Sample Rate
On the
Sample Rate
button you can select the sample-rate of the A/D converter between 32
kHz, 44.1 kHz, 46 kHz, 64 kHz, 88.2 kHz and 96 kHz. When a sample-rate has been selected,
the A/D converter will take about 3 seconds to calibrate before it is ready for operation. The
sample-rate LEDs will always show the selected sample-rate. When an external
synchronisation is selected via the
Ext. sync
button, the sample-rate LEDs indicate the
sample-rate of the received external synchronisation signal.
Dither
On the
Dither
button you can select the amount of dither added to the audio signal when
sampled by the A/D or the D/D converter. The dither setting has to correspond to the bit
resolution of the digital system to which the digital output of the converter is connected. If the
audio signal is sampled in 24 bit resolution and connected to a 16 bit hard disk recording
system, the noise behaviour of the recorded signal will not be optimal, and a clicking in the
sound can occur. Therefore it is important to set a correct bit resolution.
Sync.
On the
Sync.
button you can select the synchronisation source for the A/D converter sample-
rate. The source can be Int. Sync which is the in/-5ppm precision oscillator. External
synchronisation, which is the AES11 reference, signal connected to the Ext. Sync. input
connector on the rear panel. Finally, the synchronisation source can be the digital input
selected via the digital input
button. If no Ext. Sync or digital input source is connected to the
ADDA 2402 the source can not be selected via the Sync. button. If a selected external
synchronisation source fails, the ADDA 2402 will automatically default to Int.Sync.. If the
signal is re-established the ADDA 2402 will automatically switch to the selected source
unless the synchronisation mode has been changed.
It is possible to detect the sample-rate of an incoming digital signal. Set the digital
Sync
selector in digital input mode and use the
Digital Input
selector to select the digital input
source you want to detect. The sample-rate LEDs will now indicate the incoming sample rate.
Please note that an incoming signal with a sample-rate of 64 kHz will be indicated as a 48
kHz signal, because 64 kHz is not defined in AES3 as a valid sample-rate (however the
converter will D-to-A convert an incoming 64 kHz digital signal correctly).
Power
On the
Power
button on the right side of the front panel the converter can be set to a stand-by
mode, where the power to the electronic circuits are disabled. By pressing the Power Button in
stand-by mode, the converter re-enters the operation mode, with all power restored. If the
main switch on the rear panel is switched off there will be no power on the ADDA 2402.
The Peak Meter
The ADDA 2402 is equipped with a very precise Fast Peak Programme Meter (PPM) for
monitoring the level of the analog input signal. The PPM indicates the fast peak value of the
signal with an integration time of 10ms for full scale reading according to IEC 268-10. The
meter has a hold time of 1 second for levels from –12 dBFS to 0 dBFS. Levels below -12 dBFs
has no hold function.
The peak meter reads out the fast peak value of the input signal in dB full-scale (dBFS), where
reading is relative to the full-scale value of the digital signal. This means that for the XLR
input an analog level of +18 dBu, which is 6.16Volt RMS, will give a 0dBFS reading. A red
LED indicates 0dBFS. For –20 dBFS to 0dBFS the readout resolution is 2dB. From –12 dBFS
to –2dBFS the readout is indicated by green LEDs.
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