First steps to take:
Turn off any networking adapters. Increase the buffer sample size. Don't move the mouse at all when tracking if you can help it. Make sure all digital cables are connected and tight-sometimes the pins can get corroded so it's not a bad idea to pull the cable off and push it back on.

Now if none of the above works then you have to go step by step. Start at your interface. Unplug all inputs and record some tracks without connections. Do you still get the crackle? If so then it's in your interface or more likely the computer. Embedded video chips on motherboards are culprits for this type of thing as well as extraneous USB connections and unnecessary mouse movements.

If the interface/computer combo doesn't produce the crackle then connect one piece of gear and try again. Crackle? Swap the cables. Crackle? Continue adding gear until the crackle occurs or you have sussed it all out.

i've heard that sound before.
i use to run two aardvark q-10 interfaces and the clocks would drop out of sync once in awhile and i would hear exactly the same thing on playback.(didn't hear it during recording).
could be a clock related problem.
i don't know but maybe threre's a clue there.

That's not the crackle I'm used to via network adapters. Are you doing a lot of processing (multitracking) while recording? Network adapter, or cable across interfering sources has more of a click than the crunch that that seems to be. You might use a resource monitor and see if there's any peaks in resource usage that coincide with the crackle. Any usb/firewire interface while also using usb/firewire HDD to store the data? Could be a lot of things. My guess would be a resource bottleneck. But it could be a lot of things. Power issues? Filesystem commit interval? and tons of other potential candidates. Some of which depends on how consistent / regular the issue is, or how random.

First, my rant... why is happening to me? Does every other Mac user (or PC user) deal with this kind of thing or is this payback for some sort of bad karma? I thought this stuff should be plug-and-play! Okay, I'm done. Thanks for your patience!

Thanks to each of you for priming the pump with some good ideas. It seems to be a good list of potential issues. I'm guessing the answer is going to be in there. That said, there are so many possibilities! Yikes! The good news is that I have a list that can help direct my next steps - whatever they may be. They have also sparked new thoughts and history I can share. Maybe the list can be narrowed somewhat!

Here’s a bit more history. This issue first showed up when I was using a different setup. I had a small board connected to the computer via USB. At the time, I was reading on forum posts that Apple had something funky going on with their USB connection. So, I purchased my current preamp and connected up using an optical cable. It appeared the problem was solved - but no.

Given that this has happened with two different preamp setups (connected by two different wiring types), I think I can rule out wires and external HW. That leaves a potential HW or SW issue with the Mac, an interface issue (I’m thinking the clock issue fits in here), some sort of incompatible software settings, or a seemingly random intrusion by something like Airport or an electrical surge.

Regarding the potential clock issue, is there any way to confirm this without purchasing a new piece of equipment. Is there any way to force the clocks to go out of sync just so that I can hear the effect? I have (what I thought was) a relatively simple setup - just my computer and a Art Digital MPA connected with an optical cable. Am I understanding that it doesn’t matter how simple it is - connect one piece of outboard hardware and the potential for clock issues exists?

I'm going to try to focus on some of the easier things to test so that I can narrow the list. In the mean time, I'd like to hear your thoughts about my observations above.

Thanks again!

How many tracks? What's the specs of the PC? What OS / version of OS? How much RAM? A lot of software issues can be solved by doubling your RAM. Strange but true... Not really solved, but a lot less frequent. You could try an alternative OS (linux) and see if that cures your issues, therefor confirming software related, and not hardware per say. Lots of ways to troubleshoot. But until you rule this and that out, you still DON'T KNOW anything for certain.

I'm recording one track at a time. I am simultaneously playing a scratch track (instead of a click). And, my memory is maxed out.

Here's my gear profile:
Cubase Studio 5
Art Digital MPA Preamp
AudioTechnica 3035
Oktava MK-012
AKG C1000
Adam-A7 Monitors
Velodyne sub-woofer
MacBook Pro
Model Identifier: MacBookPro3,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.4 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 4 GB
Bus Speed: 800 MHz

RAM looks good, CPU good. You can probably rule out the interface and connection cable.

Is it just the one mic? Or every mic?

How many tracks are involved with your scratch track? 1, 2, 8+? Any special effects in place, reverb, distortion, ???

How many tracks total in the project? How long are the tracks in the project?

