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Linear Power Supply or Battery on Mac Mini - pics

Posted by AbeCollins on December 21, 2014 at 18:27:01:
So here's the setup. I'll be comparing the TeraDak 12-Volt 10-Amp linear power supply against the stock switcher that was removed from the Mac Mini. I will also compare against a 12-Volt battery. Results will be posted later in the week.

PS Audio NuWave DAC, Mac Mini, TeraDak Power Supply, ARC VSI-60 Amp, Tannoy Definition D500 Speakers.
- iPad Visual Remote Control, Mac OS X 10.8.5, 24/96 AIFF files on Mac, Audirvana Plus: Memory Play, Exclusive access
mode, Direct mode, Integer mode, SysOptimizer.
TeraDak 12-Volt 10-Amp linear power supply powering the Mac Mini. Power supply heat sinks don't even get warm
as the Mac Mini is drawing less than 9-watts while playing music. The Mac Mini case remains cold to the touch.
Decided to try a 12-Volt battery on the Mini just for grins. And why not since it's so easy to do now that the Mini
requires only +12VDC for its external power source.
Attached my cheap 12V 7Ah SLA battery I had lying around. Saw nearly 6-Amp peak current draw during bootup
then down to less than 9-Watts power consumption while playing music.

Here's the output of the TeraDak linear power supply under 1-Amp load measured before the additional filtering
within the Mac Mini. Noise is about 1.5 mV-pp (0.53 mVrms), not bad at all.

Here's the output of the battery under 1-Amp load. Noise is bit over 3 mVpp (1 mVrms), still not bad but not as
good as the TeraDak.

Here's what's at the output of the TeraDak power supply with the Mini turned ON*. The battery looked
pretty much the same. This is noise generated by the computer, not by the power supply itself.

*20MHz BW enabled on scope otherwise too much 'fuzz' to be viewable and time scale changed to 10mS/Div.
The scope screen shots below were just added 22:25 PST. Was able to get a better periodic waveform to trigger on
when I turned on a screen saver on the Mac Mini.
Transient voltage 'droop' on the TeraDak 12V linear power supply.
Transient voltage 'droop' on the 12V 7Ah SLA battery. The battery is better in this regard.
The battery appears to produce more wide band noise under a steady state DC load. However, the battery proved to be 'stiffer' in terms of transient loads.