buzz if sound out idle
 

i just noticed some strange new behaviour on my macbook: if the sound output is idle for about 30 sec, i get a "plop" followed by a buzz. this is not audible through the internal speakers, but i hardly ever use those. i don't remember ever having had this before updating to 10.4.11

this is really annoying, because to be able to have awaken activating itunes in the morning, i need to keep my amp on during the night (it also serves as a night lamp) but i can't sleep with that buzz. so it's either sleeping or waking up...

It's not audible through the internal speakers because it's not there in the internal speakers. You've got a ground loop.

A ground loop is caused by any number of routes to ground other than one. (If you're in England, or a former English colony, you would phrase that "any number of routes to earth other than one".)

So, you need to make sure that you have exactly one router to ground, and your problem will go away. If you have zero routes to ground, or two routes to ground, you will have this problem.

So, to figure out exactly what is going on, tell us
1. what devices, including your computer and everything attached to it, are grounded. Please list all devices, grounded or not, that are attached to the computer.
2. if the devices are plugged in to the same electrical outlet, or different electrical outlets.
3. If the devices use 3 prong or 2 prong plugs.
4. What country you are in.

Trevor

i'm a sound engineer, i know the difference between a ground loop and my macbook acting strange

but if you really want to know
1. macbook sound output goes into hifi amp, both grounded
2. same outlet
3. euro 230v (shuko)
4. hungary

look, all this has nothing to do with it.
the sound output switches itself off or something and it didn't do that before.

the reason why it's not audible on the internal speakers should also be obvious considering their frequency response an the noise the rest of the computer makes (yes it runs pretty silent from a normal distance but try putting your ear against it).

so once more, for clarity: as long as itunes plays, there is no buzz. if playback is stopped, there's still no buzz.... for about 30 seconds. then there's a pop, followed by a buzz.

sorry i'm a bit jumpy about it, it's just that the 10.4.11 update has been quite a nightmare for me, this problem didn't exist before the update. i finally got my mb working again, i really missed it. i carefully selected a few songs to wake up to, i was looking forward to a good sleep, then the thing starts buzzing on me and it is obviously not a ground loop. unless of course, it's a new kind of viciously self-aware ground loop, the kind that only starts looping after 30 seconds of inactivity on the line, just to be even more annoying.

anyway, i think i found a (partial) explanation: i usually have the power adapter connected during the night. just now i was running on battery. i tried connecting the adapter when the buzz was already there and that didn't make a difference. in other words: i stopped playback while on battery power, a bit later the buzz came, then i connected to mains power. however, if i stop playback when the adapter is connected i don't get the buzz.
so it must be something switching off to save energy.

still, that doesn't explain why it didn't happen before. i've often used the sound out on battery power as well, i paid a lot of money for a set of headphones that are so comfortable that i sometimes forget to take them of even if i'm not sending out any sound anymore and i don't remember ever getting that buzz.

What do you have set in System Preferences > Energy Saver > Options tab?

Trevor

battery: all 3 options are checked

power adapter: all 4 options are checked

I have the same issue on my MacBook Pro, first-gen. I believe it's related to halting or diminishing power to the port when audio ceases, but that's partially a guess.

You didn't mention what you have "Processor Performance" set at. Perhaps try setting that to "Highest" and see if the behavior changes.

Trevor

erm, i don't see the "processor performance" option. is that supposed to be in energy saver -> options?

Maybe the MacBook doesn't have that option. I can change Processor Performance on my PowerBook G4, but the options in Energy Saver are hardware-specific, so this setting might be unavailable to you.

I've attached a screenshot of my Energy Saver > Options tab for your information.

Trevor

Hello,
I have the exactly same problem with the Mac Book I bought last month!
Any hint?
Thanks,
FX

Do you use the extension cord (grounded) or the 2 prong adapter (ungrounded) on the power supply?

The processor adjustment in the Energy Saver is not available on Intel Macs.

I have the buzz on sound idle wether i'm on battery, power with extension cord or 2 prong adapter.

Is this the kinda problem where I should call Apple Care?

Sure. If you're covered, that's what they are there for.

Trevor

They couldn't do anything for me. They kinda said that since I use external device (my amp+speakers), it's none of their business.
Anyway, it seems that the problem comes from au auto-shutdown of the soundcard, since the buzz I hear is the same as if my jack was not connected. This is not a problem if you use headphone because it doesn't amplify the signal but if yo amplify a not grounded signal, it gives this ugly buzz I hear after 30sec of no sound activity.

Has anyone heard of this auto-soundcard-shutdown? Is there anyway to configure and/or disable this function?

Thanks for your replies,
fx

Buzz
 

Macbook, Intel, Leopard.
Running on battery power, using Sound Studio to record music from vinyl records. MacBook goes to sleep, Sound Studio continues to record.

Affer I wake up the MacBook I get a two-part noise. First a series of clicks for three seconds, then two seconds of silence, then four seconds of variable buzz.

I have not seen the buzz while the Mac is asleep, only after I wake it up.

Power save options for battery are default settings:

computer to sleep when inactive for 12 mins;
display to sleep when inactive for 4 mins;
Options selected to slightly dim when on battery power,
automatically reduce brightness of display before display sleep, and
show battery status in the menu bar.

I don't want to disable power saving. Can I get rid of the buzz by adjusting these settings?

Thanks.

Harvey

I have an identical problem to the original poster. It comes from the power supply or battery charger. When I disconnect the power from the wall, there's no more buzz.

Running WinXP on the MBP also gives a buzzing sound until it's logged in and the sound drivers activated, at which stage the buzzing stops.

You probably have a "ground loop", in other words more than one route to ground. What peripherals do you have exactly? Tell us, in detail, everything that is plugged in to the MacBook Pro, especially including any external speakers and how they are connected and powered.

That's very odd. You're running Windows using Boot Camp?

Trevor