[Paul Hynes]

I can now build a high performance, very low noise linear power supply in the SR7 format that can be used to replace the internal switching power supply for the 2010 Mac Mini when used as an audio server, which is specified to draw 85 watts when fully utilised.

There are two options available. The SR7-12 is rated at up to 7 amps continuous 20 amps transient, and the SR7EHD-12 is rated at 10 amps continuous 40 amps transient for those who are using more power hungry motherboards for their audio servers, or who just like to have some additional reserve in their power supplies.

The SR7-12 costs £525 and the matching DC7C high current, high performance DC lead costs £45. Insured carriage and packing will be charged at cost.

The SR7EHD-12 costs £650 and the matching DC7C high current, high performance DC lead costs £45. Insured carriage and packing will be charged at cost.

The Mac Mini will need dismantling to remove the switching power supply and fit a new DC connector in place of the mains inlet on the chassis. This is a complicated and time-consuming process demanding care and some hands on knowledge of computer assembly. For those without this knowledge or the time to do this I am prepared to do this for £100, which includes a high quality, suitably rated chassis connector, that mates with the DC7C lead.

The SR7-16.5v will provide 4.5 amps to power the MacBook Pro and the SR7EHD-16v5 will provide 8A for those wanting the heavy-duty version of the supply.

The SR7-16v5 costs £525. Insured carriage and packing will be charged at cost.

The SR7EHD-16v5 costs £650. Insured carriage and packing will be charged at cost.

The MacBook Pro uses a power supply with a DC lead fitted with the proprietary Magsafe connector. This lead can be adapted for use with the SR7. Adapting the Macbook Pro DC lead costs £25 and customers will have to provide the Macbook switching power supply to enable this to be done.

Regards
Paul

[wgscott]

That sounds promising. Is this 120V/60Hz compatible?  Since the 2010 mini consumes very little power (~10 W idle, ~12 W with both processors maxed out), why the need for the high-current power supply?

What sonic improvement is realized?

[jtwrace]

How does this compare to a battery supply version?

[Paul Hynes]

wgscott

There is a mains voltage selector switch allowing use on 120V/60Hz fitted to the back panel.

Apple stated that the latest Mac Mini has a low idle power requirement of around 10W continuous. This can increase with application processing, up to a maximum of 85 watts continuous, with full utilisation of all applications. The actual power for audio processing would be relatively low with current audio applications although I suspect this could increase somewhat with Hi-Rez processing in the future.

Why use a high current power supply? If you tried to get away with a 20 watt power supply I think you would end up frustrated with data dropouts and power supply induced jitter caused by insufficient current to allow the data waveform to slew at the speed required in the processing circuitry when peak processing power demands are not met. If you are prepared to accept this you could use my SR3-12 power supply at around half the cost.

Compared to the SR3 the SR7 has a lower output impedance over a wider bandwidth and a much larger custom built audio grade transformer with an oversize core designed for silent running and large transient current delivery. The SR7EHD has an even larger transformer and more energy storage. A simple analogy would be the SR3 is equivalent to a Ford Mustang, lively and exciting but somewhat limited when you really push. The SR7 would be the equivalent of a Bugatti Veyron, a powerful car that is effortlessly responsive demanding driving conditions, and the SR7EHD being equivalent to the Veyron sports version with even more performance. All three will give an enjoyable experience but I know which one I would prefer to drive.

As for sonic improvement you can expect a more stable image under all dynamic conditions with better musical timing and structure, less veiling and much less “digital glare” effect allowing you to get closer to the musical performance of the musicians. You should also be able to listen for extended periods without feeling fatigued assuming of course that the rest of your system is not contributing to the fatigue effect.

Jtwrace

The SR7 compares very well with a PR3HD regulated battery supply, as the regulator is the same circuit topology. Any differences are very subtle in the higher frequencies. The high current drain on the battery is a pain to deal with manually and commercially the battery supply is more expensive to provide because of the battery management required for safe operation as well as the overall structural requirement.

Regards
Paul

[Paul Hynes]

wgscott

There is another reason for a larger better power supply if using the Mac Mini for home theatre use. The increased processing requirement for HD Video and Audio will need more power. The more functions you are using, the more important it becomes to have a fast quiet power supply to allow all the processing to continue unimpeded.

You can expect a very noticeable improvement in picture quality as well as the sound quality improvement with the SR7 powering the Mini.

Regards
Paul

[wgscott]

Paul:

Thanks, especially for the additional comment.  I am also asking because I do graphics-intensive (including hardware stereographics) stuff on macs at work.  I've always bought the best graphics card I could obtain, but I never gave a second thought to the power supply. I just assumed that it would be fine.

[poseidonsvoice]

Paul,

These are excellent developments and I am very pleased you are bringing this to the market. Will you be able to sell only the shunt regulator version of the SR7-12 for those of us who can source/build our own basic power supplies?

This should really make this a state of the art digital transport with all the attendant advantages of the Apple Macintosh platform, i.e. Itunes, Pure Music 1.8, easy configurability and remote control via a Ipad/Itouch, etc...

Best,

Anand.

