Macbook Pro use power supply ac or 3 prong?

Patrick B. · 8th May 2008

I had a screen glistch with my alphatrack usb controller.
The issue was tracked down to the power supply of the macbook pro.
I was using the ac plug that goes onto the power supply.
After removing the plug and using the 3 prong cable that came with the macbook the issue was solved.

After realizing I had previously used the a/c with no known problems, I just wanted to post this and ask what is better for macbook pro users when recording audio through firewire or usb devices. Is the 3 prong better than the a/c?

skymaster · 12th May 2008

Hi Patrick,

Using the cord extension rather than the little flip up AC connector just adds a ground connection to the power supply. This is generally a good thing regardless, to drain noise from the switching power supply away. Without it you were probably getting noise on power input which the AlphaTrack didn't like. I have also found that the connections in the flip up connectors get intermittent over time anyhow, or they don't stay securely in wall outlets. I tossed mine and went to the grounded cord a long time ago.

Also, some Powerbooks (I think the older/cheaper models) came with a completely non-grounded power supply. Its easy to tell those as the extension cord only has the 2 pins.

8th May 2008	#1
Patrick B. Gear Head Joined: Mar 2008 Location: CA Posts: 46 Thread Starter	Macbook Pro use power supply ac or 3 prong? I had a screen glistch with my alphatrack usb controller. The issue was tracked down to the power supply of the macbook pro. I was using the ac plug that goes onto the power supply. After removing the plug and using the 3 prong cable that came with the macbook the issue was solved. After realizing I had previously used the a/c with no known problems, I just wanted to post this and ask what is better for macbook pro users when recording audio through firewire or usb devices. Is the 3 prong better than the a/c?

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12th May 2008	#2
skymaster Gear interested Joined: Apr 2006 Posts: 19	Hi Patrick, Using the cord extension rather than the little flip up AC connector just adds a ground connection to the power supply. This is generally a good thing regardless, to drain noise from the switching power supply away. Without it you were probably getting noise on power input which the AlphaTrack didn't like. I have also found that the connections in the flip up connectors get intermittent over time anyhow, or they don't stay securely in wall outlets. I tossed mine and went to the grounded cord a long time ago. Also, some Powerbooks (I think the older/cheaper models) came with a completely non-grounded power supply. Its easy to tell those as the extension cord only has the 2 pins.