I don’t have a DC blocker and haven’t yet investigated the topic as I am lucky to have no issues with transformer hum. @conlegno above is less blessed and forced to know more about the topic. In general, it is a complex issue and hum can have many different causes, which consequently require different solutions. (E.g., in cases where hum is caused by mains pollution coming from a different tenant on the same electrical subnet, not even a dedicated mains in your house may help). There is a great thread going into all the annoying details here:
I have a Nova in our lounge and it always runs warm to hot when playing at a decent volume, nothing to worry about I feel. I have a Powerline on it and use A Isotek power strip that includes power filtering, which improved the clarity and reduced the noise floor - we have reasonably “noisy” mains.
Now be warned. That was the main system and it replaced an UnitiQute2. I like music loud that you can feel, with detail and without distortion. I upgraded to a SN2/NDX2, then added the power supplies. Now I have a used 252 using the SN2 as a power amp until a new 250 arrives. So, mind that rabbit hole and maybe enjoy what you have for now.
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In airedog’s case, it shut off due to heat protection - at least with the previous AQ speaker cables. So that was worrisome, which is why we talked him into trying with NACA5. I don’t think we can say yet if this made a difference to the shutting off.
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Well…phew…no hum here…thankfully.
Correct. Yesterday as I was grooving and feeling the music (lol) I chickened out and used the fan as it was getting pretty hot. Does our hive here think today I should give it a run without the fan? I could play the same stuff as the other day when it shut off. I was hesitant to do that…afraid of damage. But Sued said it’ll shut down before damage happens…where’s Clare? She hasn’t poked her head in here in a while…
I am convinced that the heat protection is there to kick in before damage occurs. At least in the amp manual for the 300 it states:
So if it was me, I would just try with the fan. If there is no difference to the AQ cables, at least you know. And if you talk to Naim support (which I would do: support@naimaudio.com), you can at least tell them that yes, you tried with NACA5 and it did not change.
Clare has not answered here because she has not been part of the discussion in this thread. She participated in a parallel discussion of the same issue in another thread, around here:
Based on this comment by Clare, if yours still shuts off even with NACA5, I would definitely ask support@naimaudio.com if this is to be expected
Well I do think the cables made a difference, it did seem to not heat as fast or as hot. But it did get hot when I was pushing…not as hot probably, but hot. About fan vs no fan, to push without the fan would tell me because the fan eliminated the problem with the AQs. The NAC A5s as I said, I believe, improved the sound. I do really feel good about the Nova; I did make the joke ( on that thread) that the Nova will be my last purchase! 
but I think it’ll keep me happy until I get my boat in the water anyway… 
Yeah, like I said yesterday: If it now gets hot but does not shut off, I would consider it an improvement and would think it’s fine. The thermal protection will hopefully know when it has to step in.
You will only know when trying without your big fan, I guess. If it still trips the thermal cut-out, I would definitely speak with support@naimaudio.com and ask them - because it doesn’t do that for Clare according to the above comment, even if driven “VERY hard”
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Right. Later today I’ll give it a run.
I’ve been at @65 for an entire album, barely warm, no fan!
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No, I think this always existed, but I think it is displayed only in the full view (after clicking More at the bottom of the preview). It’s pretty cool but only exists on iOS, sadly. No such thing for us Android users 
Ha…I give up! Simon and Garfunkel at 65 just made me submit! Still barely hot. Yeah…the cables are making a difference. Plus Apple Music Hi-res kicked in today…
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Glad to hear that NACA5 is making a positive difference.
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Yes. A clear difference. And, I just plugged the Nova straight into what is a dedicated circuit. Another clear step up. Geeze…I was doing 70-90? no more…right now 60 is blasting.
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OK…I was cleaning so I put on Afro Celt SS at 75, when finished I checked…the Nova is quite hot. Didn’t shut down, again my ears gave in. And without fan. Nor Powerline. But direct in wall as noted. Sound is pretty darn spectacular.
With the NAC A5 cables and now plugged direct, it’s louder. I don’t know I’ll hit 90 (granted that was a short burst) again. Or 80. 75 now is crazy loud. I peeked sheepishly out the front door to see if neighbors were gathering with pitchforks.
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Hello, i’m here - was busy doing the day job (I’ve actually been in our demo room having a lovely long listen with a reviewer - been a long time since we’ve been able to do that!)
Glad that cables and a direct mains connection has definitely helped matters - sometimes less is more!
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Do you think the Powerline will also help with heat? Though, I’m at 56 at the moment and it is not too hot at all, so really it’s much better. Fine product! Really. For me, a guy that crawled on my hands and knees for a living (flooring installations) that’s a significant expenditure. So far tho, I’m thrilled. I wondered if it was unnecessary as the Atom is a fine unit which sounded great with the Choras. But…I had no idea the Choras could sound like this. I really thought it would be glaringly apparent I was under-speakered. Not true. They have handled whatever I’ve dared throw them…with aplomb
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