Mac Mini Power Supply

If I may ask, what type of PS did you build? I've debated on buying or building one, and am debating on how far one needs to take it.

I am surprised a linear power supply made any difference at all!

Min,

Can you build me one?

What difference did you hear?

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.

Thank you Mintzar!

If I may bother you further, did you just follow the data sheet schematics for the LM 338? I realize that one can never take a PS too far, I guess what I was curious about was "how far" you need to go to get the noticeable improvement you commented upon.

I know a couple of people that use the Ultra-Fi ECM in their MAC Mini based digital rigs and they feel it is a tremendous upgrade. Here's a link to one that is currently for sale. I'm not affiliated with this seller (don't even know him), but I do know the manufacturer and a couple of his customers who use the ECM. I'm not endorsing the product as I haven't heard it yet. Just passing along some information......

http://www.audiogon.com/cgi-bin/cls.pl?powrcond&1284048765&/Ultra-Fi-ECM-music-server-cond

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).

Before spending money on power supply or expensive power cord, please try the snap-on ferrite cores first to reduce digital noise. Just snap one on each end of all your power cables and digital cables. They are very effective and cheap.

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.

"I have always found switchmode supplies to be VERY noisy and mechanical sounding."

I don't question your findings but I hope you realize that this voltage (is it 18V?) goes inside of Mac Mini thru internal switching regulators to deliver voltages for micro and rest of digital circuitry.

Linear powers supply is also a switcher operating at 120Hz. It takes current from mains in very narrow current spikes of big amplitude. Width of the spikes depends on the load.

Switchers got bad rap from cheap computer power supplies but realized properly are not only very quiet but also line and load regulated (class D is switching mode supply). High switching frequency is not audible and easy to filter out. For that reason Jeff Rowland uses switchers in Capri preamp.

Where would one find plans to build this psu and a parts list? I'm intrigued by this idea. Thanks Mintzar.

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.

Mintzar - I don't know of a single switching mode power supply that operates in audible band. The lowest I know to operate is about 50kHz - non audible. Modern switching power supplies are switching at zero voltage/zero current while linear power supply switches at max voltage.

As I understand it you need about 6A for this supply while LM338 is rated only 5A (continuous). Linear regulators are noisy, require huge transformers are most often unregulated. They are also not as easy to design as it seems. Older regulators like LM338 are sensitive to output capacitors' ESR - might start oscillating when ESR is too high but also oscillate when it is too low.

"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." - Only for efficiency sake. Fast switching brings more noise pollution.

As for designing with LM338 - I did it over 20 years ago and would not do it again. LM338 is really old stuff. I requires almost 3V input output differential making it total of 8.5V drop across regulator if you provide for +10/-20% line variation (3V +18.5Vx0.3). This means 8.5V x 6A = 51W (big heatsink). In addition LM338 has very poor ripple rejection equal 0dB (none) at 100kHz. You can do much better with modern regulators. Transformer is also a problem because 110 W supply requires almost twice rating because of the nature of load. Current spikes from bridge/capacitors have much higher RMS value than average value heating copper (windings) while high frequency content is heating the core. If you need to deliver 110W with 50W lost in regulator I would pick at least 250W transformer.

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 have the ECM and I would say it rolls off the highs. It makes digital sound less harsh and biting. With the ECM the highs sound more organic/analog. Can anyone explain how this is done with the transformers in the unit?

I don't think it really is a power supply.

I do have an adapter hooked up the the power supply of the Mimi that allowes me to use a high end power cable. Needless to say the PC does makes a huge difference from the stock cable.

What kind of $$$ are we into with such a power supply?

Congrats on building your power supply. I for one am convinced that proper power supplies can make a huge difference. For those not mechanically or technically inclined, Bolder Cable makes a nice ps for the mini. It's a bit pricey ($625.00).

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.

Could you tell me how I can go about upgrading the power supply for my Mini? I am not skilled on computers at all.

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.

07-20-10: Glory
I have the ECM

Glory,

What are the components of your digital music server setup? Mac mini? What DAC, Hard drives, cables, etc.? I'm just curious because I don't think many people would be familiar with the ECM unless they were Ultra-Fi customers or friends.

I live near the builder/designer and I have a couple of friends with full Mac Mini and Ultra-Fi solutions. The sound is outstanding IMHO.

Weiss Minerva,VD Ultra Clear wire, Atma-Sphere S30/Dude pre.

I did again A/B the ECM and with it the music has less of a digital sound. More body and fullness for sure. With out it the sound has a thinner presentation.

I just ordered a Mac Mini (MM) linear power supply from Mintzar based on my own favorable experimentations with isolation transformers for my MM and a linear power supply for my DAC. I'll report back my experience. Mintzar so far has been a complete joy to deal with, knowledgeable, passionate, responsive.

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!

I received my MM LPSU (Mac Mini linear power supply) from Ryan (Mintzar) this week. Color me from Kansas on this - I was highly skeptical about what, if any, incremental improvements this LPSU would yield in my system.

To recap my baseline, I use a PurePower 2000 to feed power to my Metric Halo LIO-8 DAC. The stock MM SMSP is plugged into an isolation transformer which in turn is plugged into the PP2000. My amps are powered by an Elgar conditioner on a dedicated 20 amp line. Pretty decent degree of isolation.

