Major stuttering causes mentioned here are:
HDD with some bad block: Can be verified with good disk utility tools. It's solved by changing HDD or using an OS that deals better with dying HDD.
Graphics Switching: Can be verified by disabling automatic graphics switching from Intel HD to dedicated graphics. It can be fixed by disabling automatic switching and using only the dedicated graphics card.
Overheating: Can be verified tactile. Fixed using Fan Control, smcFanControl and others.
SSD Usage: May be verified by changing to HDD. Any Fix, Unknown.
It seems in the majority of cases, problems may arise from OS X upgrades. So I think it's recommended when trying to change HDD or SDD, to test a fresh install of Mountain Lion first, to check whether stuttering had gone for good.
Others are trying to get different models involved in this thread which originally targeted the 27" iMacs. A failing hard drive wouldn't cause the audio stutter. At least the symptoms wouldn't be the same. In all my years on a PC I've never seen a failing drive cause that. I have seen bad drivers and firmware do this before in a different manner.
The graphic switching doesn't pertain to the iMacs, but again, is a software glitch. When it is happening on new machines with SSD drives, it seems pretty straight forward. Mountain Goat does run the machine even hotter due to fan throttling and apple allowing the hardware to run hotter in the name of quiet computing. But that in the long haul will have many negative ramifications.
Without over analyzing this, many of these things all happened at the upgrade. Many have said it lessened or was eliminated by reverting back to Lion. If it was bad blocks, then it would not do it on a reinstall or if you partitioned to a different part of the drive. That is because the OS writes files in a different spot. If this was heat related, a cold computer with processor temperatures in the 40C range would not do it, but it does.
The point is this IS software. I'm holding Apple's feet to the fire on this one and have made a fair bit of noise with them thus far. But I'm about to make a lot more noise shortly. I've gotten tired of calling apple and being told their engineering department doesn't know about this issue. They obviously do as they reached out to several of us, myself included. So I'm keeping all my documentation on this and backing everything up as I move forward. I've given them the option of a capture on my systems, requested a refund, and they wish to quote by saying they do not engage in this behavior. Being amicable seems to get you only an apology. But like Apple has done with Samsung, this appears to be increasingly the only language the DO understand. I have two coals left on the fire at this point. Once they are extinguished, I'm sad to say I'll have to resort to plan B.
this is the exact thing. its a software fault, not a hardware fault.
sorry but i can't be that i bought a 2200 Euro system and it stuttering in using youtube which can easily used by a 400 windows notebook ...
i didn't called apple because you did it and there wasn't any result ... maybe if i have time in the next weeks i will call them ... but i think there will be no result ...
so I hope they will look up this thread ... it's mainly a fault on the imac 2011 i guess.
I would highly encourage anyone and everyone that is affected with this issue to contact Apple and continually keep bugging them and ask what is being done about it. To keep bugging them over the issue is seemingly one of the only ways to make them aware. It's obvious they wish to turn a blind eye on this matter, but if the issue is not Going to be fixed, they owe it to customers to make this right in some other fashion.
I don't either. That's why when I escalated to their senior tech department, I told him I'm not going to repurchase Mountain lion in order to do further testing for them. If they want to work around that they need to find some other solution. I have as of yet to hear any kind of solution to that question.
You are wrong.
As I mentioned before, people should not mistake what the issue is about, the issue here is "Sound stuttering after Mountain Lion".
Solutions were presented before for specific systems, and should not be ignored.
This thread is not about iMacs, the OP had an iMac, if it were about iMacs, it should have been explicit in the thread title or section.
I'm here since page 5, before you, and before that page people were already talking about macbooks, retina macbooks, presenting the same problems.
Take notice about the issue please, and anyone that found a cause/solution, don't hesitate explaining and helping.
It's ridiculous how long this issue has affected people and no communication from Apple !!! We don't even know if they are working on this issue !!! I've bought the best iMac (which was my most expensive computer I ever buy) to have something that last et that was powerful. With Montain Lion ("the most advanced operating system in the world" ????) I have now the worst computer I ever own. Even my previous crappy PC did a better job ! I can't even make a movie, listen music or watch youtube without sounds issues and mouse lags.
Even CNET made an article on this issue the 9th AUGUST !!! And we still have no correction and no communication from Apple.
This iMac will be my last Apple product. Even the crappy 300$ netbook I bought 3 years ago is more usefull now than my 3000$ iMac.
sry but, if you understand that it seems ML can't deal better with bad blocks than other OS can, and you indeed checked you have some bad block and that other OS/ partition runs fine while ML don't, you should understand too that your HDD is dying anyway. It will die, even with an OS that has no stuttering because of that.
I agree - it's not just about iMacs. I found this thread by searching for audio dropouts in ML, which were a pretty serious problem for me. So it's about audio. Since I have a new, mid-2012 Macbook Pro, I couldn't run any earlier system than ML, so I couldn't really isolate the problems to the OS version. However, from my experience it seemed that the problem started after the firmware update that accompanied 10.8.2.
As it turns out, a firmware update for my SSD (Crucial M4) seems to have solved the problem. This is a little strange and unexpected, since the new firmware appears to be "fixing" a problem that a previous firmware update from Crucial already fixed on the late-2011 Macbook Pros. Anyway, who knows... But I do still have a feeling that the initial cause of my audio problems was the firmware update that accompanied 10.8.2. More to the point, however, is the fact that it probably isn't any single issue, but rather a mix of issues that's slightly different for each machine. Hence the delay in getting a fix...
I can switch between SL and ML on my 27" iMac.
SL runs flawlessly, ML is all bugged out on the same machine.
It's not only this bug, the more I've used it the more other bugs have come up including the known WiFi bug, iTunes frezzing up, and now quicktime actually stopped working!!! Quicktime??!
I've been mac for decades, never had problems, this Mountain Lion business is junk.
I have to agree about ML. But I also have to add that I think it really started with Lion, and ML just compounded the problems. I have to admit to liking some of the new features, but ML really is a bloody mess. The first thing that needs rethinking is Auto Save. Nice idea, but a bit of a disaster in implementation. As far as all the iOS-style toys are concerned, I don't care either way. They just need to be optimized to ensure they don't mess with the core system (read: audio).
I'm really, really, really hoping that 10.9 is the kind of Snow Leopard of the Lion generation - that is, just as Snow Leopard fixed and optimized everything added in Leopard, <something> Lion will fix and optimize all the stuff added in Lion and ML. Probably wishful thinking, but that's what I'm hoping for.