[boblloyd]

Anybody reading this probably knows that the SR7 from Paul is very highly regarded as a supply for audio with a Mini- see comments from Serengetiplains on other pages, for example. However using the SR7 does double the cost of the computer, or treble it, if like me you picked up an older Mini (mid 2009, 4G) on eBay.  Do you have to have all this power, or is there a cheaper alternative?

Somewhere Paul comments that the audio demands alone are likely to be much less than Apple's quoted 85w max. for the Mini. This is even more likely if you follow the Item Audio route of removing noisy bits like the HDD (replace with SSD) and rip out the Wi-Fi and Bluetooth board and antennas. I did that with a mid-2009 Mini, and preliminary mesurements with a cheapo 15v linear supply (see below) suggested that an SR3 would be perfectly capable of running my machine. I ordered an SR3-15 from Paul, to include the iSense resistor;  it has arrived, and here are some results.

On power-up, not surprisingly, the current jumps all over the place,  most of the time between 1a and 1.5a, though there are a couple of pulses to 2.0-2.1a, and then it settles to  0.5a-0.6a. Starting up Temperature Monitor, and Audirvana/iTunes, again gives very variable numbers, but mostly only up to 1.5a. After startup, running both of these  consumes about 1.0a to 1.1a.

The mini is headless, so I access it remotely over my home network, with an Ethernet bridge from an Airport Express. This remote access while running pushes the current up to 1.5a-1.6a, but I don't need to do this very often. In summary, I have an audio server running with only half the rated current of the SR3 most of the time- pretty much what I hoped for. The SR3 case scarcely gets up to blood temperature, so it is very happy, and it has plenty in reserve.

Other Minis might behave differently, so if anybody else wants to try this route, I would recommend a preliminary check first, to find out what current your Mini wants, especially if you use more than just audio. You can of course use the standard Mac white brick supply for this, but you do need to break into the cable to measure current. This takes some nerve, but it's perfectly OK. If you don't fancy this, you can use a different supply, and you can get a perfectly useable cable with the Mini plug from Carnetix- it does not have a shield connection, but I am running the Mini floating, and it is perfectly happy.

Item Audio do a very cheap 4A linear supply to go with  their stripped-down Mini, and I did my first tests with this. It's made by Rapid Electronics, and you can get it even cheaper elsewhere. Mine is now surplus to requirements- any offers?

So what does it sound like?

For me, it's a revelation; the change is far more than I expected. I have been working up slowly with computer music, and every improvement I made did something, but did not come up to  my reference of CD, using a Linn Ikemi as transport, feeding an Audiolab MDAC. I thought this gave excellent sound. After the strip-out, and the replacement of the brick by the Rapid supply, the  Mini sound (with MDAC) was approaching the Ikemi in quality, but I still preferred the 'presence' of the Linn.

Not any more! I have done direct A/B comparisons of CD vs the rip on the Mini for various CDs (very easy on the multiple source MDAC). Several curtains have been pulled back, and the definition, both in sound and instrument position, is far better than anything I have heard from the system. The 'presence' of the Ikemi now seems a bit artificial- I guess I have been listening to "Linn sound", but what I now have is the music, and it feels as if there's nothing in the way. I suspect I'm now limited by my system. If you have a really high-end system you might get even better results with one of Paul's bigger supplies, but unless I improve my components (Audiovector 3X , Transparent speaker cable, Flying Mole Class D MAS160 amp, Creek passive taking the MDAC output, Mark Grant interconnections) I am more than happy with the SR3, and there's still high resolution to come.

[ted_b]

Bob,
Nice review.  I have the SR7-18V5 powering my mid-2009 Mini, and love it (I occasionally dial it down to 12V and run my Auraliti PK90USB Linux server off it instead).  How tough is it to go in and rip out the Wifi and bluetooth board(s)?  Is it worth it?

[boblloyd]

Thanks, Ted.

Cutting the white cable to the brick takes some nerve, because it seems so irreversible (it's not; a 3-connector XLR with shield, M and F pair, will repair the damage, and also allow easy swaps of power supplies to the Mini, and, if you want, breakouts to measure current).