I'd start with trying other mics, if the same effect is happening on multiple mics, then it's probably not the mics. Making it probably computer / power supply / software related. Try recording with audacity and see if the mic(s) have the same issue. Put a PSU between the computer and the wall to stabilize power and rule that out. It could still be anything. It might not even be in your house, radio station? power sub-station? neighbor is a HAM radio enthusiast? Other neighbor is a CB maniac with a beefy system in their house? neighbor is a first responder (fire / police / ambulance)? Depending on how frequent the issue is. Neighbor has a microwave based internet connection? Neighbor is a cell tower? Could be lots of things.

There is no way that machine is maxed out-at least if it's operating system is a clean install.

The other problem I see immediately from your gear list is that you do not have an audio interface. The ART Digital MPA is designed to send the audio into an audio interface prior to it being seen by the computer. This would also give you the ability to direct monitor latency free.

bassberry, post: 344437 wrote: First, my rant... why is happening to me? Does every other Mac user (or PC user) deal with this kind of thing or is this payback for some sort of bad karma? I thought this stuff should be plug-and-play! Okay, I'm done. Thanks for your patience!

Thanks to each of you for priming the pump with some good ideas. It seems to be a good list of potential issues. I'm guessing the answer is going to be in there. That said, there are so many possibilities! Yikes! The good news is that I have a list that can help direct my next steps - whatever they may be. They have also sparked new thoughts and history I can share. Maybe the list can be narrowed somewhat!

Here’s a bit more history. This issue first showed up when I was using a different setup. I had a small board connected to the computer via USB. At the time, I was reading on forum posts that Apple had something funky going on with their USB connection. So, I purchased my current preamp and connected up using an optical cable. It appeared the problem was solved - but no.

Given that this has happened with two different preamp setups (connected by two different wiring types), I think I can rule out wires and external HW. That leaves a potential HW or SW issue with the Mac, an interface issue (I’m thinking the clock issue fits in here), some sort of incompatible software settings, or a seemingly random intrusion by something like Airport or an electrical surge.

Regarding the potential clock issue, is there any way to confirm this without purchasing a new piece of equipment. Is there any way to force the clocks to go out of sync just so that I can hear the effect? I have (what I thought was) a relatively simple setup - just my computer and a Art Digital MPA connected with an optical cable. Am I understanding that it doesn’t matter how simple it is - connect one piece of outboard hardware and the potential for clock issues exists?

I'm going to try to focus on some of the easier things to test so that I can narrow the list. In the mean time, I'd like to hear your thoughts about my observations above.

Thanks again!

just trying to add more clues here.i listened to it again and it's the exact same sound i heard with the aardvark interfaces. in my case, if you right clicked the aardvark tab in the control panel, you could see the two clocks running side by side.
sometimes one would be running at 44.1003.???? don't remenber the exact numbers.
and the other one would start to go 44.1008. or 9 or more.
when that happened, i would hear that exact sound.
i would reset them and it would stop.
can you change the clock speed in the mac to 48k or something other than 44.1 just to do some tests or is it like an onboard audio card. i don't quite get how your running the art into the computer.is it an audio card you bought or do the macs come with an onboard spdif jack.
if it's an aftermarket card with adat in or spdif, there should be a control panel where you can change clock speed and select master/slave.

Again, unless the OP did not list all of his gear, he doesn't have an interface at all. There is nothing to lock the digital signals together.

that's probably it.
im not a betting man but if i was, i would bet those clocks are drifting.
and when they drift to far.....bwwwwwaaaaapppp.

Y'all are correct, I do not have an audio interface. That said, I'm connecting the Mac to the Digital MPA via an optical cable (the Mac has an optical in). Since the AD conversion is being handled by the DMPA, why do I need an interface?

The crackle appears to be completely random and I've not been able to duplicate it "on demand." And, it doesn't happen every tracking session. I purchased a power conditioner yesterday and installed it. Sure did cut out some hum from my monitors. That was nice! I did some recording last night and didn't get the evil crackle. That said, it's way too early to celebrate. I'm going to lay down a track tonight so I'll see what happens then.

I'm doing my recording at 96 khz and I'm confident the clock speeds are aligned (which apparently is different than the clocks being sync'ed).

