The system switch on and off orders are:
Power ON:
Sources
Power supplies/Pre Amp
Power Amp
Power OFF:
Power Amp
Power supplies/Pre Amp
Sources
My Naim DAC is plugged in directly to the wall to power its digital circuits and also to the 555DR to power its analog circuits.
Should I switch on the DAC first and then the 555DR?
I always turn my power supply on before the nDAC.
Hi Nathan
Thanks for letting me know that.
Do you have a reason why you do that?
Thanks
Jim
In that way the nDAC is only switched on when it has both digital and analogue power supplies available.
Although I’ve not thought about it more deeply I’ve never had any problems doing this.
Whereas I do exactly the opposite: turn on the rack - including nDAC - before turning on its XPS.
Thanks Both
I looked at the nDAC manual yesterday, but got distracted by work before I found it.
When I get time from childcare (i.e. never) I’ll have another look unless someone who is sure comes on a let’s us know either way.
Got the user manual open at the moment.
Can’t find any mention of switch on order, only that the unit does mute during start up.
I am assuming that the XPS/555 powers only the analogue stages…
To save you time, the manual doesn’t mention it. If it were me, I’d turn on the 555 first, for exactly the reason mentioned by Nathan. But given that suzywong does it the other way and lives to tell the tale, it clearly doesn’t matter.
The whole reason for the power amp on last and off first is to stop bangs over the speakers, so how you turn on sources is far less of an issue.
From the DAC White Paper
When the PSU upgrade option is used with the Naim DAC, power supply separation is further increased by the use of a dedicated supply for the master clock circuits. It also provides a bigger toroidal transformer and bigger reservoir capacitors, and the DSP remains powered from the Naim DAC transformer to give even more separation from the analogue section
Good info, I hadn’t thought to look at the white paper. I don’t know whether the nDAC uses the WM8804 IC, but that particular chip prefers the back half powered up before the front half receives the bitstream; in practice though, the chip powers up and stabilises long before the upstream processor finishes booting and activates the bitstream.
From a previous life, I recall that we turn spacecraft on “front to back” so that the each stage’s signal stabilises before the next stage goes live. It also avoids floating inputs to a stage.
Indeed. Incorrect sequencing here can get very expensive, very quickly 
T’weren’t me wot done it, Yer Honour!
The nDAC goes into a start up routine when you switch it on, and various lights flash on the front panel as it looks for a source and identifies whether the signal is hidef or not.
If you switch on the psu before this process has begun, does it start the analog sections of the nDAC before the nDAC control circuits are on?
If the XPS powers only the analogue circuits, then there will be no “boot up” time like with a digital circuit. For sure there is an “inrush time” when the input caps all charge up, but this is the order of a couple of tens of milliseconds max - we always get our suppliers to measure it; I had a case many years ago where the suppliers pSpice analysis of a particular unit reckoned 0.5 Amps inrush current - the reality was 6 Amps, and I was attempting to power up six at a time…needless to say, the Central PSU tripped out every time…… oops!
I “forgave” the circuit designer coz he was a staunch Nightwish fan!
Ok, so if I just switch on my psu and that wakes up the analog circuits.
Then turn the nDAC on and it can attend to the DSP and digital parts that it powers, and not have to reset things later when an external psu is added.
Is that best, or do you still prefer to do it front to back, and let it reorganise itself electrically when you switch on the external psu?
Personally, I always power up front to back……with all my multibox systems (Linn Aktiv Briks, Naim active SBLs and Meridian DSP5000).
Power off in reverse order.
But then I am probably overcautious - by training……
And do you add milk before or after removing the teabag?
ROFL…not a tea drinker
And I don’t use the inversion method with my Aeropress nor do I measure my ground coffee or water to the nearest gram!
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