I’ll take a look at sockets when back. On bike right now.
From memory, didn’t hear with 322s.
The whole only lh channel is odd. Will take a close look at rcas later
To me, that says its the 72 - not the Cards… 
I’ve got a few more ideas that I’ll try.
I’ve got a third system ( same as second, without P6) that my son uses. The 72 in that has the links in and no cards, but…
You seem to have THREE 72’s…?
No. Just the two 72s. One with 323Es the other with links.
The main system is a 282. With 2 HCDRS.
I could stick the “noisy 72” in place of the 282. ( I’ll do that next)
When I started on the thread, I thought the answer was obvious to other forum members and just eluding me. I even consider myself quite methodical at fault finding!
This is almost a bit of fun and a good challenge now. But, my wife is trying to work out why I keep taking this " black box thing" apart.
Where I’m at now ( subject to change at a moments notice) is the cards are fine. The 72 may also be fine.
The thing driving the noise is external to the 72. It could be the HC or the 140 or some cables…or, 2 or more coincident faults 
Of the 6 shoe boxes, 5 have been sent to Sheffield by me in the past 9 months. The HC that is in the noisy system was serviced in Sheffield 2017?, by its previous owner.
I guess I’m fortunate to have a few spare naim boxes to try. But getting them in/out of racks, plus the wife and kids continually asking what I’m up to takes the fun out of it! And tripping over Xmas trees.
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Some logical substitution should lead you to the problem…
I suspect it will turn out to be something simple.
Yes. Just not sure yet.
Noisy 72 plus cards in place of the 282 is not noisy. Even with volume pot wound right the way around there was just regular hiss.
Full test not an option with family watching some old tosh on TV.
Since you have another 72 available the obvious next step would be to slot the other 72 into your system then after a quick check that everything is ok, fit the suspect cards in it.
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OK. Thats very useful. So… its NOT the 72 & its 323 E boards. It is the ‘system’ that is was in.
You said before, that touching the case work (of the HiCap or 140 - ?) changed the noise…? So… I think its likely to be a grounding problem. Can you change out all the SNAIC’s in that system - for known good ones - say from your 282 system…?
I can’t remember now if you said the 72 did this with the TT connected only or still did this without. If it’s just with the TT connected, what happens if you switch the L&R TT inputs. IIRC the Rega provides arm ground via the L cable (Clutching at straws here)…
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That’s the next move, albeit the other 72 has its links still in.
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I have already done a snaic 4 and 5 swap with no obvious changes. But something in that system is at fault. I’m a bit reluctant to pull my Morganas from the 282 just yet 
It makes the noise with TT connected or not. I had my TT connected when the noisy 72 was substituted in place of my 282.
I was thinking the exact same!
Start from the source and work through the system from there, making substitutions wherever possible.
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I’m hoping it’s not the rega arm on the P6. But if it is, it is.
Although it makes the noise when not connected to it.
My next move, us to swap HCs and 140s over. Leaving noisy 72 in its system to see what happens.
I’ve already sort of done that by sticking noisy 72 in place of my third system/second 72. All was quiet in that room.
Right now, it can only be HC or 140 or cables?
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You’ve just ruled out the whole TT.
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Sounds like a plan with the HC and 140. Lucky you’ve got a lot of substitute equipment to play with !
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Yes. Having a few spares should help the fault finding process. It’ll be something simple. But not it appears the new cards or the 72. Which is good, because that 72/HC/140 fed by the P6 and DV 10x5 mk2 sounds fantastic. My second listening system is often my first!
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So, an update.
Swapped my other HC and 140 into the noisy 72 system. Same noise. Even swapped about mains leads and snaics. Interesting to hear noise come and go. But that’s another story.
Then I looked at the socket I was plugging the HC and 140 into. It has a couple of usb outputs. Tried another socket and much quieter. Also, as someone asked much earlier in the thread, I do have a WiFi access point also plugged into the mains in the same room. Turned that off and my noise has gone. Yes!!!
As to why the noisy mains was only affecting the LH channel, I don’t know.
Why did it not show up with the 322 cards? Anyway…
So thanks to all that tried to help. As always these things are often simple.
However, I did learn a few things about mains leads and noise. So, this mains lead sceptic has had a bit of a lesson into of " don’t dirty up your own mains". And, how decent mains leads lower noise. That " discovery " is going to cost me.
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Because the 323’s are much higher in gain…
But - hey - you fixed it… And it was simple, in the end… 