Crackle sound from speakers on boot

[revlimiter]

When I boot into Yosemite I hear a fairly loud crackle sound from my speakers. After that the sound seems to work fine. Is there any known issue with this, and also any way to fix it?

Thanks,

 

[toleda]

hear a fairly loud crackle sound from my speakers.,

See toleda/audio_ALC_guides/Capabilities - Realtek ALC AppleHDA_v2 [Guide].pdf/Audio Popping Solution

 

[UtterDisbelief]

See toleda/audio_ALC_guides/Capabilities - Realtek ALC AppleHDA_v2 [Guide].pdf/Audio Popping Solution

I have read around this problem, which isn't new, and Toledo's guide notes, but don't seem to be finding any real explanations.

Does anyone actually know what a MacPro 3,1 definition does that a.n.other does not?

I've run with 3,1 for years but, taking on board other things like iMessage problems, felt it was time to explore alternatives. The iMac 14,1 certainly helps my Hack' work smoother and I've noticed real improvements in graphics scrolling (for example). It seems to match my hardware better.

Is it a power-management issue? I understand that the system powers-down the sound circuits if they aren't used and that the pop occurs when it is brought back up again. But it doesn't happen in 3,1. As my system hardware and drivers do not change - just the definition - I'm guessing there's something OS X does in response to the change which causes a "pop". Given that the sound drivers work in either definition does the underlying O/S ramp up the voltages more slowly for older defs avoiding capacitor power leaks?

Must be some, real cause.