Mac Mini Power Supply

Shoot me an email and I'll gladly give you some places to start. If you aren't tech savvy or haven't worked a soldering iron this project isn't for you. However, I am more than happy to build them.

I heard a bigger difference in my system than upgrading an amplifier.

I built a linear PSU based on the LM338 regulator. I used Nichicon Muse caps and built a power supply that could probably be used for a decent solid state amplifier. WAY overkill -- if there is such a thing when it comes to PSUs.

I have always found switchmode supplies to be VERY noisy and mechanical sounding. Switching to a nice linear power supply for the mini was like night and day, I couldn't be happier.

I can build more, sure. Send me an email and I'll figure out what it cost me to build it and give you a price.

I'm not a tweaker in the sense that I don't like making changes to my system that are debatable. I like tangible changes that anyone walking into the room would hear. I would go as far to say as anyone using a computer for audio NEEDS a linear power supply to get the most out of their system, given the price-performance ratio of the upgrade it's a no brainer.

As far as "how far one needs to take it"...

I'd say the higher quality the better. Nichicon Muse are what I consider my "middle-end" caps.

At some point I'll probably build a Mini PSU using Jensen 4-pole caps ($90+ each) like I use in my amp. But that's a monster power supply that I've only seen in $30k+ amplifiers so if ANYTHING was overkill for a Mini that would be it.

If you are going to build a PSU yourself make sure you have proper tolerance parts. They need to be able to handle the 2-6A that the Mini draws depending on the peripherals attached. That means rectifier diodes and regulators need to be appropriate. There is also an "iSense" connector that needs a resistor attached to it.

If it's a project you're thinking of undertaking I'm happy to recommend some parts as well.

I use Isolation transformers in my system that I modified to great benefit. I am yet to find a power conditioner that works better than the Isolation transformers. The ECM is a transformer-based conditioner. So I imagine it's decent. I just use hospital grade TXs made by Topaz, which are considerably better than the ECM (though bigger, heavier, and uglier).

I partially followed the datasheet for the LM338. I used a LM337 for the negative rail (which doesn't draw much current, I believe it's only duty is iSense).

I think just going from a switchmode supply to a linear supply would give a great benefit, I just wanted to take it a step further and put some decent parts in the supply.

There's a few regulators based on the LM317 that you can just do a parts swap (with a little research).

Ferrite cores are a fairly standard trick. They are cheap and while they will filter out some noise, they are no replacement for a proper power supply IMO.

I personally don't like them because they greatly limit dynamics. I also found that the ferrite cores did very little when attached to the mac mini stock power supply.

You will also want a rather large ferrite core to make it effective. I have found that Neodymium magnets filter better than ferrite cores only they don't limit dynamics. Granted, I am still skeptical of magnets and am doing further tests to make sure I wasn't just hearing things.

You are correct, Kijanki.

Switchmode supplies in many products on the market DO NOT have their switching frequency above the audible spectrum, however. Mac Mini included.

My amplifier is a Class D amplifier with a Linear PSU. The switching aspect is well above the audible spectrum. EVERY switchmode supply I have heard was noisy compared to a linear supply. Companies like Bel Canto, W4S, Nuforce, etc all use switching supplies and are incredibly noisy and dry sounding. Granted, most companies don't put expensive power supplies in their gear, it's just too expensive to manufacture for a large company.

The power coming from the wall is the power used to create every signal in your audio system. Better in = better out. And if you build a better supply for your source you start with better. If you start with an amplifier, but have a crappy source the signal can only be as good as the source.

Switchmode supplies with a switching frequency in the audible spectrum have a moment where zero current flows, the lower the switching frequency the more noticeable those periods of off time become. Ideally you would want the switching frequency to be so fast that it would be impossible to tell when it turned off and back on. The off periods are why switchmode supplies sound noisy and often mechanical.

