4.9 Crosstalk Segments (A,B,C,J,c)
Crosstalk segments A, C and J measure crosstalk at six frequencies (40, 100, 315, 1kHz,
6.3kHz and 10kHz) taking 1s per frequency. The result is always calculated relative to
the ‘TL OUT’ level as for noise measurements. Segment C operates at 0dB, while
segment J operates at -10dB (as specified by the IBA for tape testing). Segment A is
similar to segment C but has 50µs de-emphasis applied to avoid overload when testing
FM transmitter systems.
Segment B is a fast crosstalk segment which takes 2s and produces crosstalk figures for
100Hz, 1kHz, 6.3kHz and 10kHz (½s each tone, default level is 0dB), but for very
accurate low level crosstalk measurement it is best to use segment C or J. Segment c
measures crosstalk at 15kHz and 0dB.
Since crosstalk is a relative measurement it is important that the crosstalk segment is
always preceded by a test level segment (T or V) otherwise a
SEQ ERROR 13 will be
generated.
Note for experienced users: The crosstalk result is the level of crosstalk relative to the
measured level of the interfering tone. Since the interfering tone may not be connected to
the other input channel the LA102 does not attempt to measure it. This means that
meaningful crosstalk measurements can still be made when only a single channel is
connected to the LA102 L input providing both output channels from the LA101 are
connected to the device under test.
The LA102 must therefore calculate the level which the interfering tone on another
channel would be measured at were it present. It assumes that this is equal to the
crosstalk measurement level plus the gain of the system and it calculates the latter from
the measured TL OUT result less the Test Level measurement level. For example, the
sequence T0C6 is run and the TL OUT is +10dB. The absolute crosstalk level is -40dBu,
so the relative crosstalk is -40 - (+6+10-0) = -56 since the LA102 assumes that the
interfering tone would have been measured at +16dB.
The test level and crosstalk segments can therefore be run with any measurement level,
although it is good practice to keep the test level segment at the test level.
4.10 Distortion Segments (D,E,F,G,I) Distortion segments
Segment D measures distortion at three frequencies (100Hz, 1kHz and 6.3kHz) in 6s at
+8dB (by default), and is generally used for quick distortion measurement. Similarly
segment E measures distortion at 100Hz +9dB, 1kHz +9dB and 1kHz -10dB in 6s.
Segment I measures 100Hz and 1kHz distortion at +8dB and -10dB.
Where more frequencies are required, segment F can be used as it measures distortion at
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4. User Defined Sequences
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