Naim transformers ratings (for balanced transformer sizing)

Hi all,

Do you know where it is possible to find the transformer ratings of different Naim boxes? I am asking because I am currently using an Airlink Balanced Transformer (EUCBS2000, rated at 2000VA) to deal with the SN2 buzzing, so I want to ensure that it is not limiting my system in any way. Also, what is the recommendation for the balanced transformer size in terms of overhead for such applications?

My system is as follows:
ND5XS2 (?? VA)
nDAC (?? VA)
SN2 (400? VA)
HiCap DR (450? VA)

I suspect the source transformers aren’t as large as the amp ones, but better to have a definite answer!


Surely the transformer in each is not the detail you need, but the maximum power draw of the complete unit - which I think is published in the specs?

Ideally a balanced PSU is rated for the circuit to give the full current headroom. Which is what they do in hospitals. So a 20A circuit would use a 20A transformer.

Which would be a large unit located by the consumer unit, not sitting in the rack.

I think the 2nd question is probably much more relevant & useful…

But… YMMV…

It’s a 16A circuit in my case, which I suppose translates roughly to 3800VA for 240V. At least that gives a sense of the maximum applicable size.

@Richard.Dane balanced transformer supplies have been discussed before for removing DC offset etc. Isn’t HiFi corner the most relevant category?

I think most mains related topics are best in the Lounge as it’s not strictly Hifi and often requires moderation or sometimes even removal. The forum is international in its membership and with all things electrical, what applies to one territory rarely applies to the next, so any advice given could easily be read and misapplied with potentially fatal consequences.

I thought about that, but I am afraid such info is not available. Best I could find or calculate:

Power Consumption

  • ND5XS2: Typical use: 11W
  • nDAC: <30VA (max. inc iPod charging)
  • SN2: Power Consumption (quiescent) 10VA (on the website), 37VA (on the manual), power output: 2 x 80W @ 8 Ohm, 2 x 135W @ 4 Ohm
  • HiCap DR: max output 2 x 24V x 0.3 A = 14.4W. Consumption should be higher due to losses.

So worst case scenario would be something like 330W/VA?
As a matter of fact, I have measured the system consumption via a smart plug and the maximum I could see was at the order of ~30-35W IIRC. So probably I am overthinking this (but that’s what engineers are for :innocent:).

Fair enough!

With intensive music on at the loudest you or anyone in your home will play it?

One thing possibly to consider is handling of brief peak power demand - i’m thinking in terms of switch on surge. Inhibiting the supply during that period shouldn’t be a problem, but need to be sure the transformer won’t be damaged by such a surge. I doubt your smart plug gives you a reading fot peak current?

If you don’t simply want to go with minimum 16A rating, you’d do best to contact Naim direct to check power demand. But if you go for anything less than the breaker rating, the transformer potentially could be at risk - and possibly a fire risk - if anyone were to inadvertently plug in something with very high power draw, e.g. 3kW, unless it has inbuilt safe overload protection*. In that situation suitable precautions would gave to be put in place (possibly permanent and clear marking with the maximum power rating on all connected sockets, which for each socket would need to be the transformer rating divided by the number of sockets). If the transformer has safe overload

*But if such protection shuts down then it might be tripped by switch-on surges…

On balance going for 16A - in practical terms 4kW - would seem best.

Just to add here, that for anybody looking for mains electrical related advice, you should always ask a qualified electrician who is fully conversant with the electrical code for your region.

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According to the published specs, the following apply:

Property Value
VA 2000
Input Voltage 230
Input Current 8.6
Output Voltage 230
Output Current 8.6
Output Termination Two Schuko 3pin sockets
Weight 13kg
Primary Protection Push to reset circuit breaker SP8
Surge Protection SL32 Surge Limiter
Product Type Safety Isolating transformer Conforms to EN61558-2-23 CE & RoHS

I assume the protection is consistent with its 8.3A current rating. It has never tripped on power on. Indeed the smart plug doesn’t capture any peak currents, it provides an average reading per 30-60 sec I think.

