component of motion along the groove equivalent to flutter. This can be measured using
W&F option 8 which selects a flutter measurement with special filtering to read only
flutter components around 300Hz (3.15kHz and 315Hz tones can also be used). The
measurement is normally made using a test disc to DIN45542 and complies with the
current ITC (IBA) requirement (DIN45411).
2.19 Standards CCIR weighting filter
The measuring options meet appropriate world standards: Noise CCIR468-4 weighted
and unweighted (supersedes 468-1, 2 and 3); Rumble IEC98, DIN45539, BS4852 (except
slow response); ‘A’ weighting IEC179; VU response ANSI; PPM response IEC268-10
type 2, BS4297-1968, BBC ED1477 (except scale details); W&F IEC386, DIN45507,
CCIR409-3, BS4847; FIM DIN45411; 2nd order difference frequency distortion IEC268-
3 (note 70Hz used in place of 80Hz). See appendix G for frequency response graphs.
2.20 400Hz High Pass Filter
toggles a 400Hz high pass filter which is useful to ensure that measurements are
not being affected by mains hum. It will operate on level options 1 to 5 and noise options
2 and 3, but not on any other measurement.
HPF is displayed briefly to indicate the
selection, or
CAN'T if the filter cannot be switched in for the measurement (crosstalk for
example).
FLAT is displayed on return to a flat response.
Note for experienced users: The 400Hz high pass filter is actually provided as level
options 11 to 15 and noise options 12 and 13 (see table 2.2) and can also be selected by
pressing
(press to return to options 1 to 5). merely
provides a quick way of toggling between options 1 to 5 and 11 to 15 (see section 2.7).
2.21 Impedance & Impedance Correction (ZC) Impedance correction jack sockets
cycles round impedances on both units. The LA102 provides 10k or 600 inputs
as displayed, at both the front PO jack sockets, and the rear XLR sockets (which are
connected in parallel). The LA101 is more complex, as only the front jack sockets
change impedance (75
or 600 ), the rear XLR sockets are always 10 . The XLR
connectors are therefore optimised for studio equipment testing, in line with the standard
practise of feeding high impedance inputs from a low impedance output, while the jacks
are optimised for 600
line tests.
The letters ‘
ZC’ which appear when 75 or 600 outputs are selected signify ‘Z-
correction’, meaning that the open circuit level has been boosted to give the specified
level into a 600
load. Pressing will toggle between uncorrected and ZC mode as
shown at the top centre of the display (this setting is stored for each impedance even when
the unit is turned off). With the level uncorrected (ie no ZC displayed) the LA101
displays the open circuit output voltage in dB(0.775V), indicated by the symbol dBu. ZC
30
2. Manual Operation
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