Can an SR3 also run a mid-2010 or later Mini?

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boblloyd

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Can an SR3 also run a mid-2010 or later Mini?
« on: 21 Oct 2013, 06:37 pm »
This is a genuine question: has anybody tried this yet? Alternatively, has anybody measured the actual current draw from a power supply into one of these, under music conditions? I showed that all was fine with the earlier Mini and an SR3-15:
http://www.audiocircle.com/index.php?topic=108737.0

and it still is fine, but what about a newer "unibody" Mini, with the reduced 12v dc power supply?

A detailed report from
http://www.anandtech.com/show/3843/apple-mac-mini-review-mid-2010/7

suggests that the average ac power demand for the 2010 Mini is 15w when web browsing, a similar demand to iTunes on my machine. Given Apple’s efficiency figure of 85%, this translates to just over 1a for the output of a 12vdc supply, so a 12v SR3 will work for this perfectly well. What about an SR3-15 like mine? Paul suggests that taking the 15v unit down to 12v loses about 40% on maximum current draw, so 1.2a would be the new limit.

Clearly, it’s a killer for my SR3-15 if you have to work with the output trimmed down- it would be running far too close to the current limit.

But do you need to reduce the o/p voltage at all from 15v? This may seem a bit heretical, but it’s worth remembering that in the early days everybody said (and some still do) that you MUST have 18.5v for one of the earlier Minis. In fact I have used anything down to 12.6v, and there are reports that 10v would be OK.

 Apple have now changed to a 12v supply, but have they changed much else inside for the internal voltage controllers which step down to the various voltages needed by the circuitry? There is one bit of evidence which suggests not. The other people who are keen on external dc supplies are those who mount Minis in cars. On the MP3Car site, if you search for

How to Power Your 2010 Mac Mini In A Vehicle, by MCT

you can find  a report that they ran a 2010 Mini at everything up to 15v; the only comment was that regulators are recommended(!)
Thus I don’t think it’s too fanciful to think that my supply, unmodified, would drive at least a 2010 Mini, and probably anything later as well, but it would be an expensive mistake if I'm wrong......

Any comments would be very welcome!