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Laptop Monitoring Levels

Discussion in 'Sound, Music, and Intercom' started by DCATTechie, Dec 4, 2008.

  1. DCATTechie

    DCATTechie Active Member

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    I'm a lighting guy so please excuse my limited knowledge and vocabulary. The LED's that show the audio level on my highschool's sound board are completely dead. Therefore, I don't know if the signal is peaking(unless i hear it which is rare) or the signal is about to peak and I need to adjust levels. My question is, is there a way to run the signal through an external sound card attached to my laptop running a program to monitor the signal levels? My card is an M-Audio Fast Track Pro.
     
  2. anonymous381

    anonymous381 Member

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    I'm gonna say there IS something but where and what that something is I don't know I know there are mini-mixers with LED's on them for ~$100 but of couse that would be the long way around an easy fix.

    Samson Audio - MDR6

    thats the minimixer I just bought and it works and sounds great. you can find it for about $100 if you look around
     
  3. lieperjp

    lieperjp Well-Known Member

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    Ah, I'm trying to think of this cool thing we had at my high school - it looked like an equalizer but it was just columns of LEDs that lit up for each frequency... Now I can't think of what it was called. It also doubled as a white noise generator, not that we ever used it... :(

    Doing a bit of google searching, you might be looking for some type of spectrum analyzer - but those look pretty pricey - and I'm not sure if that's too detailed.

    Also, you could look into getting it fixed, we just had the one on our Mackie board fixed, it cost us around $30, but I think we get a special deal :grin:
     
  4. FMEng

    FMEng Well-Known Member Fight Leukemia

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  5. anonymous381

    anonymous381 Member

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    looks like you would have fun whacking wires with the RU-SM16!!!! the Phase 3 looks a little nicer to work with
     
  6. TimmyP1955

    TimmyP1955 Active Member

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    It would be simpler, and likely more cost effective, to just get the mixer repaired.
     
  7. Chris15

    Chris15 CBMod CB Mods Premium Member

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    Many a mixer will meter a source that is being PFL monitored. If you add an external VU meter, sure you can see what's happening on the main outs but you lose the ability to meter an individual channel which would likely allow you to track down a clipping source...
     
  8. Footer

    Footer Senior Team Senior Team Premium Member

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    Its called a real time analyzer, or RTA. Its used to "ring out" a system.

    They do make external meter bridges, but they are not cheap. I want to say there was a large thread about this a year back or so. From what I recall, they are more expensive then they are worth. I would look at how much it would run you to get your board fixed.
     
  9. mixmaster

    mixmaster Active Member

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    Fix the mixer. I looked into this a couple years back and it was cheaper to send it in for repair than buy the parts to build the external meter bridge. RDL has a couple meter modules but they list for a couple hundred a piece last I checked.
     
  10. museav

    museav CBMod CB Mods Departed Member

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    You would also have to calibrate the external meter. This gets into the whole "what does 0 on the meter represent" issue which varies from console to console, on some consoles it could mean you have no headroom and are clipping, on others it could be the direct dBu level while on others it could be the level re: +4dBu or some other reference value. Then there are the meter ballistics, is it more a loudness or VU meter that better tracks the perceived level but smooths out peaks or more a PPM meter that better shows peaks but not averages.

    When you start using a software program you are then likely monitoring digital signal levels after the analog input of the interface and the A/D conversion rather than the actual analog level out of the console. Even the clip indicator on the front panel of the interface might not be much help as it is indicating when the interface input clips and not that the console output clipped or not.

    So another vote for just getting the console fixed, it could be something very simple.
     
  11. Chris15

    Chris15 CBMod CB Mods Premium Member

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    Do we have a regional difference? It would be called a spectrum analyser down here because it's showing you the audio spectrum... I should hope it were real time... Those relics were built in today's digital age of memory...

    Re meter calibration, if it is in real dBu, what should we be mixing to peak at, 0 or -10? Talk to our broadcast brothers and they'll tell you -10...
     
  12. lieperjp

    lieperjp Well-Known Member

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    I've heard of it as a Spectrum Analyzer as well... That's the name I couldn't think of.
     
  13. museav

    museav CBMod CB Mods Departed Member

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    Both get used but I think Real Time Analyzer is more common for audio spectrum specific devices as Spectrum Analyzer is often used to reference an RF spectrum analyzer.

    How about +8dBu? I believe the -10dB reference used in broadcast is dBFS for digital metering, which using their standards equates to a +8dBu analog level. Part the the broadcasters concern is not overmodulating as their output is legally limited and tied to a known input level. Another factor is interoperability, being able to move signals or share media between multiple broadcasters.

    Live sound does not really have these same issues and many devices do not clip until the signal level is +18dBu or greater. Mixers themselves use different ballistics and 0 references for their meters, you cannot at all assume that a console meter it is actually metering peak dBu levels. "dB" is simply a ratio of a level to a reference level and some console meters calibrate 0 on their metering to be +4dBu or what is considered nominal line level while others may even use their maximum output and place 0 at the very top of the scale. Even if two different consoles do use the same 0 reference, that does not mean you necessarily run them the same as one could have a higher maximum output level than the other. And that isn't even getting into whether the meter ballistics are showing more peak or average levels or digital level metering, The important thing is to understand what the metering you have actually represents.

    One common mistake is to look at just the the meters and not factor in the fader. If the meter is post fader, which is typical of almost every output meter, then the actual signal level is a composite of what you see on the meter and the fader level. If the the fader is at -20 then the signal coming into the fader may actually be something like +24dBu and into clipping despite the meter showing 0. While proper console setup should avoid this situation, it is still a good idea to consider what you are metering and how the other control settings affect it.
     

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