Specifications

2.14
Applications Manual
© 2003-2005 Prism Media Products Ltd
Revision 1.11Prism Sound dScope Series III
3.2.3.8.1 Analogue-to-digital jitter susceptibility
Applies to:
EUTs with analogue inputs and digital audio outputs.
Aim:
To measure the
jitter susceptibility
of the
EUT
when presented with jitter of varying frequency at
its Reference Sync input.
Method
This test can only be performed if the EUT has an AES11 Reference Sync input.
The analogue input of the EUT is driven with a –3dBFS sinusoidal stimulus at fs/4 (where fs is the
sample rate of the EUT). The Reference Sync input of the EUT is connected to the digital output of
the dScope, which is driven with a carrier signal whose phase is jittered with a sinusoidal jitter signal.
The frequency of the jitter signal is varied from 80 Hz to 20kHz in octave steps. The jitter amplitude is
set at the high frequency jitter tolerance limit of the interface, which is nominally set at 1/(512 x frame
rate). The THD+N of the EUT output is measured at each step and then the results are graphed for
both channels.
The measurement may be repeated for other input signal frequencies. Two useful frequencies might
be fs/192 and 997Hz. The operator is asked whether or not to repeat the test for these frequencies.
3.2.3.8.2 Digital-to-analogue jitter susceptibility
Applies to:
EUTs with digital audio inputs and analogue outputs.
Aim:
To measure the
jitter susceptibility
of the
EUT
when presented with jitter of varying frequency at
its digital or reference input.
Method
The digital input of the EUT is driven with a –3dBFS sinusoidal stimulus at fs/4 (where fs is the sample
rate of the EUT). The digital input carrier is phase-modulated with a sinusoidal jitter signal.
The frequency of the jitter signal is varied from 80 Hz to 20kHz in octave steps. The jitter amplitude is
set at the high frequency jitter tolerance limit of the interface. which is nominally set at 1/(512 x frame
rate). The THD+N of the EUT output is measured at each step and then the results are graphed for
both channels.
The measurement may be repeated for other input signal frequencies. Two useful frequencies might
be fs/192 and 997Hz. The operator is asked whether or not to repeat the test for these frequencies.
If the equipment under test has a Reference Sync input other than the digital audio input, then the test
should be repeated with this input driven from the dScope's digital output as well.