In article writes:

I'm curious, in the context of feeding a soundcard's input -- how common
is the problem of a preamp/device (especially a +4dBu one) lacking
'headroom', and for -which- sound cards? Or did the author mean 'plenty
of gain for accommodating low level sources'?

No, he meant plenty of output capablity (lots of volts) which some
digital equipment takes in order to reach full scale level. It doesn't
matter how much gain you have. If it takes 5 volts in order to reach
full scale digital level and the preamp clips at 4 volts output, it has
insufficient headroom for the application. If it took only 2 volts to
reach full scale, then it would be adequate.

A related question, on digital devices with analog inputs (-10dBv or +4
dBu) -- Is there a standard (or common practice) for the specification
of what input level converts to 0 dBFS (not clipped)?

No. This is why there are so many questions about it. They seem to
range from -20 dBFS to -12 dBFS for whatever the nominal (+4 or -10)
input level is. If +4 dBu gives a level of -20 dBFS, you'd need a
preamp that could put out at least +24 dBu in order for the recording
to reach full scale. Of course you need as much gain as is necessary
to get the input up to +24 dBu, but that's a different issue than
headroom.

If these things had input level controls like any civilized tape
recorder, you could set it up to whatever worked for you, but since
they don't, you have to make whatever you have work.


--
I'm really Mike Rivers - )

Mike Rivers ) wrote:
If these things had input level controls like any civilized tape
recorder, you could set it up to whatever worked for you, but since
they don't, you have to make whatever you have work.

I assume you're suggesting the ability to calibrate the 0 dBFS setting
of the ADC (as opposed to an adjustable pad and/or bump box on the
inputs). I don't have knowledge of ADC design to guess what it would
cost to add the functionality of fine calibration of 0 dBFS, though I
know some interfaces can be toggled to generally accomodate -10 or +4
gear. Speaking of which, I just remembered (doh) that the RME Multiface
allows one to make similar changes via internal jumpers. looking it
up Each analog input and output can individually be configured to one
of three settings of 0 dBFS:

19 dBu
13 dBu [default]
2 dBV (4.2 dBu)

I don't have equipment to verify this.

- Brian