As for the Mac Mini PSU. There are no plans or parts lists. This is a design that I did the research for and constructed myself. The only tidbit of "plans" are the pinout for the iSense DC connector for the Mini. What I can tell you is that you need to build an 18v5 PSU capable of outputting 6A. What I do is build a 22V PSU and regulate it down to 18v5. That means the regulator, resistors, capacitors, and diodes all have to be able to handle 6A of current (preferably something like 10-12A MINIMUM for safety).

Send me an email and I can potentially get you started. It took some trial and error.

I use a 300W transformer. The LM338 can handle up to 12A. Since the Mini uses 6A MAX it works just fine. The Mini actually idles around 2-4A 99% of the time.

I am not using the LM338 as a standalone regulator. My next project will be to use series regulators to get more current output. But that will be a VERY serious PSU.

At any rate, the ESR of the Muse caps is perfectly fine for the LM338. The PSU has been running perfectly fine for the past four days. If it was going to fail it would have done so already. The first power supply I built failed within five minutes.

Old doesn't mean bad. We are still using the same math developed by western electric YEARS ago for everything audio. Many vintage pieces of gear STILL sound better than modern gear.

Is there better? Of course there is. There's always better.

However, I wouldn't shoot down an option without giving a better alternative.

I borrowed the boulder supply from a friend of mine, one of the reasons I wanted to build one myself. My supply had a much larger impact on the sound, but both are very nice pieces of gear. I was offering to build my supply to a few people for $400.

As I understand it, the ECM uses Balanced power transformers. That means rather than having 120v on the hot conductor and 0 volts to ground on the negative, you have +60 and -60, which are out of phase. In theory that cancels out common mode noise in the same way balanced analog circuitry works.

While I can't say for certain, almost ALL power conditioners that boast a "more analog" sound are using suppression capacitors and ferrite cores. Ferrite tends to work fairly well on digital gear for rolling off what people consider to be digititis. Ultimately it's a cheap trick, but has poor tradeoffs. I'm yet to find a power conditioner that can hold it's own against a Topaz Isolation Transformer with 146dB common mode noise rejection.

People may say a better mac mini power supply makes the sound more analog-sounding. I personally just think that the power supply, and more accurately the non-linearity and ripple caused by crappy power supplies is what causes a piece of gear to sound digital.

Analog is just digital that's been pressed to LP.

Thanks for the kind words, Earflappin. Your email evaluation earlier made my day. Wasn't expecting such overwhelmingly positive feedback. I'm looking forward to reading your final evaluation and hearing about your demo!

Thanks for the kind words, Earflappin. It's truly wonderful to hear that you had such great results. And that I'm not hearing things!

Just an FYI, I haven't sold any PSUs to anyone on acircle. So if they are comparing linear PSUs to a stock SMPS they aren't comparing mine. The Boulder and PH Design PSU use good regulation, but inferior parts and filtration everywhere else compared to my supply.

That isn't to say the new SMPS in the 2010 Mini is bad or that their claims are untrue. I'm just trying to be fair in what is being compared. An HP bench supply may be a linear supply, but it's highly unlikely that a bench supply will sound better than the stock SMPS. Bench supplies are designed for adjustability and testing, not for audio purposes or clean power.

The new Mac Mini has a new video chip that's better. So if video is your thing you will get some benefit by going to the new mini for video.

I've read that there's virtually no audible difference between the 2010 Mini and the 2009 Mini, both with stock parts.

I can think of no reason that putting the supply internally in the Mini would make it better. If anything, you would have more power supply noise leaking into the motherboard. The supply would be smaller, have less filtration, and more issues from switching noise.

Kana, I'd love to hear more about the comparisons that were done and what supplies that were compared. It's difficult to give your statements foundation without a little concrete to back them up. If the new Mini really IS better
It'd be great to know why.

Thank you for posting your comments about the 2010 Mini, I (and I'm sure this goes for other people reading the thread as well) appreciate the opportunity to be able to do more well-rounded research and comparisons.