In answer to some other questions:
- The crackle occurs with different microphones
- I believe that I have experienced this while recording in Cubase and with Audacity. That would rule out the recording software but not the Mac system software.

My neighbor is not a cell tower (thank goodness) - he's a minister (maybe a second responder!).

Thanks again for your help!!

I'm doing my recording at 96 khz and I'm confident the clock speeds are aligned (which apparently is different than the clocks being sync'ed).

Why are you so sure? Which one is the master and which is the slave? The crystal in the computer clock is different that the crystal in the preamp. Connecting via ADAT does not automatically indicate a lock and so the two clocks drift apart now and again. The noise could be bad power but I don't think so.

bassberry, post: 344681 wrote: Y'all are correct, I do not have an audio interface. That said, I'm connecting the Mac to the Digital MPA via an optical cable (the Mac has an optical in). Since the AD conversion is being handled by the DMPA, why do I need an interface?

The crackle appears to be completely random and I've not been able to duplicate it "on demand." And, it doesn't happen every tracking session. I purchased a power conditioner yesterday and installed it. Sure did cut out some hum from my monitors. That was nice! I did some recording last night and didn't get the evil crackle. That said, it's way too early to celebrate. I'm going to lay down a track tonight so I'll see what happens then.

I'm doing my recording at 96 khz and I'm confident the clock speeds are aligned (which apparently is different than the clocks being sync'ed).

In answer to some other questions:
- The crackle occurs with different microphones
- I believe that I have experienced this while recording in Cubase and with Audacity. That would rule out the recording software but not the Mac system software.

My neighbor is not a cell tower (thank goodness) - he's a minister (maybe a second responder!).

Thanks again for your help!!

im gonna have to stick to my conclusion.

-the crackling would be random if the clocks are drifting,they always drift but only drift far enough to produce the crackling ocasionally.they drift in and out.

-when it happens, it would happen with different mics or keyboards or whatever.
the analog source wouldn't matter.

-clock speeds can be linked and still not be in close enough sync.

- the fact that it happened with different hardware proves the issue is with the computer.

-that is a very distinct sound ,i have only heard it in relation to out of sync clocks.

try recording at 44.1 and see if it goes away.the mac card clock might keep up better at 44.1
that would tell you something if it does.

you can never be 100% sure about troubleshooting till you get to the bottom of it but running a pre amp like that into an onboard audio card(that really isn't meant for that application) is likely to be trouble one way or another down the road. imo

either way, if you bought an inexpensive firewire or usb interface with line ins, a couple pre's and dig.in, your problem would likely be solved and you'd have more options.i think you'd get better sound too.poor clocking affects what you hear.

Okay, I'm convinced I need to seriously investigate the audio interface. After browsing the web it appears that those puppies aren't cheap! I'm hoping you can point me to one or more options that are reasonably priced, consistent in quality with my other components, and will get the job done without a lot of bells and whistles (i.e., limited features, but the features it has are good quality). Any recommendations?

Thanks!

bassberry, post: 344685 wrote: snip ..... I'm hoping you can point me to one or more options that are reasonably priced, consistent in quality with my other components, and will get the job done without a lot of bells and whistles (i.e., limited features, but the features it has are good quality). Any recommendations?

TC Electronic Impact Twin is what I recommend. The Lexicon Omega (48k max) has a digital s/pdif and optical port but is not of the quality of the Adam monitors or ART high resolution digital converters (up to 192k). There are some other USB things cheaper but I don't like any of them that I saw.

bassberry, post: 344362 wrote: An electronic “crackle” ruins an otherwise fine track. I’ve spent hours trying to troubleshoot this and, so far, it’s winning. I don’t know what to do as a next step to banish this demon from my system. Any ideas would be appreciated. I’m desperate!

Here's a link to where you can take a listen...

[[url=http://[/URL]="http://buffalo5piec…"]Forum[/]="http://buffalo5piec…"]Forum[/]

I’m not clipping anywhere during recording. I’ve found no pattern to when it shows up. It lasts only long enough to muck up the track and cause me extra work. I record with a 256 Sample Buffer.

