Safety Recorder Levels

egproductions

egproductions

Veteran
What is the better of two approaches:

1. Set recorder levels to be consistent with mixer levels. When mixer peaks, recorder peaks.

2. Set recorder levels low enough to never peak even if mixer is severely peaking.

The drawback with #2 is that if my mixer levels are in appropriate ranges the recorder levels will be low and will have to be raised in post.

I am using a mix pre-d and going into an h4n or camera as a recorder.
 
The premix should have pretty damn good limiters, so I would set it up so that it limits the bad peaks, and set the recorder so that when the limiter on the mixer kicks in, it's not clipping. That way you should get good levels, and be able to control the loud sounds.

You say safety recorder, is sound being recorded elsewhere?
 
Thank you stiffman, no this is the only recorder, just couldn't think of a better title.

I hear what you are saying but would you go as far as to never let the recorder clip even if it means a somewhat weak signal on the recorder (i.e. -12db)? For instance I currently have it so that when my Mix Pre-D peaks the H4N reaches -12db. If the Mix Pre-D severely peaks the H4N gets right under 0db.
 
Your MixPre has a tone generator that will output a sinewave at 0dBu. Turn on the tone and adjust the recorder input level so the tone reads -18dBFS on the recorder's meter. (This is the EBU standard, a little hotter than the traditional SMPTE alignment level but more in keeping with digital recording practices.) Turn tone off and don't touch the recorder's level controls again; all further level adjustments should be done with the mixer's input pots. While recording adjust the mixer level controls so the mixer's VU meter (solid line of illuminated LED's) hovers around 0 with occasional flickers of the +4 LED. Setting up this way gives you a good overall recording level with sufficient headroom before the recorder approaches clipping. You should not set the levels so high that you're consistently hitting the limiters . Niether the mixer nor the recorder meters should ever "peak" if by that you mean hit full scale; full scale on a digital recording device's meter means you're clipping. The MixPre meter's 0VU level, the top of the orange LEDS, is its nominal operating level. On real speech, when the solid line of LEDs is reaches the 0VU mark the single peak-indicating LED will be about 8dB higher. You're right on the money when the top orange (0) LED is illuminated and the bottom red (+4) LED occasionally flickers. The limiters will kick in if there's a peak where the signal hits +18dBu unless you've lowered the threshold. With the alignment level at -18DBFS, the mixer's limiters kick in just before the recorder peaks, ie, clips.
 
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Keep in mind the nominal line level input on the H4n is -10dB (via the unbalanced 1/4" input), it's input stage subject to clipping peaks if over the +2dBu max (as I recall) The MixPre's output can have peaks up to +22dBu... so using the MixPre's Tape-out would be recommended, or appropriate attenuation in an unbalanced configuration if the using the MixPre's XLR outputs.
* BTW, SD states: "To unbalance, use pin-2 as signal and pin-1 as ground, pin-3 should not be grounded." (contrary to conventional 'balanced to unbalanced wiring')
 
I do basically what Steve recommends. Right about where he tells you to set it is where the limiters will kick on in time to save a clip. I always check that by getting VERY loud at the mic (to make the limiters kick in) and then check that I didn't clip on the recorder.

Once you have done that you can push the levels up a bit if you want because you know you are not going to clip.

Part of the whole -12 thing is related to analog recorders and leaving enough headroom so you didn't clip and getting high enough to get out of the noise.
Digital helps on the low side and the limiters help on the high side. In post I don't have any problem with hot recordings as long as you didn't clip. I would much rather lower your takes than have to boost them.

So this set up not only doesn't "lower your levels" it allows you to raise them a bit safely.

You don't want to clip, and you really don't even want to hit the limiters, but surprises happen.
 
egproductions said:
What is the better of two approaches...
Click to expand...

Neither. I do close to what Steve suggests. I think much confusion comes from the fact that most digital recorders have meters which show you dBfs, while the SD equipment meters show you dBu. Not the same thing.

So what the recorder is telling you is where clipping occurs (at 0 dBfs, so you have to be below that to not clip, which is the advice of peaks around -12 dBfs). The mixer, OTOH, is showing you information related to where mag tape would saturate out. For the mixer, 0 dBu is just the start of the safety zone. People routinely record with levels above that, but how far above that depended on the heads, the tape, and the maintenance. Without tape, this doesn't make much sense, at least to me. But... that's the way SD does it.

Given that, what I do is use the mixer's 1kHz tone to set my recorder to -20 dBfs and then tuck it away (sometimes I gaff tape the controls to make sure they don't move off my calibration) and do everything else at the mixer. I record with my peaks just setting off the red LEDs on the mixer, which IIRC is around +8 or +10 dBu. When I do this, and check the meter on the recorder, sure enough it's showing -12 dBfs. Which is exactly what I want. I leave the limiters set to the factory default (+18 dBu). The mixer itself starts clipping at an indicated +20 dBu, so setting the limiters at +18 dBu effectively prevents clipping at the mixer. And this by default effectively prevents clipping at the recorder.

It's safe, it's clean, and it gives an excellent signal to noise ratio. What more can you want?
 
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