Bare in mind, the 2010 Mac Mini compared on the Acircle thread was decked out with all kinds of modifications and specialty software. The people who compared stock to stock heard no difference or a small difference.

Thanks Glory. 813, I'm not sure why you're trying to pick a fight. I've been respectful in answering your accusations here and on CA forum and I'm trying to be as informative as possible in doing so. If you read my initial post I didn't originally intend on selling these supplies and I make very little money doing so. I am doing it to help people have better sound, since it's so difficult to find these days.

Since you don't own a Mac Mini and aren't interested in one it appears that you are making trouble for trouble's sake. I would appreciate it if you stopped doing so and began posting positively to what was a very useful and informative thread. Or don't post at all.

It was a perfectly fair question and I answered it.

It is also somewhat rhetorical.

Why spend $400 when you can get better sound, lower power consumption, and less cables? There is no reason to whatsoever. If all those things were true and you could pay $400 for the new mini rather than $400 for a PSU upgrade then that would be a no brainer.

The problem is that the new mini doesn't necessarily sound better than the 09 mini with or without upgrades. It might, it might not. The only facts of this equation are: one, that my power supply is $450; two, it did make a substantial positive difference to the 09 mini; and three, that the 2010 mini starts at $700.

So if someone asked me what would make a more worthwhile difference: upgrading the power supply on the 09 mini for $450 or buying an entirely new computer for $700 I would say that's a fairly simple decision. The mac mini supply can always be resold for nearly what you paid for it, it's much more difficult to get your money out of a used computer.

However, if you wish to argue that a $700 upgrade outperforms a $450 upgrade then I think that is perfectly fair. It certainly is a more expensive price tag and one would conceivably think it should perform at a higher level.

By wgscott: "I upgraded from 2009 to 2010 mini the day it became available. It was a huge improvement for video. I haven't noticed any difference in sound quality from the 2009 version (both had stock power supplies and were off-the-shelf standard components, no modifications). So I would take reports of a dramatic improvement with a grain of salt."

There were similar reports on the acircle threads. The only person to have tested an aftermarket power supply on the mini was Eric of DB Audio labs. He sells the Tranquility DAC for a living and this was posted on a Tranquility thread. He also did not mention what LPSU he tested or if he even tested one, just that it would beat any modded 09 minis.

From what I've read there has been only one test that was run between the 2010 mini and the 09 mini that had results that were favorable to the 2010 for audio.

I'm not bragging that my LPSUs are "so good." If they were perfect I wouldn't be working on a higher end supply. My only comment was that you are comparing apples to oranges... two differently priced units for two different applications.

My purpose for this thread was to raise awareness about the performance benefits of upgrading the mini's power supply.

I totally understand people's apprehension at purchasing an aftermarket power supply and the performance benefits thereof. If they are concerned, they are welcome to email me. The best I can do is give them references, offer returns, and describe the technology. If you aren't convinced then that's no sweat off my back, I'm just trying to help.

Your points are becoming redundant. I appreciate you playing devils advocate so that people browsing the thread can do ample research. It is important that they see alternative options for their upgrade paths. We now understand that someone could upgrade their PSU on the 09 mini or buy a 2010 mini. I could go as far as to say that they would both benefit someone's audio system. Which is "better" cannot be debated without further testing.

So unless you have more information to provide or a new point to make, I'd appreciate that you stop attacking everything that I say. I have not once attacked your character, so I'd appreciate it if you didn't attack mine.

A few updates...

My high-end power supply is now available. I also have a few modifications under way to allow the 2010 Mac Mini to function with my power supplies.

I have had quite a few requests over the past few months about my amplifiers and power supplies so I created a website. It's very much a work in progress, but at least it's something to read. Circumpoint Audio

Yes, the power supplies are available... but VERY different from what they were when I wrote this article a year ago. Take a gander at the website and shoot me an email and I'll help you any way I can :)