them be send to the service point directly … But - if anything is going wrong (e.g. during transport) it will be better to be the first in line.
Will ask the seller for outside look and maybe humming of PS of both pairs.
Hi Drago,
I was referring to the nonDR 300. Yes the 300 offers more detail and more bass (or perhaps a warmer signature) but I wouldn’t say it was as well controlled as the 135s. The 135s have more power and it really shows. The leading edges are more visceral and defined. More PRAT for sure.
I’ve gone from a 552DR to a late 52/SCAP olive. This may be very controversial but I think the 52 tracks the beat more clearly than the 552DR in my setup. I lived with the 552DR for 1 and a half year so I remember the sound very well.
Now I’m sure in an all 500 series system the 552DR would really shine. However, with the 135s the 52 really does pound out the PRAT in spades. This combination is very entertaining and I’m sure you will enjoy it. The only thing I’m missing at the moment is the bass the 552DR offered. It also offered a lower noise floor and a warmer/liquid signature which IF I have to, I can live without for the sake of PRAT.
Perhaps my 52 head unit is in need of a service, as I don’t think it’s been serviced since it left the factory in 2002. Anybody done a 52 head unit service? Was there much difference in sound quality?
Complete service with POTS 8 upgrade -significant improvement in all areas- quieter too.
AV Options did mine
I also use 135s- serviced by same.
Makes music
David
Hi, I would imagine the pots8 and service upgrade together makes it difficult to determine what the improvement is down to. Wouldnt you say?
Hi khan,
Thanks a lot. Do you still have your 135 in your current system today?
The pots 8 update is already implemented in the late series. It is not needed for your unit. A recapping service should be possible but from all I have heard is a Little tricky for the service people due to the double layered technical layout.
Hi Khan,
The 52 is so good - I have read of some people preferring the 52 over the 552. I have never heared the new one. It is a real compliment to naim, that the piece from 1990 is still so good 
Do you still have the 135s?
If so - that would be my future system
As others have said go for the most recent 135s; if you have the inclination to go active do it now with the other pair. Extra Fraim space can come later.
I ran active SBLs for 15 years before moving to S600’s, still active with the same 135s. In short you’ll have a lifetime’s enjoyment from them.
correct- since both done simultaneously, cannot tell which contributed more to the overall improvement.
It was always recommended by those on this forum, that POTS 8 upgrade worthwhile.
Enjoy
Yes, I’m now all olive for the amplification. NAC52, S’Cap and 135s. I wasn’t aware of any complication in the servicing for the 52. I’ll look into it.
The only thing I’m trying to accomplish right now is a warmer signature which I think I can tweak from a change of tubes in the Audio Note DAC 2 and perhaps integrating a couple of RELs into the mix. I don’t want to let go of this setup as I’m loving the way the pace and rhythm just flow in the music. It’s very involving and I remember that’s what I preferred about the 135s over the nap300 as well.
Hi
Getting closer to deal signature
Is there a problem with humming sound for the 135 present. Will be my first buy without personal testing before (Fine with social distancing).
My current system is absolutely silent - only now and then the 250 hums for a very short time. The 250 I had before had a constant but no noisy hum.
Need your help with connection … 
Googled a lot to be prepared.
I need to connect socket 4 and 5 of Supercap (both stereo, so no specific left/right channel - correct?) with 135. At 135 side I need to connect each one of the XLR plugs (one one the left and one on the right). Speakers need to match with 135 channel - of course.
But how do I know left/right at the supercap end? Is there no channel specific connections as the sockets are stereo?
Left to right does not matter at supercap
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DIN-XLR (Green band) to ch1 (left) on 135.
DIN-XLR (Red band) to ch2 (right) on the other 135.
Note that the speaker outputs on 135s are not ‘mirrored’ i.e. black (-) to the left, red (+) to the right, on both amps (looking at the rear).
Thanks so much.
I have seen that the speakers are not mirrored. I do not want to do any brazing with my cables so I need to turn around one Naim plug (on naca 5) by 180 degrees.
Will do it with the lower one in Fraim.
Do not hope to have max cable terror
Has anyone a humming problem?
Hello,
I have an “old system” too and be very satisfied.
The combo 52/135 do the job very well with plenty of PRAT.
I think the 135 will take out the best of your SBL.
To my eyes, it’s very important to take care to the homogeneity of a system and do not hesitate to recap.
Enjoy because the quality level of the 135 is still at the top!
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We recap our 135s every 6-7 years and have found it beneficial to do so. We really notice the improvement after each (Naim factory or Class A) service, even though the capacitors are far from dying.
Best regards, BF
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Do you hear a huge difference after 6 to 7 years?
My last update was after 15 years and I heared it in a second. It was even that I did not really recognized the 52 to be huge step over the 72 but when recapped 250 was in place all lightened up.
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Hi Drago,
I find it tricky to interpret terms like huge or night & day.
After 6-7 years, the 135s start to lose their grip over highly dynamic, transient basslines and also start to sound perceptibly less smooth or more grainy.
A service soon whips them back into glorious shape though.
Hope that helps, BF
On the other hand, there are people who say that 135s have the ability to last longer before they need a service; 15 years or so. This ability also being shared by the NAP180.
I don’t know what the technical reasoning is around this.
Maybe it depends how the 135s are used, demanding speakers may cause them to run hotter than the fans can adequately cool them perhaps (?)
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Although the 52 is generally regarded as a far better preamp compared to a 72, there is a lot more inside a 52 that can degrade, go wrong or need retrofit improvements, so it’s possible a tired old 52 in need of attention can actually sound a heck of a lot worse than a good on song 72.
I find the simplicity of a 72 has the potential to keep it sounding sweet for a fairly long time.
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