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165 Views 3 Replies Latest reply: Dec 2, 2012 8:34 PM by ArneLine6 RSS
emmebbi Just Startin'
emmebbi
11 posts since
Nov 4, 2012
Currently Being Moderated

Dec 2, 2012 3:53 PM

But...where is real 0 db??? too low rec level

I tried to understand why of so low level of recorded files. I did some tests, but I do not find any answer, please help me to understand.

 

First of all I disabled all kind of in/out effects (hp filters, comp, eq, limiter etc etc), so the signal flow directly from input to output....

 

TEST1: I tried to play a REAL 0 dB file directly from the SD card (file taken from a professional audio test cd) but the mixer level meter play it showing absolute maximum vu meter scale at +15db..... why? It is not correct, the file is a REAL 0 dB, the vu meter 'd show 0 dB.

 

TEST2: I tried to play the 0 REAL dB on a cd player. Then I put the analogue consumer CD line output (-10dB) into M20D line 1/2 inputs... using autotrim, gain is set to +5db, so level meter shows 0 dB, but if you try to record, the level remain more than 10 dB under REAL 0 dB..... So I tried to gain manually 10 dB more .... but the recorded level is still very far from REAL 0 dB.... and this is incredible.

 

This is my answer: do the mixer have an automatic gain reduction, to avoid some kind of distortion???? Perhaps this is one of the secret of the mixer good sound? I don't know, but if it's true, we user must know it, and we must know how many dB the mixer work under REAL dB level, because in any kind of situation, LEVEL OF RECORDED FILE IS REALLY TOO MUCH LOW

  • ArneLine6 Line 6 Support
    ArneLine6
    172 posts since
    Mar 14, 2012
    Currently Being Moderated
    Dec 2, 2012 6:04 PM (in response to emmebbi)
    Re: But...where is real 0 db??? too low rec level

    If the "REAL dB" you are referring to means dBFS, digital fullscale, that is at + 15.4dB at the M20d's meter.

     

    If you are referreing to the main mix you have to consider that the main mix is recorded post master fader. If you have a level of, for example, +5dB and the master fader is very low, at -40dB, you have a very low level on the recording.

    The levels on the M20d'd meters refer to analog dBu. If you see 0dB on the main meter this means that the analog signal at the output is at +4dBu, which is the usual nominal level in pro audio.

    dB itself is not an absolute unit for levels. It is a logarithmical scale that needs a reference. The M20d's scale refers to nominal leve 0dB= +4dBu.

    The file you are referring to seems to be at 0dBFS, which is digital fullscale. The maximum before clipping. Athe M20d's scale 0dB on the meter = -15.4 dBFS= +4dBu at the analog output.

    If you would try to record at 0dBFS everything slightly above that would be clipping. With music this would not work. You can, of course, turn up the levels manually to have less headroom and a hotter recording. The mixer does not automatically change mix levels. Most digital live mixers have their "green" range around - 15 to -20 dBFS. As mentioned before, nothing prevents you from just turning it up and the mixer will not automatically change your mix. The mixer does prevent clipping on the inputs when you use trim tracking but this is automatically made up after the pre amp so there is no change in levels. This also only happens if you are really clipping the input.

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