Starting order causes tripped fuse

Hello everyone,

I have a system that consists of the parts ND5 XS 2, DAC, 282, NAPSC, HiCap DR, 250DR.

Recently I have read about the starting orders that are recommended by Naim. It says that power amp should be started after starting power supplies, preamp and sources. But when I start my system with the order ND5 XS 2, DAC, NAPSC, HiCap DR, 250DR it causes fuse tripping at the very moment that I push the button in front of the 250DR. If I start the HiCap DR after starting the 250DR then it runs properly.

Is it possible that my system has an issue or did i get the idea wrong? Also I was wondering if it is possible to damage the system by using a wrong starting order. Thanks in advance.

While it’s best practice to follow Naim’s recommended order, I wouldn’t worry too much about starting the Hicap last. Make sure that no source is playing, turn the volume to minimum and it should be fine.

What exactly do you mean by “tripped fuse”? Do you mean the breaker in your consumer unit? If so, it’s probably a type B breaker as this is more or less universally used in UK domestic wiring, and having it changed for a type C breaker usually prevents nuisance tripping once and for all.


I start my system with the preamp muted and volume knob at the minimum, and no source playing. And it seems like everything is fine if I start the HiCap DR after the 250 DR.

Yes, I meant the breaker in my consumer unit. After reading your post, I checked out my consumer unit and confirmed that breakers are type B. I also searched for these breakers and read that type C breakers are slower than type B breakers. So I believe you think like the problem is related to peak in current if I start 250 DR after HiCap DR, and there shouldn’t be anything wrong if the breaker handles current at that peak moment, right?


I’ve actually been meaning to ask everyone else seems to have issues when turning their system on (at least that’s what I found via search) but I had my fuse box trip when turning my 250dr off is this the same thing? Would getting either a higher spec type b fuse or a type c one fitted work do you think? or should I change the order of turning things off/on?

I still follow what used to be Naim’s standard advice, in that I never turn off my equipment, with the exception of the Armageddon powering the TT and the NAT-01/NAPST, which are only powered up when in use. (I have no idea if this contributes much to my electricity bills.)

Has the advice - to leave everything switched on all the time - changed?

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I believe that your analysis of the issue is right. It is caused by inrush current of the 250.

I suspect that Naim recommend a certain turn-on order just to prevent the start-up “pops” of every downstream unit being amplified. I do not see any other reason why anything else would change if you swapped the order of the HiCap and 250.

I still leave mine on 24/7 unless there is a reason to turn them off for example the incident I’m referencing in my above comment happened when new speakers were being hooked up.

When I have my 250DR it always trip my breaker in Singapore whenever I switch it on even after waiting for some minutes and do it last.

Strangely after getting the 500DR with its separate PSU I never experienced tripping though I have only switch on like maybe 5 times so far :laughing:

My 500PS used to trip the breaker. I replaced the breaker, like for like. Problem solved. Some breakers simply go “soft”, I was told. Seems to have been my problem.

Your situation could be different. Breakers can trip for other reasons, some that pose real danger or risk of expensive damage.

Best of luck!


It does do damage. I remember my Roon Nucleus die when I trip my 250DR. I plug the Nucleus to the same WireWorld Matrix block :neutral_face:

Lesson learned.

Just to clarify B & C type ratings.
The tripping problem experienced is caused by transformer inrush current.

MCB or RCBO classification is covered in UK under BS 7671 and can be broadly categorised as follows:
Type B devices are generally suitable for domestic applications. They may also be used in light commercial applications where switching surges are low or non-existent.
Type C devices are the normal choice for commercial and industrial applications where some degree of electrical inrush is expected.

The classification of Types B and C is based on the fault current rating at which instantaneous operation occurs (typically less than 100ms) to protect against short-circuits.
It is important that equipment having high inrush currents should not cause the circuit-breaker to trip unnecessarily, and yet the device should trip in the event of a short-circuit current that could damage the circuit cables.

Type B devices are designed to trip at fault currents of 3-5 times rated current (In). For example a 10A device will trip at 30-50A.
Type C devices are designed to trip at 5-10 times In (50-100A for a 10A device).

Nothing should ever trip when you turn something off. It may be that your 250DR power switch is faulty and in turning it off, you momentarily turn it on for fractions of a second.

Anyway I would change the breaker for a type C and probably that will solve it.


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