Mains circuit

[Robbo1]

Thank you @ChrisSU for the info and advice, what differences have you noticed in the sound when using the various ‘set ups’? (i.e. using a shared ring, using a dedicated ring from main CU, and ring from a separator CU).
I’m just trying to gauge and get an idea of bang for buck.

[Robbo1]

There is a spare slot Simon, however, fuses etc are not available, it was a struggle to get one several years ago. I’m getting a nice shiny new CU in any case and all of it rearranged and tidied up.

[Simon-in-Suffolk]

@ChrisSU

Also ensure that the earth cable connects straight to the earth point near the meter, not via the main CU.
A 32 Amp breaker is usually about right. To avoid nuisance tripping when switching on Naim Classic boxes use a Type C breaker rather than the more common Type B.
Use a single 10 square mm twin & earth cable to supply the whole system. This does make it a bit more difficult to install

Depending on your setup your earth point will be your primary CU or distribution board. There will be no other ‘earth point’. If your earth is a TT system which is best for hifi (and other low mains noise) applications in my opinion, this will likely be the case if compliant with regs so I understand, and is what I had installed.
Also a ring is nearly always preferable to a radial where multiple device sockets are installed, so 6.5mm T+E in a ring will be preferable to a single 10 mm T+E on a radial for lower impedance and reduced voltage drop.

I think it’s probably best to let your electrician design the installation… they key thing should tell them is the current and the maximum voltage drop you want for the ring or for single device radial and how many sockets you want installed. A 6mm radial in enclosed ducting can not exceed 32 Amp breaker… for a hifi circuit I would be looking for 16 or 20 Amps (or possibly less) with a timed trip (slow trip)… again your electrician can suitably design, but you should stipulate, as you say, the slow trip, especially if you have large power supplies or power amps with large transformers.

6 mm T+E on a radial is 7.3mV / Amp / metre
10 mm T+E on a radial is 4.4mV / Amp / metre
6 mm T+E on a ring is 3.7mV / Amp / metre
10 mm T+E on a ring is 2.2mV / Amp / metre

However 10 mm T+E is a bulky cable and is typically used for long electric cooker and shower radials. 6mm T+E is still quite a bulky cable and is typically used for shorter cooker and shower radials.

So you can see the length of the ring or radial to the CU becomes an important determiner for the cable type. This will vary from installation to installation.