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-   -   Macbook Pro Owners- Asio spikes (https://www.gearslutz.com/board/music-computers/646013-macbook-pro-owners-asio-spikes.html)

Ivorydom 6th September 2011 06:13 PM

Macbook Pro Owners- Asio spikes
 
Hello everyone,

I am running Cubase 6 on a Macbook Pro 2011 with 2.2 i7 CPU, 8gb ram and 7200 rpm hard drive.

Cubase 6 32 bit, OSX 10.6.8.

What I am trying to do is playback a single stereo file, with no FX or VSTi's in Cubase. Whenever I do that, although the Asio meter is very low (2-3%) I get asio spikes and clicks all the time. I use the internal soundcard of the Macbook Pro. Buffer size is 256.

Is this normal? I would expect the internal soundcard of Macbook Pro to be more than capable of running a single stereo file in Cubase without CPU spikes.

I have tried disabling Airport, bluetooth and running Cubase in 64bit mode. The problem still exists.

Any macheads here know what I should do? Is this a normal behavior?

Thank you!

HughH 6th September 2011 06:32 PM

Hello,
The internal soundcard on a MBP can deal with many, many tracks of playback - I regularly use it on airline flights to do content cuts with 128 tracks of playback plus the other tracks.

I suspect your card buffer settings may be too low. If you're mixing try upping them to 1024 samples, that should give you plenty of breathing room.

Also, and this isn't directly related to your issue but can cause infrequent problems that are hard to trace - be sure to do the usual Mac optimizations to be sure the OS isn't going off on it's own when you don't want it to.

Hugh

Ivorydom 6th September 2011 07:13 PM

Thank you for the reply,

Well, this is weird, when I set the buffer to 128 the problem stops. If I set it higher to 512, problem stops. It only happens in 256 buffers.

Goosebumps?

kilon 6th September 2011 07:28 PM

there is no asio in macs
Everything is handled by core audio, which is macos native sound api.

Most likely it smells like a bug to me of your Cubase which has a notorious reputation amongst macos user as a large pile of crapola. Mainly because of its arsenal of bugs in the macos version. Not that windows version is ideal.

My advice to you is forget cubase on mac and save yourself the frustration , by going either logic , ableton live or digital performer route. I have only demoed some Cubase version on my imac and it was a joke for a mac app, experienced several crashes with it, which definetly something that as a mac user I dont accept as easy I was accepting it when I was using the Cubase windows version.

I can bet serious money that your problems have nothing to do with your Audio card or macos. And that is east to confirm , by trying other DAWs , if the problem does not appear then its clearly a Cubase issue.

Ivorydom 6th September 2011 07:51 PM

Quote:

Originally Posted by kilon (Post 7005216)
there is no asio in macs
Everything is handled by core audio, which is macos native sound api.

Most likely it smells like a bug to me of your Cubase which has a notorious reputation amongst macos user as a large pile of crapola. Mainly because of its arsenal of bugs in the macos version. Not that windows version is ideal.

My advice to you is forget cubase on mac and save yourself the frustration , by going either logic , ableton live or digital performer route. I have only demoed some Cubase version on my imac and it was a joke for a mac app, experienced several crashes with it, which definetly something that as a mac user I dont accept as easy I was accepting it when I was using the Cubase windows version.

I can bet serious money that your problems have nothing to do with your Audio card or macos. And that is east to confirm , by trying other DAWs , if the problem does not appear then its clearly a Cubase issue.

When I said about Asio I meant the Asio meter in Cubase. I know about the core audio.

It seems to me more like a bug with the Core Audio driver rather than Cubase. And let me explain: if I run Cubase on my MacBook with my RME UFX or my TC Impact Twin everything runs smoothly. So the problem only occurs with the onboard audio.
Cubase runs very well here with my audio interfaces.
I will definitely not change my sequencer because of spikes with the internal MBP soundcard.
I would really look forward for feedback from Cubase users though. Thanks.

Robosapien 6th September 2011 07:59 PM

I had an issue not so long ago with Intel graphics drivers, I uninstalled them - not an ideal solution but now works. a bit ghetto though. This was affecting everything not just core audio though, and regardless of buffer size. I doubt this will help you but just thought I'd add my tuppence.

