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HF Hissing in Recordings

Discussion in 'Vocals' started by asknone9, May 18, 2009.

  1. asknone9

    asknone9 Guest

    So, I'm relatively new at this but I'm learning fast and have read literally days upon days of information on the recording process in the past few months. I'm having an issue with high-frequency hissing on vocal tracks when I'm compressing them. I have a Native Instruments Audio Kontrol 1 and an AT2035 (Previously the 3035). I've tried comparing the amount of hiss I can hear with the gain turned significantly up on the Audio Kontrol, without a (software) compressor. It has no hiss at all even with the knob all the way up. Of course, I couldn't even record most whispers that way without clipping, but it still arouses the question of why I'm hearing hiss when I bring the levels up through compression. In a normal situation I cannot get the gain knob past 10 o'clock without clipping on the loudest vocals, so compression is usually necessary, or at least to my extent of knowledge it is. Is there something I'm missing? Is there a way to get more of the signal from the mic without inviting hiss and without engaging some kind of high cut filter? Also, could 24-bit recording be an advantage to me as a result of a lower noise floor? Thanks for the help!
     
  2. TheJackAttack

    TheJackAttack Distinguished Member

    Compression is a tool best to use with caution.

    Click on this link and read the fourth post down by Shotgun.

    {old-link-removed}
     
  3. soapfloats

    soapfloats Well-Known Member

    That thread's a great one, Jack. I found it while trying to understand compression better awhile back, and had forgotten it. Nice!

    To the OP: That "hiss" usually reveals itself in the "make-up gain" stage. When you compress a signal and use make-up gain, you're boosting EVERYTHING, including all the air/room noise/hiss. If your signal-to-noise ratio isn't too great, this is often the result (being a relative beginner, I've had this issue many times myself).

    Solutions? Less make-up gain, or better yet - less "noise" in the original signal.
    Think about gain structure and signal path. If the noise is at the beginning of that chain, chances are you're only going to accentuate it as you go along.
     
  4. asknone9

    asknone9 Guest

    Wow thanks for the abundance of info! It is much appreciated, and I definitely know a load more about compression. What has me confused however is how I can turn the gain on the preamp all the way up and not have any audible hissing, but make-up gain on a compressor brings that hissing up. Am I correct in assuming that my equipment is quiet enough and the hissing must not be hardware related, in making these observations? Is there a difference in what is happening to the signal when I bring the signal up using a compressor vs. when I am bringing the signal up via the gain knob on the preamp, from a pure volume perspective?
     
  5. NCdan

    NCdan Guest

    A preamp boosts ALL the sound, so yes, the hissing will be louder, but everything else will be EQUALLY louder, which means that the hissing isn't any louder in proportion to everything else than it was before you put the signal through the preamp. Does this make sense so far?

    Compression/limiting puts a ceiling on the "volume level," meaning, the signal is only going to get ___ loud (depending on how you set the compressor). The sound that is at a higher level than the ceiling slams into the ceiling, which means that you won't get those peaks. What is nasty about compression/limiting, though, are the softer sounds, like HISSING, become louder. But the hissing and other undesirable noises are not becoming louder in proportion with everything else, because the loud sounds (aka the sounds you want to hear) are being partially cut off by that compressor ceiling. Does that make sense? So, when you compress and boost, one of the things you are doing is adding more hiss to your mix. I make a point of never boosting a compressor signal unless it's something like a bass that's gonna get low passed anyway. Then again, I only compress the bass because I suck at bass, but that's another topic. :lol:
     
  6. asknone9

    asknone9 Guest

    Alright that makes sense. I've known that compression should be used as sparingly as possible unless used for artistic purposes, but I got to thinking about what happens when a song is limited to bring it up to commercial volume. Then again there's the extra expensive gear to be accounted for and all that. So, I assume you would agree that it would be advantageous in the noise realm to record softer vocals hotter at the preamp level, and only use compressors for peak control rather than bringing up softer parts. I imagine too that in order to record something really dynamic, a hardware compressor would more of use to me since it modifies the signal before reaching the DAW unlike software. Also, how do you feel about 24-bit as it applies to noise?
     
  7. NCdan

    NCdan Guest

    Yes.

    What? How about not using compression for something more dynamic?

    Look, just limit to where you won't be getting any peaks. If the person who played the instrument or did vocals really sucks then you'll have to run gentle compression plugins until any distortion goes away. If you ask me, compression should only be used to smooth out limiting, or if someone is going for a certain sound (intentional pumping, or something like that). I'm sure someone will disagree with me here, but compression is too soft for my tastes by itself. I would rather do a light limit than moderate compression. But hey, that's just my two cents; I'm sure other people here love compression and hate limiting.
     
  8. asknone9

    asknone9 Guest

    By dynamic, I meant something that has a soft parts that become inaudible and/or peaks that near distortion. But everything is making more sense now. One more thing though:

    Are you saying here that something that clips/distorts at the hardware level can be fixed with a plugin compressor after it's been recorded? Thanks again!
     
  9. NCdan

    NCdan Guest

    No. What I'm saying is that limiting, especially digital limiting, can cause distortion on loud parts if more than a small amount is used. The audio is just hitting the wall with limiting. Compression lets more of the signal through the wall. So, limiting sets your hard ceiling and then adding compression after will lessen the peaks hitting that ceiling, which will reduce any distortion caused by limiting.

    Dynamic means playing consistently with different sound levels (emphasis on consistently); generally ppp to fff. If the parts are so quiet that you can't hear them or if there are obnoxious peaks, then it's time to retrack and get it right.
     
  10. asknone9

    asknone9 Guest

    Alright. Many thanks!
     

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