[Paul Hynes]

Hello Anand,

In the SR7 I have used my best high performance series regulator topology to allow a high quality, very low noise power supply, without too much size penalty and for a reasonable cost.

See Serengetiplains comments on the resulting sound quality with the Mini at :

http://www.audiocircle.com/index.php?topic=82369.40

The SR7 uses the PR3iHD regulator module, which is available for £120 plus shipping. The SR7EHD uses the new PR3iEHD module, which costs £140 plus shipping.

A 12 or 18v5 shunt regulated power supply for the Mac Minis spanning a 6 amp load range (from 1 to 7 amps) would require heavier thermal engineering, in a larger case, which I can do if requested. Unfortunately it would add around 50% to the cost not to mention the additional shipping cost due to the weight/size increase.

The SR1MR module will not cope with the level of power dissipation that would be required whilst the Mac Mini is idle and only drawing around 10 watts. Remember that the shunt regulator module is the equivalent of a pure Class A amplifier. I can provide a custom-built high power shunt regulator module that will cope with power range requirement of the Mac Mini. I would expect this heavy-duty shunt regulator module price to be approaching  £200.

Regards
Paul

[poseidonsvoice]

Paul,

No worries, I assumed that the regulator in the SR7 was a shunt regulator not a series regulator. I would be more than happy with a series regulator for this particular design since the current requirements are so high. The second reason I would be happy with it is because *you* designed it. I will probably consult you on the details of the passive ps that would be implemented prior to the series regulator (PR3iED).

I might end up ordering both the PR3iED for the Mac Mini diy ps, along with my already settled order of shunt regulators for the Buffalo II/III dac. That would save some in shipping for me.

All the best,
Anand.

[larevoj]

Hi Paul, how is SR7-12 different from the SR7-18v5 I ordered in May?? Can SR7-18v5 sustain a high transient draw too? 

[Paul Hynes]

larevoj

The SR7-12 and SR7-18v5 use the same regulator, transformer and hardware. They are just set up for maximum efficiency at different output voltages. This means different transformer secondary voltages and capacitor voltage ratings.

The SR7-18v5  can source 20 amp transients.

Regards
Paul

[larevoj]

Great! Can't wait to hear it!!! 

[serengetiplains]

Just to add a few comments to those I posted in the other Mac Mini supply thread, there are two possible sources of improvement in replacing the switcher powering the Mini.  The first and most direct is improvement wrought downstream of the replaced switcher, that is, in the Mini circuitry and the signal it outputs, and in any components fed by the Mini whose ground plane can be affected by the Mini's ground (very dirty in the case of a switcher-powered Mini).  The second source of improvement is that wrought by removing an EMI/RFI radiating source (the switcher) from the power circuit that powers other components.

I run my system through series power regenerators, such that I have a dedicated regenerator for each component (computer, USB converter, amp) that is itself fed by another regenerator.  Given this, improvements I hear by having replaced my outboard switcher with Paul's supply are likely almost entirely improvements of the first type above, to the signal the Mini outputs + cleaner ground plane.  The latter is probably a very small contributor because my USB to SPDIF converter galvanically isolates the USB receiver circuitry from the remaining circuitry.

All that said, one can then assume that the improvements I heard were largely improvements to signal integrity.  Those who haven't my setup (the regenerators, galvanic USB isolation) can expect somewhat larger improvements overall, therefore.

[larevoj]

Hi Serengetiplans, would you have a couple of pictures to illustrate how your MM is setup? 

[serengetiplains]

Hi Larevoj, there's not much to see, but here it is, my Mac Mini tucked into a small corner in my room perched atop the supply I purchased from Paul.  There's a small, 8" cord I snipped from the Mini's outboard switcher supply connecting the current supply to the computer.  That's it!

[serengetiplains]

And here is my seriously reworked USB to SPDIF converter, an Empirical Audio Pace-Car.  I've added separate shunt supplies to feed the two internal clocks, + three series supplies each feeding a shunt supply powering the converter's digital circuits.  A few mods remain to be done.  One is to add an outboard 5V supply to power the USB receiver chip---this duty is now performed by the computer through the USB cable.

Notice the plastic-film bypass capacitors wayyy away from the supplies they bypass.  I haven't decided, listening-wise, if they're doing more damage than good considering the appreciable inductive reactance of the leads.

There is a fourth r-core transformer glued to the outside back of the unit ... no room at the inn, cough.

[larevoj]

Wow...thats quite an impressive work you got there 

[serengetiplains]

Thank you, larevoj.  The transformation wrought by replacing stock supplies with cascaded Hynes supplies was remarkable.  Digital glare---that bright, edgy digital sheen---vanished almost entirely leaving soft-sounding highs and articulate lows.  It took me 10 years to find that soft digital sound---soft in the sense of an absence of digital glare.  Attention to power supplies was the key.

[PeterBurrows]

I have just received a Macbook Pro power supply from Paul and I have to say that the difference that it has made to my system is amazing.

The sound is more detailed, fuller, vibrant and extended at the higher end in particular without any hint of harshness or fatigue.

I would not hesitate to recommend this as an extremely worthwhile and important upgrade to a Macbook Pro.

Peter