Ivorydom 6th September 2011 08:05 PM

Quote:

Originally Posted by Robosapien (Post 7005314)
I had an issue not so long ago with Intel graphics drivers, I uninstalled them - not an ideal solution but now works. a bit ghetto though. This was affecting everything not just core audio though, and regardless of buffer size. I doubt this will help you but just thought I'd add my tuppence.

Thank you.
No, here all works well with external audio interfaces. It seems to be a problem with the built in audio.

kilon 6th September 2011 08:17 PM

Quote:

Originally Posted by Ivorydom (Post 7005292)
When I said about Asio I meant the Asio meter in Cubase. I know about the core audio.

It seems to me more like a bug with the Core Audio driver rather than Cubase. And let me explain: if I run Cubase on my MacBook with my RME UFX or my TC Impact Twin everything runs smoothly. So the problem only occurs with the onboard audio.
Cubase runs very well here with my audio interfaces.
I will definitely not change my sequencer because of spikes with the internal MBP soundcard.
I would really look forward for feedback from Cubase users though. Thanks.

Used Cubase for 3 years on windows, can I speak now ?
gooofheh

not that cubase users can do anything to help with your problem. I can even bet you that its CPU spikes and not core audio bug, the problem appeared in some of the versions of Digital Performer too , it was a known problem did not matter if you used an audio card or internal audio, I used an audio card with it and it was purely a DP bug.

EDIT:
Oh it seems I won the bet ---> www.steinberg.net • View topic - [MAC] CPU Spikes (MR816)

and there are other threads too. Actually the net is littered with Cubase macos problems, it must be one the most problematic DAW on macos. As I said a large pile of crapola diddlydoo

Of course if you want to continue using it dont let me stop you one tiny bit . Its a free world afterall.

valis 6th September 2011 08:25 PM

It's possibly related to using not enough cpu power, cpu spiking at low loads is typical of post-nehelem era core flushing issues.

Ivorydom 6th September 2011 09:31 PM

Quote:

Originally Posted by kilon (Post 7005385)
Used Cubase for 3 years on windows, can I speak now ?
gooofheh

not that cubase users can do anything to help with your problem. I can even bet you that its CPU spikes and not core audio bug, the problem appeared in some of the versions of Digital Performer too , it was a known problem did not matter if you used an audio card or internal audio, I used an audio card with it and it was purely a DP bug.

EDIT:
Oh it seems I won the bet ---> www.steinberg.net • View topic - [MAC] CPU Spikes (MR816)

and there are other threads too. Actually the net is littered with Cubase macos problems, it must be one the most problematic DAW on macos. As I said a large pile of crapola diddlydoo

Of course if you want to continue using it dont let me stop you one tiny bit . Its a free world afterall.

Ok, Cubase user from Cubase 24/32 here.
First of all the link you provided shows that the problem was due to the audio interface driver.
Secondly, how do you explain that Cubase runs smoothly with any external audio interface except for the internal audio? Please elaborate.

valis 7th September 2011 12:04 AM

External audio interfaces may put your cpu into a different state. There's a well researched thread here for instance that shows interfaces that use the default Apple firewire driver will prevent core sleeping (and generate more heat for those that don't want it, but it does prevent audio dropouts.)

Yutaka 7th September 2011 12:36 AM

I think there is a "Steinberg Audio Power scheme" setting that prevents the processors from going into energy saving state in "Devices -> VST Audio system". I've recently moved to PC and don't know if that exists in mac version, but if there is, you may want to try that.

Ivorydom 7th September 2011 12:47 AM

I believe this power scheme is an option available only in Windows but I don't have Cubase available right now to check.
Still the problem only happens in 256 samples, not higher and not lower. 128 samples work like a charm!

kilon 7th September 2011 08:08 AM

Quote:

Originally Posted by Ivorydom (Post 7005580)
Ok, Cubase user from Cubase 24/32 here.
First of all the link you provided shows that the problem was due to the audio interface driver.
Secondly, how do you explain that Cubase runs smoothly with any external audio interface except for the internal audio? Please elaborate.

Besides being a computer user for over 23 years now. I also happen to be a programmer for 23 years now, not a pro but a guy that has played around pretty much all significants programming languages out there.

I posted the above link to prove that is a Cubase issue. The thread mentiones it as a driver problem too, but you have to understand one thing though , if it is a driver problem however it happens only with Cubase as the thread seems to imply. Then its a cubase problem, if it happens with all DAWs or some of them then its still a Cubase problem.

