Converters and Low Analog Input Levels?

Robert Katz 1 Comment

I’m wondering why many high end stereo A/D’s have relatively low analog input levels. Most pro consoles and gear are clipping at >24 dBu. However take a look at some sample A/D default input levels referenced to 0 dBFS:

  • Cranesong HEDD +16 dBm (manual doesn’t state if this is max)
  • Mytek AD +19 dBu
  • Apogee Rosetta +20 dBu (can adjust to +24)

Why the “missing” headroom? Is it because full program material generally requires less headroom? This would assume all audio is pop music! What am I missing, something simple I am guessing.

Well, the Cranesong is completely adjustable, I’ve been able to set it to +16 dBu max through at least +24.

We have a Mytek 192 and it’s adjusted to +24 dBu so it must be adjustable though I forget how we did it!

The answer I think is a combination of incomplete documentation and a bit of ignorance or assumptions on the part of the designers. Many of them assume people will be using the converters for mixing with consoles that have VUs and the mixes will have a crest factor of 14 dB or less and that the users will want to “slam” the converter meters. A lot of assumptions, eh? A “perfect” A/D converter in my mind should be able to accept up to (or beyond) +24 dBu = 0 dBFS as a maximum and as a minimum have sufficient gain to accept +10 dBu = 0 dBFS, but I’m willing to accept +15 dBu = 0 dBFS, which should cover a wide range of circumstances.

Comments 1

  1. Dear mister K.,

    Thanks again for sharing your insight.

    2- Non-mastering use might differ, in that clipping 1st gain stage yields more consequences than an A/D unit behaving likewise in the final race ————————————> a goth engineer I know wrote a memoir about clippings in digital/analog realm{s}.

    3-
    Some resistivity factor [like reactance or intrinsic limits in circuits response] must come into play as for setting right values for given applications.
    This could be of the reasons why, for instance, RME set many stock units with max.i.l. @+19 dB,
    which is above your lower & median boundaries.
    _ _

    On faithful behalf of your no-‘stupid loud’-masters following, Lucas
    +33 6 83 02 57 72

Comment on this FAQ

Your email address will not be published.