how do i disable audio out timeout on a macbook pro causing noise on external amplifier, without having a silent .wav playing in infinite loop?

Question

how do i disable audio out timeout on a macbook pro causing noise on external amplifier, without having a silent .wav playing in infinite loop?

After updating to Mavericks I have this problem. From what I guess, my audio out (either the signal, or the entire soundcard) cuts power after being idle for about 30 seconds. This results in a static noise when connected to my external amplifier. From various forums, dating back to 2007/8 I can see this is not a new problem. The only workaround is playing an empty .wav sound on infinite loop (either by using a terminal command, or by a third-pary app which does this for you), preventing the audio out from timing out and cutting power. This seems to me to be an undisirable proceeding. Even if minimal, it uses extra power and memory. Is there any way to prevent the sound card from timing out like this?

MacBook Pro, iOS 7.0.4, external amplifier

Posted on Dec 9, 2013 9:56 AM

Reply

Answer 1

Best reply

rack0 tack0

Level 4

2,604 points

Dec 9, 2013 11:04 AM in response to marcelvandergrijn

Have you tried these standard cures for ground loops?

http://support.apple.com/kb/HT2743?viewlocale=en_US

Reply

Answer 2

Dec 9, 2013 1:20 PM in response to rack0 tack0

Ok. I tried disconnecting the charger from my macbook and that actually helped. The noise is now so low it is hardly audible, so I guess it has to do with a ground loop. But still, even when hardly audible it still only happens after 30 seconds of idle time. Is that because my theory about a timeout is correct, or is there some other reason for this? This used to just happen when my macbook went on standby (sleep), but now it happens allready after 30 seconds, so even though it may be a loop, it wasn't like this before. I'd love to understand what is different now.

Reply

Answer 3

Dec 9, 2013 1:23 PM in response to marcelvandergrijn

And also: my setup hasn't changed, only the software.

Reply

Answer 4

Dec 9, 2013 1:25 PM in response to marcelvandergrijn

I don't know the answer to your questions but I do know that high gain audio amps are subject to noise pickup.

Balanced lines and differential amplifiers are some ways to help reduce pickup on the cables etc and of course isolation transformers to open circuit ground loops.

It's been too long since I dealt with those things, forgotten most of it.

Reply