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Source of unknown crackling

Discussion in 'Recording' started by bassberry, Mar 21, 2010.

  1. bassberry

    bassberry Guest

    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...


    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
  2. TheJackAttack

    TheJackAttack Distinguished Member

    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.
  3. boxcar

    boxcar Active Member

    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.
  4. Shadow_7

    Shadow_7 Active Member

    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.
  5. bassberry

    bassberry Guest

    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!
  6. Shadow_7

    Shadow_7 Active Member

    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.
  7. bassberry

    bassberry Guest

    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
  8. Shadow_7

    Shadow_7 Active Member

    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.
  9. TheJackAttack

    TheJackAttack Distinguished Member

    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.
  10. boxcar

    boxcar Active Member

    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.
  11. TheJackAttack

    TheJackAttack Distinguished Member

    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.
  12. boxcar

    boxcar Active Member

    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.
  13. bassberry

    bassberry Guest

    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!!
  14. TheJackAttack

    TheJackAttack Distinguished Member

    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.
  15. boxcar

    boxcar Active Member

    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.
  16. bassberry

    bassberry Guest

    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?

  17. TheJackAttack

    TheJackAttack Distinguished Member

    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.
  18. djmukilteo

    djmukilteo Well-Known Member

    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....
  19. TheJackAttack

    TheJackAttack Distinguished Member

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

    djmukilteo Well-Known Member

    This was something I had found at Sound On Sound:
    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?

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