I am running a Macbook Pro 15" into an edirol USB interface which connects to my Samson Rubicon R6a monitors via XLR. My power supply causes horrible noise in my monitors and i am aware i need to buy an isolation transformer. Anyone have any recommendations? My budget is about £50 maximum.


I work on live events. i have a macbook pro and i use a usb interface (apogee one) for walk up music cues, and a di box with an earth lift switch (interspace industries pc di box about £65) out of the headphone socket for another output like background music(any di box with an earth lift will do) with the earth lift switch on, that gets rid of the power supply noise across both. Regarding noise from the internal workings of the laptop I always have the laptop volume at full. The lower you have the volume on your MBP the closer you are to the machines noise floor. Hope that helps.


You can't cheap out if you're planning to use transformers. The cheaper they are, the more likely they are to mangle and distort your audio...something you don't want happening in your monitoring chain. You need to be able to trust what you're hearing. Good transformers are expensive. Jensen are some of the highest quality you can buy, but they aren't cheap either; you get what you pay for.

If you can't afford the entry cost for quality transformers, you're better off looking for a different solution. Where are all of your cables positioned? There may be a simple solution if you give that some careful consideration.


Regardless of the source of the interference (dirty mains power, the power supply, a faulty component, or something in the laptop), there is a strong link between the audio interface and the interference that ends up in the audio path. If the manufacturer cut corners in the shielding of the audio components, EMI-noise ends up in the audible range.

I've had an Edirol interface years ago, and I sold it because I could hear hard-disk activity, screen redraws and processor activity through the audio outputs. This noise became a lot quieter when I disconnected the power supply from my laptop, but it was still there if I turned up the volume.

Other interfaces did not have this problem.

A transformer might help, but try to borrow one to see if it actually improves things, and while you're borrowing, also try out a decent audio interface to check what that can do for you.

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