Programming is a complicated job, bug will always exist. Sure every audio interface company has the obligation to make sure that the drivers work well and perform well with every OS and every available DAW.

BUT the computer is a highly complicated machine, a user assumes that if the driver has a problem, then that problem will appear with all DAWs. Howeveve thats is rarely the cases , sometimes problems do not even appear each time you do the same thing, they just seem to appear and disappear when they seem fit. Why? because inside an OS there are like a gazillion ways that something may go wrong.

So its common practice among developer to do what we call "tests" you may be aware for example of "beta tests" or even "Alpha tests" those are test that users participate but of course before them there are many more done by the developers themselves. The bottom line is that a programm that is not tested to the bone , is crap in my book.

DAWs SHOULD BE TESTED AGAINST ALL CURRENT AUDIO INTERFACES BEFORE GETTING RELEASED!!!



Cubase is notorious for its bugs in macos because the company probably does not employ enough programmers to perform these tests and because they simply dont care. In this link it proves 3 extremely important points.

1) Steinberg did not bother to test their own audio interface product drivers

2) Steinberg did not bother to test Cubase with these drivers

If you are asking me if I am sure that your problem is not with bulit in driver, my answer is no. Afterall that is why i said I am willing to bet that is not , I never said I know that I KNOW it is not, and I am willing to take this bet which I may or may not lose because I know and have researched and talk to people that experienced a gazillion problems with cubase on macos specifically. Its a buggy software , by buggy I mean alot of bugs that should not even be there. And you have a extremely buggy software in front of you it will be your first suspect to any kind of problem.

What I did say to you however is to perform this simple test , test your bult in audio with other DAWs if other DAWS perform those CPU spikes then yes its mostly a built in audio issue, if they do not then no its most likely not a built in audio issue.

Of course all this is theoretical , true solution of bug is through a debugger that executes line by link step by step , freezing each step for the developer can jump in and see exactly what the software does either the DAW or the driver or both. And since you are not a developer and I do not have access to Cubase or MACOS source , your best bet is to contact both Steinberg and Apple , since those too will be the only ones that can perform the debuging.

Why the problem appears with your built in audio and not your other audio interface if its not a built driver problem ? Take my word I can show you far far stranger bugs than this. Bugs were , are and forever will be a huge pain in the ass for any developer exactly because they can be extemely hard to predict and to diagnose and that happens because even the best developers out there dont know exactly how computers work and perform under diffirent circumstances as the technology has become extremely complicated.

The only thing you can do is do the above tests i suggested and report the problem directly to the companies.

Oh I almost forgot to add that I assumed its not a built driver problem too because I happen to own a macbook air with snow leopard and its audio interface performs very smoothly and I am sure that million of users out there will already have reported such a big problem, but you never know, maybe its not a driver problem or a DAW problem and you happen to own a faulty builty audio card.

Ivorydom 7th September 2011 09:32 AM

Quote:

Originally Posted by kilon (Post 7007176)

Oh I almost forgot to add that I assumed its not a built driver problem too because I happen to own a macbook air with snow leopard and its audio interface performs very smoothly and I am sure that million of users out there will already have reported such a big problem, but you never know, maybe its not a driver problem or a DAW problem and you happen to own a faulty builty audio card.

Well, first of all thanks for even taking the time to write all this. I see what you're saying. I am not arguing about the fact that a bug could be as complicated as it can get. I have been a beta tester for highly respected companies in the past and I have even helped audio interface companies solving bugs with their drivers using beta versions of their drivers as well.

I also understand that this problem may be specific to Cubase, this is very possible. Not arguing on that either.

The only thing I argue is the fact that since you have good knowledge of programming, you are aware that there is NO program out there that is free of bugs. If you make a search in this forum you will find posts with people exposing bugs of Logic. So guess what: Apple owns Logic, owns their OS and owns their hardware. What a perfect combination-STILL! there are bugs. Unacceptable? Well, according to me yes, but this is how software works I am afraid.
I don't know if you are still a Cubase user(I guess not) but version 6 was the most stable x.0 version of software I have ever tried and many users are saying that. Maybe you have bitter memories with Cubase or just prefer logic but the way you write about it is very dogmatic. This is what I am arguing with. I use Cubase both with Windows and OSX and I do very complicated stuff with it , I am not using it as a tape recorder but really pushing it to the edge(composing film music, very heavy VSTi's such as PLAY, Omnisphere, Vienna Symphonic library). So believe me , if there are bugs I am the first to want them solved. But really I don't see all the "crapola" you are talking about or the "notorious" reputation of Cubase you mention. You may not like Cubase or did not work for you, but do you think it is sensible to suggest a change of DAW because Cubase even has a bug with the Mac onboard audio? This is the only part that does not make sense. If you read my later posts the problem only appears on 256 samples. Works fine at 128 or all the other buffer sizes which is weird but even better :-p (yup, computers are complicated animals ;-) )

