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D-75 / Sep 2004
IMPORTANT!
D-75 AD-75 A
D-75 AD-75 A
D-75 A
udio Levelsudio Levels
udio Levelsudio Levels
udio Levels
GeneralGeneral
GeneralGeneral
General
All professional digital audio broadcast consoles manufactured by Wheatstone
are hybrid in nature. That is, they allow the user to connect both analog and
digital domain sources and provide both analog and digital outputs. While this
approach allows for greater flexibility when interconnecting source and
destination equipment, the user must be aware of what levels to expect when
applying, say, a digital input and measuring at an analog output.
Gain StructurGain Structur
Gain StructurGain Structur
Gain Structur
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Broadcast consoles by design have various electronic stages at which the
signal level may be amplified or attenuated. The primary stages are the A-D
converter input, channel fader, DSP mixing and the bus output D-A converters.
The sum of these gain stages is commonly referred to as the console’s “gain
structure”. Wheatstone consoles are factory calibrated for 0dB or “unity gain”
when the input channel fader is set to nominal (-12dB).
The following is a stage by stage breakdown of a typical console’s gain stages:
Analog Input (A-D Converter)Analog Input (A-D Converter)
Analog Input (A-D Converter)Analog Input (A-D Converter)
Analog Input (A-D Converter)
•␣ trim pots located on the ADC input circuit cards are trimmed so that a
+4dBU input signal will yield a -20dBFS digital output with the channel fader
at nominal. Trim pot gain range at this stage allows for interfacing unbalanced
equipment. Mic level ADC circuit cards have trim pots for matching various
microphone source levels to the console’s operating level.
DSP GainDSP Gain
DSP GainDSP Gain
DSP Gain
• set in firmware for unity gain, digital attenuation may be applied on a channel
by channel basis via a dipswitch setting.
Analog Bus Output Gain (D-A Converter)Analog Bus Output Gain (D-A Converter)
Analog Bus Output Gain (D-A Converter)Analog Bus Output Gain (D-A Converter)
Analog Bus Output Gain (D-A Converter)
• trim pots located on the corresponding analog output DAC circuit card are
factory trimmed so that a -20dBFS digital input signal will yield a +4dBu
analog output with the channel fader at nominal. These may be adjusted over
a range of -26 to -10dBFS = +4dBu.
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