possible to make the target levels appear on the printout by programming them into a
tolerance definition, and this is explained in section 5.5. Typical results for the above
example might look like this:
USER LEVELS (+10dB)
1. +9.3 +9.5
2. -0.2 0.0
3. -30.1 -30.3
4. -36.8 -37.7
5. -47.6 -47.8
6. -53.6 -54.1
Because of memory constraints within the LA102 this segment shares results space with
the crosstalk segments. This means that LA102 configuration C must be set to at least 2
if segment K is being used in the same sequence as segments A, B, C or J, otherwise a
Sequence Error 12 will occur and only one of the segments will be stored (see section
4.18 for a more detailed explanation).
The frequency defaults to 1kHz, but any 6 frequencies can be specified by using the ! tone
segment (see section 4.16). This can be useful for accurately testing filters by using an
inverse weighting curve. For example, a CCITT O.41 weighting filter could be tested by
using six tones, corresponding to the filter’s inverse: 200Hz at +21dB, 500Hz at +3.6dB,
1kHz at -1dB, 2kHz at +3dB, 3kHz at +5.6dB and 4kHz at +15dB. The result will show
the deviation from the expected filter response and should be six levels all around 0dB. A
suitable segment would be:
!K 200,1000,+21, 500,,+3.6, 1000,,-1, 2000,,+3, 3000,,+5.6, 4000,,+15
When using the ! tone segment in this way there must be six tones and each tone must last
1s (hence the 1000ms duration in the above example). If only three tones are required
then dummy tones should be used to make the duration up to 6 seconds (otherwise the
LA101 will start the next segment before the LA102 expects it, and a
Sequence Error 8
will probably occur).
Like any other segment a tolerance can be specified for segment K and this can greatly
simplify filter and equaliser testing. This is also useful because it allows target levels to
be included on the printout.
Filter testing
4.14 Maximum Output Level (MOL) Segments (H, h)
A tape’s maximum output level (ie the level at which 3% total harmonic distortion
occurs) can be measured at 1kHz using segment H or 315Hz using segment h. These
segments sweep the level in small steps over an 8dB range and record the level at which
3% THD occurred. Note that the MOL result is the absolute level out of the system and
not the level into the system. For example if a tape machine has an overall gain of 4dB
and the measured MOL is +7dBu then the input level which gives 3% distortion is
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4. User Defined Sequences
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