Anyway if you have any ideas I would be happy to hear them but this is such a small issue that I won't lose sleep over it. As strange as it seems to you, Cubase works very well here both in W7 and OSX. I really wonder what kind of huge problems you had while using Cubase but maybe this is not the right thread to continue on that basis.
Also, when I asked feedback from Cubase users, I did not mean to underestimate your post or opinion. But if someone has a MacBook pro, with Cubase it is likely that he will have that problem. If not, there's something wrong with my system so I would have to look elsewhere for the cause. Fortunately, MacBooks have fixed hardware so pinpointing simple problems like this is easier.

Timur Born 7th September 2011 12:05 PM

I just finished an installation Marathon here, but will install Cubase on OS X once I find time and look into this. Valis' suspicion seems the most likely to me and there are some ways to validate them. I'll report back once I'm done.

kilon 7th September 2011 12:36 PM

Quote:

Originally Posted by Ivorydom (Post 7007323)
Well, first of all thanks for even taking the time to write all this. I see what you're saying. I am not arguing about the fact that a bug could be as complicated as it can get. I have been a beta tester for highly respected companies in the past and I have even helped audio interface companies solving bugs with their drivers using beta versions of their drivers as well.

Thats great to know you appreciate what a menace a bug can be and you help developer eliminate them.

Quote:

I also understand that this problem may be specific to Cubase, this is very possible. Not arguing on that either.
I thought you did. Maybe I misunderstood.

Quote:

The only thing I argue is the fact that since you have good knowledge of programming, you are aware that there is NO program out there that is free of bugs.
Absolutely

Quote:

Unacceptable? Well, according to me yes, but this is how software works I am afraid.
its not unacceptable if those bugs are rather specific and very hard to find. I never talked about a bug free software I talked about a software that at least has passed some basic and abit more advanced tests. That one is certainly unacceptable for every self respecting user and developer .

Quote:

I don't know if you are still a Cubase user(I guess not) but version 6 was the most stable x.0 version of software I have ever tried and many users are saying that. Maybe you have bitter memories with Cubase or just prefer logic but the way you write about it is very dogmatic.
No I am no longer a Cubase user last time I used it regularly was in 2000 . No I dont have bitter memories in terms of bugs actually back then was very stable, I just never clicked with the interface. My bitter memories was with a demo I tried on macos. Experienced several severe crashes , which made me angry and then talked to some friends of mine using a mac and visited some forums to find out that there was a tsunami of complains about cubase bugs on macos and the software seemed like in a very bad state.

Quote:

This is what I am arguing with. I use Cubase both with Windows and OSX and I do very complicated stuff with it , I am not using it as a tape recorder but really pushing it to the edge(composing film music, very heavy VSTi's such as PLAY, Omnisphere, Vienna Symphonic library). So believe me , if there are bugs I am the first to want them solved. But really I don't see all the "crapola" you are talking about or the "notorious" reputation of Cubase you mention. You may not like Cubase or did not work for you, but do you think it is sensible to suggest a change of DAW because Cubase even has a bug with the Mac onboard audio? This is the only part that does not make sense. If you read my later posts the problem only appears on 256 samples. Works fine at 128 or all the other buffer sizes which is weird but even better :-p (yup, computers are complicated animals ;-) )

Anyway if you have any ideas I would be happy to hear them but this is such a small issue that I won't lose sleep over it. As strange as it seems to you, Cubase works very well here both in W7 and OSX. I really wonder what kind of huge problems you had while using Cubase but maybe this is not the right thread to continue on that basis.
Also, when I asked feedback from Cubase users, I did not mean to underestimate your post or opinion. But if someone has a MacBook pro, with Cubase it is likely that he will have that problem. If not, there's something wrong with my system so I would have to look elsewhere for the cause. Fortunately, MacBooks have fixed hardware so pinpointing simple problems like this is easier.