I really need some direction about how best to troubleshooting this. Thanks! -steve

bassberry:
maybe try two things:
#1 The ART unit won't work above 50Khz sample rates in ADAT out mode...So I would try setting sample rate at 44.1Khz or 48Khz...the 96Khz is probably whats causing the dropouts and it won't work anyway...doesn't gain you much in terms of sound quality either....It should work best at 48Khz 24bit.
#2 You might want to try SPDIF mode instead which is of course only 2 channels stereo and I don't know if you're Mac has a SPDIF input....

Not to contradict really, but I think the ADAT reverts to Toslink at higher than 48k. Otherwise it wouldn't work at all.

Jack:
This was something I had found at Sound On Sound:
[[url=http://[/URL]="http://www.soundons…"]ART Digital MPA[/]="http://www.soundons…"]ART Digital MPA[/]

"When using the S/PDIF or AES-EBU formats, the sample rate may be selected by means of a rotary switch on the front panel to be 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, or 192kHz. There's also a BNC word-clock input as well as another BNC connector to pass the word clock along to another device. When locking to the ADAT optical input, the sample rate must not exceed 50kHz, which should accommodate the varispeed range of a 48kHz ADAT machine."

So..ya I could be all wet..my thinking was if bassberry were to set his sample rate on the ART to 48khz 24bit it might clear up what sounds to me like a dropout issue losing sync.
I don't know if I fully understand his hookup to the Mac using its optical input as ADAT or how that even works....not sure how ADAT sync would drift....not sure how the Mac does that though or for that matter what bassberry is using for software???
It seems like the SPDIF would be the right way to record into the Mac from this box and not ADAT..
He said he was using 96Khz so that seemed like a plausible correction and worth a try....
How does the Mac translate an optical signal?....what clock?

You're on the right track. So to speak. In fact you'd be right if the OP were actually able to lock the clocks together, but he can't even at 48k because the Macbook built in soundcard doesn't have that option TTBOMK. It might take longer to drift apart at 48k but there are no guarantees. Toslink effectively is optical s/pdif. It isn't as stable as an phono plug s/pdif but I doubt this is a road setup where optical cable integrity is an issue.

Here's the poop on optical.
ADAT format will pass 8 channels of audio at 44.1k or 48k.
ADAT will pass 4 channels of audio at 88.2k or 96k.
ADAT will pass 2 channels of audio at 176.4k or 192k.
Toslink is optical S/Pdif and is only two channels from 192k down.

The reason the DPA II turns to Toslink at higher than 48k is that by design the DPA only reads the first two channels of basic ADAT and passes the remainder unread untouched. At the higher rates it can't pick off the proper channels and so it reverts to Toslink which is always 2 channels regardless of the sample rate.

Of course I may be full of #$%^ too. But this is how I understand the specs of the DPA and the workings of the various optical protocols.

I thought ADAT and/or TosLink/SPDIF generated its own sync clock as part of the data packet protocol and that is what a "receiver" has to sync to....unless you select and use an external word clock or something like the RME FF800 has?
I would think the Mac has a setting in it's sound manager to sync its optical input to either external or internal and then bit rate and sample rate settings...not being a Mac user myself not sure about where that would be but there should be a utility there...
If it does I would think you need to set the Mac to sync "external" meaning it will sync to the incoming ADAT/Toslink signal clock and then make sure the sample rate and bit depth are the same as the ART...
Maybe try that?

ADAT includes this sync info but many prosumer devices will only act as a vague master and no way to alter. Sometimes it isn't determinable whether it will act even as master. The ART DPA can be set to accept basic ADAT timing but would need a word clock BNC connection to sync the higher resolutions. This is again related to the DPA picking off only two channels. There is a button to change the ADAT to S/Pdif and the OP might try this instead. There should be a lock light on the DPA somewhere according to the manual.

I would be interested to know what setting controls the Macbook has. I haven't had a Mac in years. At any rate, the real solution is likely an interface rather than a consumer sound card.

