Unitiserve power supply/mains cable missing

The US SMPS supply is a standard item, mine supplied with US-SSD last year is an ENG model 3A-505DB12.

The effects of substituting another supply will vary depending on where you have your US installed and how you use it, and how good your mains is. Many factors at play.....

A specific characteristic of this supply is that DC negative output is connected back to mains ground, which keeps the US chassis (and Ethernet/SPDIF) shields grounded.  The US as a computer does radiate EMI, hence Naim recommend physical separation. Naim's "negative=ground" design choice may help reduce induced noise into partnering equipment, eg through cable shields. While breaking this with a different PSU may not stop it working, it may have other un-intended side effects on the overall musicality of your system.

 There should be equivalent products to the ENG model in the market, I gather Naim has used different vendors over time.  Once I found a list of equivalent part numbers on Google.

Its good that you have the power cord with the filter bump - this makes quite a difference to the overall mains quality and I wouldn't use without.  Naim go to the trouble of ensuring the filter acts on phase/neutral only and bypasses ground to preserve the direct ground path, its more sophisticated and specific than a clip- on ferrite.

The popular Israeli after-market "linear" supply really contains an SMPS followed by a regulator. It doesn't appear to follow the same negative=ground principle, or any internal mains noise suppression -  only use with the Naim power cord.  IMO it has swings & roundabouts on the benefits it brings - it too has compromises that only a truly-linear grounded supply can overcome.

Thanks 40 below,

Reply from NAIM, thanks for their quick reply, is that the AC adapter is readily available from NAIM dealers and is around £50 plus VAT.

Might help someone else who looses that second part of the mains lead.

Thanks

Dan

Glad yo have a replacement in delivery. You received audio quality advice on choosing your supply. 

As as a technical aside, however, you asked about compatibility given voltage (12 V) and current (4.7 A) specs on the US. The voltage is the one to match properly - a 6 V or 18 V supply won't be nice for a circuit designed to operate at 12 V, that's for sure. The current is more of a minimum requirement, though, not something to match exactly. The US draws whatever current it needs from the 12 V supply, and the spec tells you it won't need more than 4.7 A. A new supply that indicates it can source 5 A meets this requirem and is good to go, as would a beefier 12 V unit that could deliver 10 A or whatever, but you shouldn't use a smaller unit, say that could only supply 2 A, since it will over heat or deliver a lower voltage (or both) and may damage itself or your US. 

Short answer: replacement PSU should have exactly matching voltage and at least as much current as it specifies on your US. So you could use the one you have while awaiting delivery of your Naim branded replacement as long as the connections all fit and have the same polarity. 

Regards alan 

Dear alan33,

Thank you that is well explained and makes total sense, I am ordering the NAIM supply and while that is travelling I will use this spare one that just happens to be a fit for the connection and the amps/voltage.

Best

Dan

Used spare 5a 12v AC adapter and it is all working fine. On for three hours while the library re-builds and no issues so far.

Just in case a future search brings this up it has worked ok, but still ordering the NAIM AC adapter later this week.