I have done more experiments, which may help to answer questions, particularly these:
a) Can you run a normal Mini (as opposed to my oddball one) as an audio server with an SR3?_
b) Is it worth while to strip out the noisy Mini components, as I have done? (the important one raised by ted_b)
c) Is it worth going to a more powerful Mini supply if you have a good audio system?
For those who don’t want to read through the details, the answer is YES to all of these.
I was able to check a standard Mac Mini (mid 2009) with the SR3 (in the US, so the SR3 was switched to 110v, with a 2a fuse, at Paul’s suggestion). This Mini is used as a multi-purpose device, and has a lot of software to load at boot-up.
There was no problem with booting up. Although this does involve pulses to 3a, most of this time the machine wants 1.5-2a, and the SR3 was perfectly happy. iTunes with Amarra needs about 1.3a-1.4a, so the answer to a) is that an SR3 is quite capable of running a normal Mini as an audio server. It ran for several hours at a stretch doing this. However, if you want to do other things with the Mini, this might push the SR3 a bit, and you would need to watch the current demand.
We (the owners of the Minis) did some audio comparisons of the two side-by side, using both the SR3 and a Mojo Audio Joule 2, on a much better audio system than mine. The output chain from the Mini was MF V-Link, Berkeley Systems Alpha DAC, Kimber Kable balanced Kcag interconnects, Marantz MA-9S2 monoblocks, Synergystic Research X2 cables , Dunlavy V speakers (in a big room!). The entire system, including the Mini power supplies, was powered through a PS Audio Powerplant Premier regenerator.
There are four possible combinations
1) SR3 + normal Mini
2) SR3 + stripped Mini
3) Mojo + normal Mini
4) Mojo + stripped Mini
Comparisons are easier and more reliable within the pairs 1+4 and 2+3, since only the output lead to the V-Link needed to be changed; the others needed the Minis to be shut down and re-booted between comparisons.
We used 44.1 lossless rips of the following, playing directly from iTunes. These tracks were chosen because they were available, not because there is anything very special about them (but see below):
Academy of Ancient music/Richard Egarr, (David Blackadder trumpet), HMU 807461.62 Brandenburg concerto no. 2, 3rd movement
Glenn Gould 48 Preludes and Fugues, Sony SM2K 52603- remastering of original 1968-71 CBS recording, Track 6, Fugue.
P.-L. Aimard, The Art of Fugue, DG B0010765-02, Contrapunctus 1
With the Brandenburg, the most significant result was that 4) (i.e. the Mojo driving the stripped Mini) produced stunning sound, with all instruments picked out, and a real shine to the trumpet sound. 1) was good, but not really in the same league. However, when we went back to the Apple white brick as a check, the difference (negative!) was far bigger than that between any of 1) - 4). We thought the trumpet sounded like cardboard, and did not waste any more time on this comparison.
When the good power supplies were swapped, for combinations 2) and 3), the difference between the two Minis was much less obvious, but both were better than 1).
The Glenn Gould recording is old, but we thought that the Columbia engineers did a very good job. Through 1) -4) the piano sound became cleaner, more musical, and there was an increasing sense of the studio acoustic- which was a bit cramped, but apparently Gould wanted this. In this there was a definite improvement of 3) over 2)- a good power supply helps a lot!
I chose the Aimard recording since it is fairly new, and there are details about how it was recorded in the film “The Piano Tuner”. On my home system this sounds very good, but there was a surprise on this much better system. Even with 1), although the piano sound was beautiful, the acoustic seemed strangely artificial, almost as if reverberation had been added. This became more and more pronounced as we went up to 4), but here it became clear that the recording must have been made in an empty concert hall, and as well as piano sound, there is a lot of “hall” sound being recorded. Afterwards, I remembered that the film showed a concert hall being used. Here the stripped Mini + Mojo, on a really good system, is the best at showing up weakness in the recording.
Although we did not do detailed comparisons, 4) also appeared to be the best for showing up the improvement from changing from a CD rip to a 96k download.
My conclusion from all this is that there are no surprises (except on the recordings). There is a substantial gain from removing the wireless board and installing an SSD in a Mini, so long as you have a decent supply such as the SR3 (question b)), and the original point of this thread, that the SR3 gives very good audio results, is true not only for such a stripped-down Mini, but also for an unmodified one. However, if you have a good system, there is even more to gain by going to a bigger supply (question c)). As Paul says, the bigger the current capability of the power supply, the better the results. Of course, the really interesting shoot-out would be a Mojo (6a?) vs. one of Paul’s bigger units, on a really good audio rig, but it probably needs another transatlantic collaboration.
In the context of Paul’s generous “Multi-buy” offer, if you’re skint, the SR3 makes a very big difference and is highly recommended. However, if you’re not, go for the SR5 !