Telos Zephyr, User Manual

Page: 45 / 258

Section 3 ZEPHYR AT A
GLANCE
45
found in section 8 (Detailed Menu Reference) and the Appendix.
The limiter engages at 15 dB above the nominal operating value, giving this much
“linear” headroom. There is then another 10- 20 dB headroom provided by the limiting
action.
It is possible to bypass the send limiter. See manual section 11 (Technical Information)
for details on how to do so.
Advantages and reasons for doing so:
•
Dynamic range increases by 7dB, this may be desirable, particularly in non-
broadcast applications.
•
Total harmonic distortion (THD) + noise drops significantly with limiter
bypassed, this may be desirable, particularly in non- broadcast applications.
•
If another limiter will be used. Caution: use of non- linear processing such as
clipping, multiband compression etc. are not recommended before any
perceptual coder
. Contact Telos Systems customer support for a paper delivered
at the AES by Frank Foti on this subject.
Disadvantages and reasons for not disabling the limiter:
•
THD and Dynamic range are quite acceptable with the limiter engaged.
•
Loss of send level control; this control is disabled when the limiter is disabled,
source must be 4 dBu nominal (see appendix for additional information on
levels). External gain stages or pads may be required.
•
Tight control of the level before the Zephyr must be maintained or digital
clipping of the A/D converter could result.
DEEP TECH NOTE!
The limiter activity depends upon the peak-to-average ratio of
the program material and may appear to operate at less than
15 dB above nominal with some audio as input.
Audio input levels above +4 dBu nominal require an external
pad.