Opening up the case of the Mini for the first time takes even more nerve- even with the very good instructions on several web sites, it's terrifying. There are loud popping noises, but the procedure does work, and the second time is a doddle. The critical thing is to have a putty knife (two are better) which is as thin as possible. I found something called a "chisel edge" paint scraper (B&Q if you're in the UK) which is even better, because it's both thin, and tapers at the front edge. Once the case is open, HDD swaps and removal of the wi-fi board are both relatively trivial- again there are instruction sets, with good pictures, available.

Was it worth it? Difficult to say, because these were the first things I tried, separately, still using the noisy white brick. Each of them did appear to produce a small improvement, but if the noise from the brick was dominating, which is likely, then it would be small, wouldn't it? I went that way because a) I was too mean to buy an Item Audio modification, and b) I wasn't totally convinced that I would hear the difference. I am now! They also do other things which I'm less sure about, and are more difficult.

The critical experiment would be for somebody with  a really good power supply (now who might that be?) to try these changes on an unmodified Mini.

[boblloyd]

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 !

[Alan UK]

Thanks for sharing your experiences Bob, they make for interesting reading. I appreciate your methodical and thorough approach, which is good as I'm sure many people want to make the same comparison. Food for thought...

[Alan UK]

My stripped down Mini is now in a similar place to Bob's. Following the advice of Mark, of ItemAudio, this is what has been done:

Small SSD
SOtM SATA filter
Optical drive removed
All Wireless/Bluetooth antennae removed
Bluetooth board removed
Fan removed
Large heat-sink with fins mounted to CPU (Mini now recased)
(GPU has standard heatsink only, Mini is used headlessly)

According to the readout on my Belkin PF40 the Mini draws almost no current. So far, using a VNC programme and SMC fan controller, the operating temp hovers around 33C. If I connect the monitor and mouse to research something on the web for a while, the temp sticks at 42C. I'm pretty happy with these results.

I am even happier that each modification (I did it in stages) has bought about very recognisable changes, with a most definite cumulative improvement (There was one stage where I thought I had a retrograde step, but some experimentation and the completion of the next stage showed it did add to the overall improvements). Given the above I have made arrangements to buy Bob's SR3, once Paul makes Bob's SR5. Having laid the groundwork, I am excited to see what the SR3 brings to the system.

Thank you Bob, and Paul, for introducing a new and productive train of thought that has improved my system significantly.

[boblloyd]

Congratulations, Alan!

In fact I would say your Mini is probably now well ahead of mine. I've no doubt the SR3 will improve things even more (but I would say that, wouldn't I?). I'm impressed with your doing this by stages- I still find opening up the Mini a bit scary.

The biggest change to me looks like the re-housing of the guts of the Mini. Any chance of some pictures of the new rig?

[Alan UK]

Hi Bob, Thanks for the kind words.

Opening up the mini isn't hard when you've done it so many times - The iFixit site has an excellent step by step tutorial that I relied on heavily.

The case in question is one of these Mini ITX cases, for about £30 on Amazon: :

As for a picture, I would be embarrassed! Maybe in a few months, after I get around to tidying it up... not very high priority, as it lives in a cupboard! I took the easy way out when it came to re casing - I left the logic board attached to the standard Apple baseplate, along with the backplate and its incumbent sockets/switches. I simply mounted it (basically the bottom half of the complete mini, with cooling fins sticking out the top) at the rear of the ITX case and secured it, using the open back of the ITX case to access the rear of the mini.

The SSD and SATA filter are mounted on the 'top tier' within the new case, utilising existing screw holes (you can always drill more at your convenience and stuff wherever you want). The SATA data/power cable back to the logic board is 30cm long.

I haven't bothered connecting any of the ITX case's plugs, sockets, switches or lights. Because I am lazy. Also, to be honest, the whole thing is a proof of concept exercise for me; I plan a proper audio computer build in a year or two, probably following the ItemAudio 'recipe' for a T1 transport.

At that time, I will likely return the Mini to stock either for home use of for sale.

