Apple Desktop Computer manual Total harmonic distortion

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C H A P T E R 3

Devices and Ports

Total harmonic distortion plus noise (THD+N) as a percentage of full scale for various outputs are shown in Table 3-3.

Table 3-3	Distortion speciﬁcations

		Total harmonic distortion
Connector and level		and noise
Line input		0.03%
Line output		0.03%
Headphone jack, open circuit		0.03%
Headphone jack, 32-ohm headphones,		0.1%
–20 dBFS level
Headphone jack, 32-ohm headphones,		1.0%
–1.5 dBFS level

The signal-to-noise ratios (SNR) for various inputs and outputs are shown in Table 3-4. The values shown are unweighted; values with A weighting would be about 8 dB higher.

Table 3-4	Noise speciﬁcations

Connector and level		Signal-to-noise ratio
Line output		92 dB
Headphone jacks		86 dB
Line input		85 dB
Internal CD		82 dB

38Sound System

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Contents Apple iMac Computer Page Contents Devices and Ports RAM ExpansionSoftware RtasAppendix Abbreviations Index Rtas NV-RAMFigures and Tables Page Contents of This Note About This Developer NoteMac OS PowerPC G3 MicroprocessorSupplemental Reference Documents ATA DevicesUSB Devices Open FirmwareE F a C E Introduction Features Case and External Features Shows a front view of the computerFront view 2Side view showing I/O bay Compatibility Issues System SoftwareUSB Ports and Devices Main RAM Expansion ModulesVideo RAM Expansion Modules Page Architecture Architecture Backside Cache Processor moduleG3 Microprocessor Controller IC Main Logic BoardMemory Controller and PCI Bridge Built-in Modem USB ControllerVideo Display Subsystem Infrared Link Module Devices and Ports USB Connectors USB PortsTransfer Types Supported GNDUSB Compatibility Issues ADB CompatibilityUSB Storage Devices Serial Port CompatibilityMacintosh-To-Macintosh Connections USB ControllerKeyboard Keyboard LayoutMouse Keyboard and USBHard Disk Drive Video DisplayInfrared Communication Link Sound SystemBuilt-in Microphone Sound InputsSound Outputs External Sound InputHeadphone Jacks Sound SpeciﬁcationsExternal Sound Output Total harmonic distortion Ethernet Port Internal ModemPage RAM Expansion Placing the Computer Face Down Removing the Logic Board AssemblyExpansion Slots Removing the bottom cover Unfastening the CablesRAM Expansion 3Logic board assembly handle and retaining screws Removing the Retaining ScrewsRemoving the Logic Board Assembly Removing the EMI ShieldLocations of the Expansion Slots Main RAM Expansion 6Locations of the RAM expansion slotsMechanical Design of RAM SO-DIMMs Electrical Design of RAM SO-DIMMsSdram Devices Conﬁguration of RAM SO-DIMMs RAM SO-DIMM Electrical Limits Address MultiplexingVideo RAM Expansion Page Software Why Make This Change? What Has Changed Features of the New Approach User Experience PerformanceRAM Footprint Data Structures and FilesBoot ROM Contents Mac OS ndrv Drivers RtasToolbox Image File Contents ToolBox ROM Image NewWorld Boot ProcessTrampoline Code What Is Different Interrupt HandlingOutmoded Resources RAM FootprintNanoKernel Startup Disk Control PanelMachine Identiﬁcation Open Firmware and the Device TreeInterrupt Layout Software Abbreviations Chrp NMI Page Index Nvram X, Y, Z Allen Watson