Sonnox Oxford Limiter - Manual (Page 14)

8 RECONSTRUCTION METERING SECTION
8 Reconstruction
Metering
Section
An important fact, which is often overlooked, is that in any discrete time sampling system,
it is possible to create sample values that may not be decoded and reconstructed
correctly. Whilst it is true that,
if
left
unchanged, a signal properly converted into the
digital domain by a perfect ADC will always produce sample values that can be legally
decoded in a perfect DAC, further processing of those samples can result in a decoded
signal that is illegally high, and therefore may not be faithfully reproduced, even if no
sample value limiting occurs.
The following is an illustration of one example of this situation.
With a signal frequency that is exactly 1
4 of the sample rate, and in phase (ie. 12KHz at
48K or 11.25KHz at 44.1K) it is possible to generate full level output from a DAC from
samples that barely reach 70% of full value within the digital domain.
If the level of this signal were increased towards maximum allowable sample value (close
to
± − 1) the area representing the DAC reconstruction filter would produce signals that
are considerably in excess of maximum modulation.
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