To be sincere I thought you were not an experienced user and you just started with Cubase, but if you say its stable on the mac then its stable o macos.

I tried 2 years ago maybe they made it stable ever since I dont know, you motivate me to give it another try. Whether you should search the cause of your problem is up to you. If I was you I probably would not waste my time on something that does not really bother me. Anyway me saying Cubase is abig pile of crapola, had to do only with me demoing it 2 years ago.

I am an ableton live user, and I dont like Logic's interface either, though I prefer it from Cubase. Other than that, dont get too annoyed with my "large pile of crapola" it target the software not you, or the developers, I believe even with bad software one can make extremely good music. So carry on using Cubase will all means and if it is now rock stable so much the better I won complain anymore and even praise it if its really good.

Ivorydom 7th September 2011 01:44 PM

Quote:

Originally Posted by kilon (Post 7007659)

To be sincere I thought you were not an experienced user and you just started with Cubase, but if you say its stable on the mac then its stable o macos.

I tried 2 years ago maybe they made it stable ever since I dont know, you motivate me to give it another try. Whether you should search the cause of your problem is up to you. If I was you I probably would not waste my time on something that does not really bother me. Anyway me saying Cubase is abig pile of crapola, had to do only with me demoing it 2 years ago.

I am an ableton live user, and I dont like Logic's interface either, though I prefer it from Cubase. Other than that, dont get too annoyed with my "large pile of crapola" it target the software not you, or the developers, I believe even with bad software one can make extremely good music. So carry on using Cubase will all means and if it is now rock stable so much the better I won complain anymore and even praise it if its really good.

Now I get it. Fair enough, an inexperienced user may be at a point where he can switch easily ( by the way inexperienced user with an RME UFX kind of overkill isn't it? Hahaha).
I have been using all major DAWS from time to time (ProTools, Logic, Sequoia) because I have been working as an arranger or sound engineer in recording studios. In my studio I use Cubase. I did not get offended on Steinberg's behalf if this is what it seemed.
If you like Ableton then in my opinion you don't even need to try Cubase. But if you do, you will see that there is a HUGE difference from 2000 and the feature set is insane right now (although still no sampler *moan*).

Anyway thanks for your input and happy music making!

Ivorydom 7th September 2011 01:44 PM

Quote:

Originally Posted by Timur (Post 7007611)
I just finished an installation Marathon here, but will install Cubase on OS X once I find time and look into this. Valis' suspicion seems the most likely to me and there are some ways to validate them. I'll report back once I'm done.

Thank you Timur, this would be great!

Timur Born 13th September 2011 07:11 PM

Soooo.... The whole thing is a bit complicated and likely a mixture of several things coming together. Unfortunately there are no sophisticated and reliable measuring tools available for OS X (that I know of) other than a half-baked CPU state monitor called MSR Tools. So everything said here is to be taken with a grain of salt.

OS X Core Audio + CPU power-states

OS X - just like Windows - usually tries to keep the CPU frequency as low as possible, but in contrast to Windows (power-profiles) you get absolutely no control over the performance vs. power-saving balance.

When the internal audio-interface is used it seems that using lower sample-buffers leads to the CPU being *less* often/aggressively clocked down, while larger buffers allow more clocking down. A turning point seems to be around 200 samples buffer.

When external audio-interfaces are used (FW or USB, likely ExpressCard, too) then *no* clocking down. Furthermore none of the CPU cores seem to be parked in lower sleep states (C3/6/7) anymore, which also turns off Core Parking (the latter likely not being the culprit discussed in this thread).

Cubase vs. Audio buffer vs. CPU load vs. "Switching"

Cubase starts with a relatively high CPU load even with nothing loaded and playback being stopped, just the engine running. On the plus side this seems to keep the CPU in a state similar to what I described for external audio interfaces. While this leads to higher CPU temps it helps audio performance (I played back 128 duplicated stereo tracks at 32 samples on 1 single CPU core).

Unfortunately whatever Cubase does is not consistent. You *do* get massive dropouts at 256 samples, but not always. Even worse, switching around a lot can lead to 256 samples working perfectly well, while 128 samples causes troubles. Usually the culprit is 256 samples though.