It is interesting were discussing how one should attempt to interface digital optical audio into a computer sound card.....once again! LOL :confused:
The digital facets of the ART being used as an interface via ADAT/SPDIF really should be connected to a proper computer interface bus specifically designed for this kind of thing like USB or FW. But then again bassberry does have sound getting through his Mac and into Cubase and the noise is random...it works! :smile:
So as far as this data sync thing goes....when you convert, generate, transmit data packets that include timing bits...it's up to the receiver to grab those bits as they arrive and latch the remaining data byte into a buffer/register.....which is why it would make sense to set the Mac to external sync rather than internal....the transmitter (ART) is sending data at a specified rate with an embedded clock pulse....the receiver can't change that it can only keep up with it....so if anything is going to lose track of the timing or drift it would seem to me it will be the Mac end...now it may be able to keep up to a point with latching data into the buffers but eventually it will lose track and glitch...but then it must be resetting and keeps going....I don't know if that explains the random or not...but that's what's recorded.....just my thoughts....I'm pretty curious to find out what this noise is....at one point it didn't sound like a dropout....sounded more like clipping....but I don't know anymore...Hehe

I experience a similar situation from time to time. Thankfully it is rare.
It is a clock issue.
I own all Presonus gear (Firestudio, DigiMax LT x2), and can rarely get all three units to work together.
When I'm running two (FS + DM), @ 44.1, the "clicks" still can happen.
Zoom in on your DAW where the sound occurs - REALLY CLOSE - if you see the waveform inexplicably zero for a moment, that's a dropout, and a clock issue.

Sometimes I wonder of the DMs are the issue in my case, but I'm looking at the RME FF800 myself as a solution to this, and other issues...

soapfloats:
Thats whats weird about the sound of bassberry's track though...to me it didn't sound like that abnormal clicking dropout sound. It was definitely a "crackling sound" very light in level and the audio was still there (if you know what I mean).
If bassberry comes back for a report it would be interesting to see if he can zoom in on that segment where the crackling is and see if it zeros out or not. The only time I ever got a "dropout" from my FF800 was when I had the buffers set too low and the FW and my computer couldn't keep up properly...but that wasn't a clock issue...256 buffers works best and that's what I've read is that there is a sweet spot for buffers where the system will remain stable
Do you use a separate word clock for everything or are you using it all ADAT?

Here are some more factoids...
- I use Cubase Studio 5 for recording and mixing.
- The Mac recognizes the input as “Digital In.”
- In the device setup dialog in Cubase, there is a input area that enables the use to choose the clock source. However, for this input device that input area is disabled and “grayed out.”

Soapfloats, you suggest I “Zoom in on your DAW where the sound occurs - REALLY CLOSE - if you see the waveform inexplicably zero for a moment, that's a dropout, and a clock issue.” I did this and it looks like a dropoff to me. I’ve posted a pic of this at [[url=http://[/URL]="http://buffalo5piec…"]Forum[/]="http://buffalo5piec…"]Forum[/]. If I’m reading this right, this is solid evidence of clocking being the issue.

My thought is to purchase an ART SyncGen. It seems like it’s the right tool for the job (since I don’t need more preamps, DA converters, etc. and I want to keep the solution cost as low as possible.

The SyncGen won't work either because it won't sync the computer which is the whole problem. Your built in soundcard does not have options for command and control of the clock which is WHY it's greyed ou in Cubase. Get an interface and be done with it. Problem solved. Well that problem anyway. This cat is skinned.

Just to clear up one or two points:

"Toslink" is a Toshiba proprietary name for a type of optical connector and cable. It does not describe what information can be carried, so you can send ADAT or S/PDIF protocols through Toslink cables and connectors.

Both ADAT and S/PDIF formats are self-clocking. A receiver can always recover a clock from the data stream for the purpose of synchronizing the decoding of the data. Whether this clock is stable enough to be used for other purposes such as clocking local ADCs and DACs is a different matter, and this is a case where a common external wordclock driving both the source and destination of a optical link can make a difference.

AES/EBU data transmission (which is nominally the same protocol as S/PDIF) is by convention carried by differential copper cables and used with external wordclocks, even though the AES/EBU data stream contains all the information needed for clock recovery.

At 48KHz word rates, the bit rate in S/PDIF is around 3Mb/s, and for ADAT is over 4 times higher at around 13Mb/s. The result of this is that optical transmission of ADAT is more sensitive to cable quality and length and also to connector integrity than S/PDIF.

The native optical inputs on Mac computers are always S/PDIF, and will not recognise ADAT protocols. A valid S/PDIF signal present at an optical input will result in that source being selected and that clock being used for audio I/O up to 96KHz/24bit.

Thanks to Boswell for clearing up my muddy explanation and explaining what's happening on the Mac end of things.