The improvement Ryan's LPSU made was immediate and obvious in the first few seconds - a significant reduction in glare/bite most noticeable on leading edge transients and the upper range of female vocalists, an increase in across the board resolution and greater tonal density (i.e. instruments and vocalists were more fully fleshed out).

By chance, a friend stop by yesterday for a visit who had heard my system a couple months back. The only change is the MM LPSU. He immediately picked up on the improvements as well on a Loreena McKennitt track with which he is very familiar.

Aside from my satisfaction with the LPSU, his customer service has been exemplary. From a disclosure standpoint I have no personal or financial ties to Ryan.

Bottom line, having now heard the improvements I could never go back to the stock SMPS - it sounds bright, edgy and unnatural in comparison. As a next step I've ordered a LPSU from Ryan for my LIO-8 - I'm skeptical about that as well... I'm also going to audition a Mo-Jo power cable based on Ryan's recommendation.

Over on Audiocircle.com, people are claiming that a stock 2010 Mini sounds better than a 2009 Mini with linear PSU.

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.

Why spend $400.on a linear PSU, when you can have better sound,lower power consumption and less boxes and cables by upgrading to a new Mini.

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.

Mintzar, unlike you I'm not trying to sell linear power supplies.

I don't own a Mini and I don't plan to buy one.

If you want more info, go to audiocircle and read the posts from people that have compared the 2010 Mini and 2009 Mini.

813,

Wow. Down boy, down.

Aren't we cranky today.

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.

Glory-

Mintzar can't think of any reason that putting the supply internally in the Mini would make it better because he's trying to sell external linears.;-)

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.

Mintzar-

I'm not trying to pick a fight.

I just asked, why spend $400.on a linear PSU, when you can have better sound,lower power consumption and less boxes and cables by upgrading to a new Mini.

Isn't that a positively fair question?

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.

"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."

Based on all the reports I've read it does.

I place just as much faith in these reports as you and others claiming that your $450. power supply makes "a substantial positive difference to the 09 mini."

There's no proof that- "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."

It's very obvious that you started this thread as a fishing expedition to help sell your linear PSUs. If your PSUs are so good, pay for an audiogon listing.

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

Mintzar- are these still available?

Try Core Audio Technology. I have Mintz power supply for my mac mini. Smooth. steve

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 :)

Hey Mintzar,

FYI, your link above - http://www.circumpointaudio.com/ - does not work.

Since the new, wonderful audiogon no longer allows members to email each other (in their defense, I can see member emailing quickly leading to anarchy), please contact me through one of my ads and let me know if you're still selling these linear PS's, and if you also handle removing the switcher from the Mini. Thanks.

Paul - to be clear - "Mintzar" is, in fact, the proprietor of Core Audio Technology. Check out his website and contact him, and thank me later...

hi Ryan

what voltage and current draw does the mac mini need? where do you find the mac mini power connector?

thanks,
Erwin

The mini runs on 18.5Vdc and draws no more then 6A.

Connector and cable can be purchased fronm here: http://store.mp3car.com/MacPac_Power_Cable_Kit_For_the_Mac_Mini_For_Mac_Mi_p/cbl-086.htm

Wiring here: http://www.computeraudiophile.com/files/Mac%20Mini%20PS%20Cable_0.pdf

I just saw this post, sorry for the delay in response...

Power supplies can be ordered through Core Audio Technology's website or contact me from there. Plenty of reviews on the Core Forums also.

Yes, I remove the switcher and insert an additional filter inside the mac mini chassis. My power supplies are then run externally.

I buy a stock PS brick, chop off the cable and add the necessary caps and resistors to make it function.

"I buy a stock PS brick, chop off the cable and add the necessary caps and resistors to make it function."

Why do this if you can purchase a new cable?

It's cheaper than buying the cable from MP3car most times.

And I build my cables into a Powercon for my power supplies so I'd have to chop things up a bit anyway. Unfortunately it bricks the brick to do this so it's a bit of a waste, but there aren't many cost effective alternatives for older Mac Minis.

I wasn't able to find a cheap power brick for my Mini, so I bought the MP3car cable. It works fine.

There is more than one wiring diagram around for the connector. The right configuration has the iSense cable running to ground through a 3.3K resistor. A quarter-watt one is fine.

There are a good many aftermarket power supplies around, or were. I chose a 2009 Mini as being the most recent model that still had an external PS. Easier to work on, adequate for the purpose, and probably easier to resell/reuse too.

I did all the software tweaks, maxed the RAM, put in an SSD and found a linear PS for the (external, FireWire 800) music drive. That PS was a 12V Acopian Gold Box model from eBay.

Finding a power supply for the Mini was hard. I didn't want to pay a lot because I had no proof it would really make a difference, aside from the small improvement in clarity and coherence I got when I upgraded the hard drive's PS.

Eventually I found an 18V Acopian Gold Box A with +/- 0.5V adjustable output voltage, at a price I was willing to pay. It was an older unit but Acopian worked very kindly with me to get it running. It needed new filter caps. These were not hard to find.

My total cost was under $150 and the improvement was, IMO, worth while. Timbres are sweeter, highs are cleaner and the music seems more coherent.