Hi,
has anyone explored what difference it makes sonically to power a MacMini (model 2009 with external SMPS), which is used as audio-machine exclusively, with a linear PSU?
Best regards
Stefan
has anyone explored what difference it makes sonically to power a MacMini (model 2009 with external SMPS), which is used as audio-machine exclusively, with a linear PSU?
Best regards
Stefan
Subscribed - I'm interested in this. Anyone know what the power draw is for the Mac? I've been making some linear supplies for some guys at 90W/12V for micro PC's and they tell me its a significant improvement.
That's pretty easy to achieve with an LT1083 based regulation I would have thought - worth a shot
looks as if ppastudio made something like that in a quite impressive way:
http://www.diyaudio.com/forums/pc-based/209500-my-linear-psu.html
http://www.diyaudio.com/forums/pc-based/209500-my-linear-psu.html
Yes I see now, this is a commercial design. Probably the design is a secret.
Is there a well proven plan for a PSU to power a MacMini?
Even though I personally are not very competent about electronics I know enough colleagues to do it for me, if firstly I knew it would be worthwhile and secondly there was a plan that reliably works for this purpose.
What do you think alternatively about variable linear laboratory PSU such as this one:
PeakTech® 6015 A - PeakTech® - Convincing Top Technology
Best
Stefan
Is there a well proven plan for a PSU to power a MacMini?
Even though I personally are not very competent about electronics I know enough colleagues to do it for me, if firstly I knew it would be worthwhile and secondly there was a plan that reliably works for this purpose.
What do you think alternatively about variable linear laboratory PSU such as this one:
PeakTech® 6015 A - PeakTech® - Convincing Top Technology
Best
Stefan
I would not use the lab supply personally -! Would look at a 120VA 12V toroid through audio grade 20,000UF caps and an LT1083 12V reg with 120UF on the input and maybe Tant 33uf on the output. Reasonable heatsinking needed for the reg and good quality short 12V power cord to minimise voltage drop.
Given that the Mac-mini contains several DC-DC converters internally with a compact footprint I would expect these to be the weak point of the power supply.
Of course having said this, if the original power supply is the typical dodgy 'Double insulated' switch mode design with an RF suppression cap between mains and the DC or even a (poorly) Earthed switch mode design which dumps excessive noise into ground then it is possible that a new power supply may improve the sound, when connected to a Sound system or Hi-fi. not due to any inherent power issues with the old supply but more due to grounding problems that PC designers nowadays seem to be completely oblivious to....
(yep I see this a lot with connecting PCes and Laptops to PA systems)
As for using Tantalums across power supplies you do need to be careful doing this, as Tantalum capacitors are prone to failure when subjected to repeated surge currents and besides there are some pretty good Low ESR electrolytics around nowadays.
Of course having said this, if the original power supply is the typical dodgy 'Double insulated' switch mode design with an RF suppression cap between mains and the DC or even a (poorly) Earthed switch mode design which dumps excessive noise into ground then it is possible that a new power supply may improve the sound, when connected to a Sound system or Hi-fi. not due to any inherent power issues with the old supply but more due to grounding problems that PC designers nowadays seem to be completely oblivious to....
(yep I see this a lot with connecting PCes and Laptops to PA systems)
As for using Tantalums across power supplies you do need to be careful doing this, as Tantalum capacitors are prone to failure when subjected to repeated surge currents and besides there are some pretty good Low ESR electrolytics around nowadays.
@ajst2duk
in case you're going to make a list of parts and a schematic diagram for such a PSU, would you mind sharing it?
in case you're going to make a list of parts and a schematic diagram for such a PSU, would you mind sharing it?
There are many (most) on this forum more knowledgable than me but yep I could. Basically I'm just proposing the suggested application design from the manufacturers.
I also agree with RJF in that the primary benefit of such a PSU vs the SMPS is that it is likely to achieve better results for your system through a lower noise floor.
I also agree with RJF in that the primary benefit of such a PSU vs the SMPS is that it is likely to achieve better results for your system through a lower noise floor.
