Dual power supplies - a question

Naim nds.
Dual 555ps power supplies.
One for analogue, one for digital.

Can you switch one power supply on before the other?
Will this cause any damage.

If not, does it matter which supply is connected before the other?

Reason for question:
The 555ps power supplies are connected to a mains regenerator.
Switching BOTH supplies on at the same time produces a current surge which the regenerator does not like.
It would be good if I could switch on one supply, wait a minute, then switch on the other supply.

Thank you, in advance, for your help.

No, I gave not contacted naim yet, I will only bother them if no-one has experience of this.

The ND555 seems to have a power button and surely you have the unit off when you turn on the PSes? Then why would it matter?

As for the PSes themselves, if you turn them on by using their power button (as you should), it is virtually impossible to turn them on at the exact same time, anyway. So whether there is 0.5 secs, 5 secs or a minute between PS1 and PS2 doesn’t really matter

I’m sure it will be fine. They are powering different bits. If it were me, I’d switch the digital on first, and then the analogue. I’ve no idea why, but it just seems logical.

Comically, I do it the other way round, thinking that the analogue circuits couldn’t give two hoots whether or not the digital circuits are powered, whereas the digital circuits might be “upset” if they “find” former are not…

My thinking is that the analogue might get confused without the digital, as it’s the digital that tells the analogue what to do.

Did you ever have two supplies on an NDS? From memory I don’t think so.

I never had an NDS (preferred the CD555, although I never heard an NDS with two power supplies), but have had two from the beginning on my ND555. At which point I have to admit the NDS bit rather escaped my eagle eyes, but I suppose they may well behave the same.

I would expect the analogue circuits to quite simply be either on or off and not check for or expect anything at all (whereas the digital circuits may do so), but my understanding of these things is exquisitely limited…

Yes, we are both guessing! I’m pretty sure that the proper answer is ‘it makes no difference. Let’s check with Naim… hello @Stevesky ….

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I have an nds, not an nd555, however, these streamers do NOT have a power supply button.
Otherwise, I would follow your suggestion.

Everyone else
Thank you for your comments, they are very much along the same lines as I have been thinking, but I have not had the courage to try them out.

It would be great if I could get an official view from Naim themselves on this forum.

If so, a big thank you in advance.
No rush.

Interesting, the ND555 picture on the Naim product page does show a power button, I had looked it up. Maybe they mixed up the pictures again and it’s an NDX2 :smiley:

In this case, I suppose the manual would say if there was anything special to observe

Yes, ndx2 does have a switch.

Nothing in the manual about dual power supplies.

Thank you though.

You’ve done the same thing I did! The OP has an NDS not an ND555 :slight_smile:

I’d email or call their technical support. Then please let us know what they say :slight_smile:

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Great minds … :wink:
Yes, I know that now about the NDS, but I didn’t know when I wrote my first answer about the power button, because he hadn’t said what he has and there is nothing in the profile :slight_smile:
[Edit: It’s in the very first line. I overlooked it, sorry]
(And I thought if the ND555 has one, most likely an NDS would too. Bad assumption …)

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Thank you for your help.

Of no consequence, but I did say I had an nds in the very first line of my request for help.

I will email naim on Monday.

However, if anyone has experience of using two 555ps power supplies with any naim device, AND
they have NOT switched them both on at the same time.

Please tell us

Which supply was switched on first, and more importantly from my point of view

Thank you

I have 2 non-naim power supplies on my NDS and it doesn’t seem to make any difference which order I switch them on in.
The NDS happily boots up either way.

I did spot it was an NDS but made the wild assumption that the ND555 would operate similarly. This based on, again a possibly wild assumption, that Naim would make it absolutely explicitly clear if switching on in a ‘wrong’ order was likely to damage either unit.

But what do I know…



(and, to be fair, just about everyone else)

Thank you.

This gives me considerable confidence that

Sometime next week, I will try this and report back.

@Darkebear may surely help here. He had dual ps on CD555 then Nd555.

I did not know if it was safe or not having one part powered before the other or not - assumed a staggered-start powering would be OK with about 1-2 secs between ‘on’ whichever supply went first.

This worked fine for both CD555 and ND555 for the many years I have had the former and now the latter.

In short - just turn one on, wait a count of about two seconds and then turn on the other and it will all be fine. :slightly_smiling_face:

Most designs allow some time for things to become stable with muting relays and the like, which is usually several seconds, so do your on-sequence within that and it will all work fine.


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