Regarding the hum blocking, the SN2 is quieter when plugged in the balanced power supply. But a faint buzz remains nevertheless… The balanced transformer itself is buzzing on startup and when the hairdryer is on, but is silent otherwise. At least it does seem to block a bit of dirty mains downstream…

As for getting a bigger unit… One day, if I ever move house, I’ll do the full treatment with separate CU, thick cable and so on. Until then, my hands are tied!

That suggests it is failsafe if overloaded, so if it were mine I wouldn’t worry about it at all. other than possibly with switch on surge (the magnitude of which is not known to me, there is no way your system will exceed, or get anywhere near, 8A at mains voltage, roughly 2kW.

On this basis, if the transformer’s cutout doesn’t trip in use, I’d question the benefit of changing the transformer for a larger one unless you can hear first that it makes a significant difference in sound, or someone whose neutrality and hearing you trust, using a similar system with similar hum issues, describes a benefit you feel is worthwhile.

But as Richard indicates, to be definitive on safety you should consult a qualified electrician, but checking first that they have direct knowledge and experience of isolating/balanced transformers as I doubt mist have.

This is direct from Airlink’s own installation notes:

“For best results a dedicated spur circuit is recommended. This will avoid many problems with mains pollution caused by various equipment –hair dryers are a typical source.”

Unfortunately that looks misguided advice. Radials will not remove mains ‘pollution’ compared to rings assuming all our ganged together via their circuit breakers at the consumer box, though they could slightly reduce it.
Some cheaper and older designed hair dryers ( and many other things) can cause asymmetric loading when on half or reduced power and that can introduce a small amount of ‘DC’ on the mains.

For best results for noise reduction, and this is often done in recording studios and the like, is to switch to a TT utility earthing system. I have done that however not initially for hifi , but boy with my Naim equipment it made a real worthwhile improvement as a happy side effect. I use rings and spurs in my house, with a couple of radials for very high load devices.

Naim recommended to me that a separate consumer unit taken direct from the meter was an important part of a dedicated mains circuit. Having tried with and without, I found an otherwise dedicated circuit taken from a spare way on the main house consumer unit to be of little or no benefit. Taken from a separate small consumer unit, the benefits were quite noticeable.

This is adding a small amount of source impedance… likely mostly resistance… I minimum impact on HF/ RF voltages or ‘interference’, but should help on the lower frequency effects of inductive in rush loading dips and perhaps the effects of saturating transformers.

I remember several years back with some specialist scanning equipment tracing RFI caused by mains in a house along about .5 mile of over head wiring leading to that house… it was very revealing…

Thank you for confirming that the use of the transformer is safe in principle.

In terms of sound quality, thankfully I can borrow my partner’s ears which are very discerning in identifying differences. I haven’t got around to do an A-B comparison yet, and it might not be that straightforward given that I have to shut down everything and power it up again. For now I want to keep it in place for some long-term listening and get a baseline for the “feeling” that I get from the system.

I will get to a direct comparison though one of these days!

Thankfully (?) TT earthing is the standard here in Brussels. Of course, the earth is shared with the rest of the building. We are going to have some electricity works on the common installation soon, so I am planning to ask the electrician to improve the earth impedance as much as possible (not just below the legal requirements, but even lower if we can sneak in a rod or two :wink: :innocent:.

Improving the earth conductivity can result in new or larger ground electrodes, multiple Earth points, and larger gauge Earth wiring. In the UK there are earthing conductivity tests that have to be met for TT installations. Be interesting to see what they do if it’s a shared Earth system… you might want your own separate earthing system… certainly if you own the land where the electrodes will be inserted into.

The (old) building is a block of 5 apartments, 1 per floor. So I suppose I am a co-owner of the land legally. There is a requirement of < 30 Ohm earth resistivity for conformed installations. I believe ours was measured 10 years ago at 10 Ohm, but we will see what is the current situation and if any additional rods will be needed.

The earth is common for all apartments, with several rods going in the ground via the basement. All metal pipes (heating, water, gas etc.) have to be connected with equipotential bonds, so not so sure if it would be possible to have my separate earth. Doesn’t hurt to ask the electrician though!