Very likely it is 256 samples because that so close to the "turning point" I described above. The CPU is frequently clocked down (=higher load for the now slower CPU) while the sample buffer is not big enough yet to deal with all higher load and constant switching.

This is not a "constant" problem though. Starting Cubase with 256 samples already set from the last session allows flawless playback here, but only as long as the sample buffer is not being switched back and forth to another value.

But even when playback starts to massively drop out at 256 samples there are ways to stop the drop-outs. 1) Turn off the audio inputs! 2) Create a low CPU load (i.e. Coolbook's CPU Load slider at 1 or 2 out of 10).

Switching around with inputs, outputs, load and buffers may even lead to 256 samples being usable again with put inputs and outputs enabled and no "third-party" CPU load created. But that's rather erratic.

Ableton Live does not suffer from this "turning point" and the way Cubase behaves to different starting/switching situations suggests that it is more an issue of Cubase than of CoreAudio. On the other hand Live performed *very* bad on first generation i7 OS X Macs, so the whole thing likely is CPU specific, too.

Timur Born 16th September 2011 10:54 AM

I'll file a report to Steinberg once I find time and also test some other interfaces' behavior.

Ivorydom 16th September 2011 11:02 AM

Quote:

Originally Posted by Timur (Post 7037284)
I'll file a report to Steinberg once I find time and also test some other interfaces' behavior.

Hello Timur and thanks for reporting,

Something interesting that I have found out is that the problematic buffer seems to be the one you boot your MacBook with. I noticed for example that if I boot my MacBook with a buffer of 192 samples, then Cubase crackles with this buffer size and changing to 256 fixes the spikes! Also I noticed that if I go to the audio setup of my MacBook and change the bit rate from 32bit to 24bit while Cubase is still running spikes stop as well.

It is weird but it happens. Still, with my audio interfaces I get no spikes whatsoever.

jaymo99 28th March 2012 09:42 PM

Think i found an answer
 
Hi , Im jaymo new here and was drawn here because i was having the same ASIO spike in Cubase 6 issue as some of you... while bring everything in my power to track this down and having no luck i finally found this on the AVID site for pro tool . its an optimisation guild heres the link

Mac Guide - Mac OS X 10.7 Lion Optimizations and Troubleshooting

So i did all that they suggested and things did get slightly better but still had the spike when recording more then i could deal with ( frankly i think it shouldn't be there but it is so must be delt with anyway...)
But i did notice one thing when i had a track expanded and it scrolled to another page i almost always got a spike... so i got to thinking maybe this is somehow graphic related.. i mean it made sense because im only running 13" macbook pro i7 with 8 gb ram and 500 gb hybrid drive and it has the Intel HD 3000 graphic chip so it shares a portion of ram...

So what i did was uncheck everything in the transport window and removed the wave forms in the audio tracks and way la... not a single spike not one and I've been testing it for the last 4 hours ..recording over the save audio bits multiple times and its works flawless only draw back is no transport window & no wave lines when recording but i can live with that for now as i have a faderport playback hasn't been a problem only really recording

so yea works for me maybe it helps someone

again what i did was
  1. followed the recomendations here by avid Mac Guide - Mac OS X 10.7 Lion Optimizations and Troubleshooting
  2. Turned off everything in the transport ( right click or alt click uncheck everything) then goto transport in the menu bar and uncheck that
  3. then goto the menu bar and click on Cubase>Preferences>event display>audio and uncheck show waveforms

Hope this helps

My studio
Macbook pro 13" early 2011 i7 2.8/ 8gb ram/ 500GB hybrid OS drive/ 3TB seagate usb drive/ Motu Ultralite Firewire 2G/ Presounus faderport/Cubase 6.0.6/Waves V9/EZ Drummer/EZ MIX/ Amplitube 3/MarkBass plug in/a bunch of NI stuff

:)

Timur Born 8th April 2012 10:18 AM

I lately discovered some general audio performance issues of OS X Lion vs. Snow Leopard. These affects a number of audio applications on different levels. Cubase, for example, might show a maximum CPU load of around 50% via its own meter (F12), but see the red overload LED turn on sporadically (may be connected to external plugins).

Ableton Live shows some rather strange behavior of producing dropouts with an audible frequency depending on the currently set audio buffer size (lower buffer = higher frequency), but turning the audio engine off->on fixes it until you change buffer sizes again.

It's all not very clear yet, so I need more time to investigate.