linear psu for mac mini

[milen007]

hi guys

do any of you have ever tried linear psu on mac mini? i do not understand about things that describe as "isense".

thanks,
Erwin

[Paul_Hynes]

Hi Erwin,

I have been making linear power supplies for the Mac Mini for a while and users are reporting it is avery nice upgrade sonically.

I asume you are talking about the 2009 Mini which has the isense resistor requirement. Here is a link showing you how to deal with isense :-

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

I provide a very heavy duty version (6 to 10 amps) of the PR3 series 3 regulator called the PR3iEHD for diy Mac mini and Macbook Pro projects in voltage settings of 18v5 (Mini 2009), 16v5 (Macbook Pro), and 12v (Mini 2010 and 20011). You will need a big mains transformer (at least 160VA preferably 250VA) and a big heatsink of around 0.7 degrees C per watt. This is because linear supplies are not as efficient as switchers. However the benefits to sound quality are well worth the effort. I use the 12 volt vesion to power an a Pico powered Intel Atom dual core mobo in my audio server. The next step is to fit two more linear supplies for the 5v and 3v3 rails plus any housekeeping supplies and get rid of the Pico, when I get the time.

If there is any interest in this on DIY Paradise for diy builds Yeo might be prepared to stock these modules.

Regards
Paul

[milen007]

wow superb Paul

thanks alot. this is what i need. superb.

it would be great if yeo could stock it. i am interested in one. i think mine is mac mini 2007 which does not have the mini dvi output as the mac mini 2009

in meanwhile i guess i just use LT1083 with big heatsink.

i only need the 18.5v and thats it all i need right for the mac mini?

thanks,
Erwin

[milen007]

hi Paul

may i know the transformer spec you need for the PR3 for 18.5v mac mini? so i can get the same spec that i do not need to change transformer when i upgrade to PR3

thanks,
Erwin

[yeo]

hi erwin

you could deal directly with paul. there is no rule that says got to deal through me just because we are on this forum.

paul is being courteous but seriously i'm okay with paul dealing directly with everyone here.

cheers!

yeo

[Paul_Hynes]

Hi Erwin,

I would use a 500 VA mains transformer with two 18vac secondaries. I do not like running mains transformers near their limits, as they can get very hot.

A 500VA transformer will give you an adequate margin for any additional peripherals that draw power from the motherboard that you may have now or add in future. If you are running the Mac lean with no additional mobo powered peripherals then a 300 VA will be ok.

The two secondaries are important as the PR3iEHD on-board rectification is now organised in balanced mode with a centre tapped secondary to feed it, for both the output stage and the error amplifier power rails. This offers improved performance over the earlier PR3 modules bridge rectifier.

Hi Yeo,

You know that I do not like taking advantage of other peoples goodwill, and I do not like the idea of directly offering goods for sale on other people’s forums unless there is an active market place set up for trade on the forum, so if you do want to stock anything just let me know.

Regards
Paul