[kenreau]

My stripped down Mini is now in a similar place to Bob's. Following the advice of Mark, of ItemAudio, this is what has been done:

Small SSD
SOtM SATA filter
Optical drive removed
All Wireless/Bluetooth antennae removed
Bluetooth board removed
Fan removed
Large heat-sink with fins mounted to CPU (Mini now recased)
(GPU has standard heatsink only, Mini is used headlessly)

According to the readout on my Belkin PF40 the Mini draws almost no current. So far, using a VNC programme and SMC fan controller, the operating temp hovers around 33C. If I connect the monitor and mouse to research something on the web for a while, the temp sticks at 42C. I'm pretty happy with these results.

I am even happier that each modification (I did it in stages) has bought about very recognisable changes, with a most definite cumulative improvement (There was one stage where I thought I had a retrograde step, but some experimentation and the completion of the next stage showed it did add to the overall improvements). Given the above I have made arrangements to buy Bob's SR3, once Paul makes Bob's SR5. Having laid the groundwork, I am excited to see what the SR3 brings to the system.

Thank you Bob, and Paul, for introducing a new and productive train of thought that has improved my system significantly.

Hi Alan, Bob, Paul, et al

Great reading your reports on optimizing all the latent potential in a mac mini.  I have a 2010 mac mini that has the Mach2Music OSX minimization, SSD, 8 GB Ram and a PI Audio power cord.  After reading all the positive reviews of the SR upgraded power supplies, I'm am looking into those further and possibly following your lead in transporting the internals to another case to simplify some of the implementation for the 2010 aluminum unibody case.

I need to ask how you operate and control the mac mini if all the wifi and bluetooth boards are removed?  Is it just simply by a usb key board plugged in and a monitor/display?

I have my mac mini set up in a cabinet and I run it headless from an iPad and apple bluetooth wireless keyboard.  I imagine then I would need to keep my bluetooth board, but could possibly pull the wifi board if that is worthwhile(?)  (I have an ethernet cable connected).  Did you have to pull the optical drive to make a place for the SOtM SATA filter?


Thanks
Kenreau

[boblloyd]

Hi Kenreau,

This raises an interesting set of new questions!

To deal first with your own question, I do my headless and wirelessboardless control in the way Item Audio recommend, with an external Ethernet bridge to my home network. I had an old Airport Express lying around so I use this, set to “bridge mode”, but there are cheaper non-Apple options. If your Ethernet connection is to your network, then you should be able to access the mini directly through that.

I normally drive this via Mac screensharing from my MacBook, but you could use your iPad with a VNC app. The only comment here is make sure the VNC you use gives you enough control over the cursor. Mine (Mocha VNC) is a bit clunky; the keyboard is fine, but the cursor is awkward, or perhaps my fingers are too thick.

If you don’t mind having a keyboard and screen around (I have sitting room constraints…) then I’m sure that would work very well; I did exactly that when first setting up after the gutting of the machine. The power drain would be less; screensharing often takes up half of the CPU demand. On the 2009 mini you don’t have an option to keep Bluetooth and remove wifi- it’s all on the same board; maybe the same is true for 2010?.

With a 2010 mini I think you also have to remove the internal power supply, but if you are thinking of using a different case like Alan, that’s not much of a problem. Over to Alan…

I am very interested in your Mach2 experiences. I first became interested in getting a separate Mini for the audio system when I read some of their publicity, but then I found the Item Audio/Paul Hynes hardware-based approach, and followed that instead, but obviously the best would be to try both. Although M2M have gone under (?), Ultra-fi seem to be doing something very similar. In correspondence with Larry Moore there, he claims that software should be done first, and even suggests that with his setup he can manage without a power supply upgrade (“the right cord is a better long term choice than a power supply.”). However, it’s not clear to me that his “mod” does much more than Audirvana+ does- this also closes down a lot of normal OSX activity while it is running, while restoring it as soon as it drops out.

Question 1 (easy!): how does the SQ with M2M compare with that from the normal mini?

Question 2 (for later, when you have gone down this route!): Which gives more improvement- software or hardware change? Although M2M was expensive, the Ultra-fi cost of having the mini changed is about the same as an SR3, at least if you are shipping the mini within the US.

Cheers

Bob