Universal Audio UAD Plug-Ins ver.7.5 - Manual (Page 167)

UAD Powered Plug-Ins Manual - 167 - Chapter 14: Fairchild Tube Limiter Collection
Headroom Overview
The Fairchild hardware units can accept an analog signal level of approxi-
mately +27 dBm before undesirable signal clipping occurs. As the signal in-
creases up to this point however, desirable audio-path nonlinearities and
“good” harmonic distortion characteristics occur. This musically pleasing
“warmth” at higher levels is what gives the unit much of its revered sonic char-
acter. Because analog mixing consoles can typically output high signal levels,
audio engineers often take advantage of the ability to “push” the hardware
unit into the colorful arena.
This complete pallet of sonic nuance, including the dynamic input response,
is captured in the Fairchild Tube Limiter Collection models (but not the Fair-
child 670 Legacy). The 660 and 670 plug-ins are calibrated internally so that
when the Headroom control is at its nominal value of 16 dB, 0 dBFS at their
input is equivalent to an input level of approximately +20 dBu on the hard-
ware, where the coloring is more prominent. The result is that a typical signal
within a DAW will drive the UAD Fairchild 660/670 into these “virtual”
higher levels, resulting in fairly high amounts gain reduction.
Headroom Control
The Headroom control (labeled “HR”) is provided to accommo-
date applications where high amounts of gain reduction are not
desired. Headroom simply lowers the internal operating level so
that the plug-in is not “pushed” into gain reduction as much.
Note: There is only one headroom parameter. Although the HR control ap-
pears twice in the Fairchild 670 window, they are permanently linked.
Headroom can be set (in dB) to 4, 8, 12, 16, 20, 24, or 28. The default value
is 16 dB (when the set screw “dot” is in the straight up 12 o’clock position).
Note that Headroom is increased as the dB value decreases.
Tip: Click the “HR” text label to return the control to the default value.
At higher dB values (clockwise rotation), signals will push the plug-in into gain
reduction (and more non-linearity and “good” harmonic distortion color)
more easily. Set the control to a lower value (counter-clockwise rotation) when
less gain reduction and less color is desired.
Note: To avoid the temporary gain increases that can result when adjusting
Headroom, automating this control is not recommended.