XPS DR Circuit Breaker issue?

Exactly. You want to be able to turn it off when you go away and to know that you can turn it on when you get home without encountering any problems. A type C breaker should fix it once and for all.

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This is a design flaw in my opinion. They should have some kind of current limiting circuit on startup. You’re not supposed to blow your own fuses! This is hard on the transformer windings too. I know a lot of the higher power amplifiers do this. It doesn’t take much extra circuitry, so cost shouldn’t be an issue. These power supplies are ridiculously overpriced anyway.


Exacly what I’ve said if you scroll up … However, on this Naim forum almost every member seems to accept these things because of ‘sound quality’ … there are more appliances which draw quite an inrush current, it’s not rocket science …


Perhaps many people who post here aren’t concerned about the power-on issue, as tripping their fuseboard/whatever is a pretty rare event and if this does happen it could be an indicator of other issues with a property’s wiring(?).

And the guidance is to leave the larger PSs switched on 24/7 - IME they can take a week or so to warm-up.

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They can’t be that flawed or overpriced if you’ve bought one.


I’m sure the answer you will get is that, yes it is true and yes Naim have tried this but in the end like many other things it impacted too much the sound quality

It doesn’t take faulty wiring to trip an MCB, it’s simply that the unusually large transformers Naim use draw a large inrush current very briefly when switched on, and a standard Type B breaker is not designed to cope with it. A dedicated circuit with a Type C breaker is the correct solution. For example, my NAP200 would nearly always take 2 or 2 attempts to power on without tripping a Type B breaker. After fitting a Type C it never happened again.

The XPS is not the only box to be susceptible to this. I think there is some confusion here with its habit if blowing its internal fuse when switched on, which the OP has not experienced.

What is strange is that you mostly hear about tripping circuit breakers associated with the XPS and XPSDR. I don’t remember reading of such problems with any other Naim power supply, even the CD555PS which must draw as much, if not more, current than the XPS at switch on, although I accept there might be such cases.

So it appears to be a circuit design that is unique to the XPS that is causing this problem. I suspect Naim must know what it is about the XPS’s design that causes this circuit breaker tripping behaviour but they have chosen to leave it be, presumably for SQ reasons.

I don’t think that’s right. As I mentioned above, it’s the internal fuse blowing that the XPS is particularly prone to, as often mentioned in forum posts, not tripping MCBs which other boxes can do too.

Fair comment, but it still must be something about the XPS’s design that causes its fuse to blow more readily than other Naim power supplies, unless the XPS has a down rated internal fuse for some reason.

Turning on the NAP used to trip the breaker every now and then at one place I lived. Turned out the mains wiring was very old. Getting it sorted also sorted out the breaker trips.

Regarding the equipment fuse in the XPS, yes it is more marginal. Richard mentioned it many times and it’s also in the fuse FAQ. IIRC, the next higher available fuse value would be unsafe, and changing the XPS to draw less power when switched on was considered to impact SQ.

That said, the only time the fuse blew on my XPS, while I owned it, was when the power cable was plugged in shoddily.

The 555PS and 300PS have higher fuse ratings, so are less likely to blow it

As for the circuit breaker, I have a B on a 16 amp circuit, and sometimes it triggers, usually it’s when powering on the 300PS. (More rarely the 555, I think, and never the SC). But it’s maybe one out of ten times, so it doesn’t bother me at all. (I don’t have the XPS anymore, so can’t say if it does it)

Well that explains it nicely. Looks like XPS owners just have to have some back up internal fuses and possibly change their type B circuit breakers for type C.

I had an XPS for several years and it never blew a fuse. Mind you it was on 24/7 except for holidays, storms and the like.


Yes, the only time my XPS blew the internal fuse, it was my own fault for not plugging the power cable properly. (When I touched it, it arced and blew the fuse).

And same as you here with the B circuit breaker, one out of ten times (or whatever it is) means maybe once a year in practice, because I usually leave it on, so I flip the switch on the breaker and don’t care.

In the days before we all moved towards LED light bulbs, did no one wonder why their house lighting circuit MCB would invariably trip when an incandescent light bulb “blew”? High current caused by the bulb’s filament going open-circuit tripping the MCB.

The same is effectively happening here with the transformer’s inrush on larger linear power supplies pushing the tripping curve of a Type B MCB to its limit.

Have had customer’s suffer the same fate with larger NAPs, SuperCaps, XPSs, etc. and all instances have been resolved with fitting Type C MCBs instead of Type B.

Internal fuses blowing on XPS-2 & XPS-DR is a completely different matter. The fuse rating is designed to protect the product under fault conditions, but is specified quite close to the fuse’s upper limit I have previously been told by Naim tech support. Invariably these blow due to the fuse’s filament being weakened after the PS has been repeatedly switched on & off (a bit like that of a light bulb failing!!!).

Hope this helps.


I had that same issue with my xps blow fuses triping the fuseboard it has a high current draw, but the fuse is doing it’s job but i have 555ps now and no fuse blown yet strange.

Imagine if Sony produced a TV that blew its fuse occasionally when turned on. You’d have 10 million calls to technical support a week. And imagine if Sony’s response to the call was to leave your TV on all the time. :joy: Or call an electrician to come and change your breaker. :rofl: I’d imagine most of those TVs would get retuned as being faulty.

Why is it that this can be considered acceptable in the hifi industry? Come on Naim. Get your act together. This is unacceptable engineering. The solution isn’t going to affect sound quality. Other manufacturers deal with it. What a lame excuse.


Sony are not Naim. They also don’t use Burndies that need massaging, dedicated equipment stands, separate boxes for power supplies, Snaics that need shaking, elaborate decoupled cables, etc.
If you really believe all this stuff is just some sort of unacceptable hocus pocus engineering you don’t have to buy it.

TVs don’t have or need high capacity power supplies with large transformers. And as I mentioned in a previous post, the high inrush current is not unique to Naim, and there is an easy, cheap (around £4 last time I looked) solution that doesn’t need an electrician to fit if someone knows what they are doing*, which is to replace the type B MCB with a type C, which is made specifically to enable electricity supplies to provide the high startup current drawn by some equipment, recognising a need. This does not suggest the design of amps or their power supplies is unacceptable just because they have a high inrush current.

*And if not should cost next to nothing for an electrician to do as it’s a less than 5 minute job.

Of course, it may be, indeed I think very likely will be, that before too many years pass more electrically efficient power supplies (e.g. SMPSs) will replace the linear ones causing this issue.

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