An unwanted noise maker to watch out for.

Tech talk about audio recording and live stage production.
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An unwanted noise maker to watch out for.

Postby Malcolm Boyce » Wed Oct 08, 2014 5:47 pm

This was a new one for me. Recently mixed a show where some tracks were coming from a Mac laptop. They had been typically using the dreaded headphone out; something that, if I hadn't been clear enough already, isn't the best scenario for the best in audio quality. As soon as we started, there were those typical "computer" noise kinda problems. Just mousing around creating all kinds of wonderful interference. Because I've had similar things happen, I suggested using my USB MobilePre instead as it usually just wakes right up and assumes priority. Identical noises continued, even after we had gone through all the steps of making sure that any monitoring of inputs was off, and anything else we could think of.

Using the MobilePre removed any chance of it being the typical internal generated noise in the analog domain, so I was feeling a little baffled at this point. One of my crew mates (AV nerd Al Richard) comes over and unplugs the power supply from the Macbook and BAM.... Noise gone! OK, so the charging mechanism is somehow causing it to generate noise, all sounding like typical bad "computer" noise. Now, the musician is skeptical, and of course doesn't want to take the chance of running battery only for shows, so it's suggested we try another power supply from another lappy. Totally quiet! I ask the obvious, is the original PS an "Apple" power supply, and lo and behold, it was a knock off generic one. A run to the store and a new "genuine" power supply, and everything is beautiful.

So there you have it... Saving some $ on a cheapo PSU in the long run really cause you some trouble. When they say, "genuine replacement parts only", they mean it. Kinda makes you wonder what the knock off is/isn't doing to the battery and such over the long term.
"Once again, it is NEVER the gear that makes a good record.
It just fills Forum pages..." --compasspnt
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Re: An unwanted noise maker to watch out for.

Postby Jef » Thu Oct 09, 2014 2:03 pm

I've encountered some (Dell) laptops that, if you use a non-OEM power supply, will not pass power on to the battery. Also some of them will reduce the CPU performance if a foreign power supply is detected.
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Re: An unwanted noise maker to watch out for.

Postby Mathieu Benoit » Thu Oct 16, 2014 8:57 am

A proper media player with a line out would have worked too. :twisted:

...But that was an interesting story nonetheless.
"Volume automation takes time. You don't got that kinda time. You could be getting naked with somebody somewhere." -Slipperman

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