If you are going the LT1083 route, the pragmatist in me would suggest something like:
http://www.google.com.au/url?sa=t&r...qIHQCA&usg=AFQjCNH_fhMT9xDl0NgRy7q4uYzgXPAObQ
or
http://www.google.com.au/url?sa=t&r..._IDwCg&usg=AFQjCNEDeLpU33L4zdIKpwe9pFhfhEHBAg
(makes upgrading parts easier)
Although I am unclear on why both these kits seem to have an output fuse or polyswitch when the LT1083 has built in current limiting (I would suggest linking F1 out)
http://www.google.com.au/url?sa=t&r...qIHQCA&usg=AFQjCNH_fhMT9xDl0NgRy7q4uYzgXPAObQ
or
http://www.google.com.au/url?sa=t&r..._IDwCg&usg=AFQjCNEDeLpU33L4zdIKpwe9pFhfhEHBAg
(makes upgrading parts easier)
Although I am unclear on why both these kits seem to have an output fuse or polyswitch when the LT1083 has built in current limiting (I would suggest linking F1 out)
If the primary benefit of a linear PSU is lower noise floor that penetrates the rest of the hifi system, wouldn't a mains filter between computer-psu and plug connector have the same outcome?
There is a company here in the US called Pi Audio in New Mexico that offers a replacement power supply, a upgraded mac mini cord, and a full on battery operated model. I have used the upgraded power cord and there is a significant change for the better when it comes to noise. Also, the battery powered ones offer even more of sonic improvement. I currently have everything on batteries, except for my Mac Mini. He has a site over at audiocircle.com
Jon
Jon
you might think so, but the problem is that switchmode can be inherently noisy (but then the same can also be said of computers in general) so they have to do something with that noise.
a 'double insulated' (two prong power cord) supply will typically have a Y class capacitor* between low voltage 'ground' or common and AC mains in an attempt to filter that noise to earth. Of course this also means that noise can flow back the other way to the ground on any audio gear connected to the computer.
Grounded switchmodes still have noise suppression capacitors, but now those capacitors are connected to ground, and while this arrangement usually works quite well it does mean that in some cases you can end up squirting extra noise into your audio ground (which will be connected to this mains ground).
A mains filter will usually have series inductance to increase series impedance to higher frequency noise but will also have capacitors to ground, which may just make ground noise worse by increasing the noise current. In fact usually computer power supplies have mains filtering built into them already.
In my experience it is usually laptops etc with 'double insulated' supplies that cause most trouble, but usually connecting them via a 1:1 mains isolation transformer cleans them up nicely as this now breaks any noise current paths between ground and mains.
In general a good mains isolation transformer can often solve a lot of audio ills, er, noise problems for relatively low cost and little effort.
* Y class capacitors are supposed to be self-healing and inherently safe, of course I have not started the discussion about if cheap Chinese equipment (think self igniting Iphone chargers off Ebay) is using real Y class capacitors, or merely cheaper capacitors with the letter Y printed on them. 😱 ....
while I am very cynical about magic cables that someone has left in a fridge over night, running equipment off batteries will break any earth current/noise, often leading to noticeable improvement.
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FWIW, I have been in touch with Dave at PI recently regarding what the options were with my 09 Mac Mini. His suggestion was a HDD SMPS Buffer that had an option for additional outputs. I'll let Dave quote pricing but let me just say that it seemed reasonable.
The other option is a linear power supply around a $1000. I have concluded from people "in the know" that the MM '09 isn't worthy of the expense.
I would also characterize opinions as less than enthusiastic about battery supplies for MM 09's.
I was looking at rigging up one of these Carnetix to plug into a battery supply, but I decided the hassle wasn't worth the improvement. BTW, there are interesting reads regarding the subject of computers in Auto's. As you probably know, the Auto enthusiasts are nuttier than audiophiles.
The other option is a linear power supply around a $1000. I have concluded from people "in the know" that the MM '09 isn't worthy of the expense.
I would also characterize opinions as less than enthusiastic about battery supplies for MM 09's.
I was looking at rigging up one of these Carnetix to plug into a battery supply, but I decided the hassle wasn't worth the improvement. BTW, there are interesting reads regarding the subject of computers in Auto's. As you probably know, the Auto enthusiasts are nuttier than audiophiles.
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