Mike Rivers (that's me!) wrote:

The Mackie recorder with analog I/O clips at +24 dBu. I was under the
impression that most sound "professional" sound cards ran somewhere in
the ballpark of +16 to +16 dBu for 0 dBFS.

I would expect "consumer"
and "-10" cards to reach full scale in the +10 to +12 dBV range.


I must not have been fully awake when I wrote that. How about in the
ballpark of +16 to +24 dBu for 0 dBFS for a "pro" level card and in
the ballpark of +2 to +8 dBV for a "consumer card."

Which is in the ballpark of Kurt's RME card.

Of course, you understand the concept of properly setting system levels to
maximize overall headroom. I fear that in these digital days, that is no
longer being drilled into the heads of newbie engineers the way it was for
many of us.

People talk about headroom in a digital system, but there really is
none - It's only what you make. And more often than not, you don't
have all the knobs you need in order to get the headroom you want to
have. Ideally you should use all the gain you can get at the mic
preamp without clipping, so the input gain control on the mixer or
preamp not only sets the minimum noise floor, but also sets the
headroom at the front end. So you set the gain so that when the singer
is bellowing as loud as he can, you're running at what you think is a
safe margin below clipping of the preamp, say 6 dB.

Now, if the preamp is putting out +18 dBu with that bellowing singer,
it can put out +24 dBu before it clips. But if your sound card has no
input adjustment but a +4/-10 switch, and IT reaches full scale at
+19 dBu like your RME card does, you have only 1 dB of headroom.
Ideally, you'd want to attenuate the input to the sound card a bit so
the preamp can go its full range without the recorder clipping, but
there's no knob for that. (remember when recorders used to have knobs
or trimpots for record level?) So you do the next best thing and back
off on the preamp gain to leave yourself some headroom on the digital
side, but that possibly compromises the S/N ratio.

In real life, you don't ponder these things, you do what works.


--
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