SRS Labs SR560 manual Appendix B, Noise Sources and Cures, Intrinsic Noise Sources

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APPENDIX B

NOISE SOURCES AND CURES

Noise, random and uncorrelated fluctuations of electronic signals, finds its way into experiments in a variety of ways. Good laboratory practice can reduce noise sources to a manageable level, and the lock-in technique can be used to recover signals, which may still be buried in noise.

Intrinsic Noise Sources

Johnson Noise

Arising from fluctuations of electron density in a resistor at finite temperature, these fluctuations give rise to a mean square noise voltage,

_

V2 = ∫4kT Re [Z(f)]df = 4 kTR∆f

where k = Boltzmann’s constant,

1.38x 10–23J/°K; T is the absolute temperature in Kelvin; the real part of the impedance, Re[z(f)] is the resistance R; and we are looking at the noise source with a detector, or AC voltmeter, with a bandwidth of ∆f in Hz. For a 1 MΩ resistor:

_

(V2) 1/2 = 0.13µV/√Hz

To obtain the rms noise voltage that you would see across this 1MΩ resistor, we multiply 0.3 µV/√Hz by the square root of the detector bandwidth. If, for example, we were looking at all frequencies between DC and 1 MHz, we would expect to see a rms Johnson noise of:

_

(V2) 1/2 = 0.13µV/√Hz * (106 Hz) 1/2 = 130 µV

‘1/f Noise’

Arising from resistance fluctuations in a current carrying resistor, the mean squared noise voltage due to ‘1/f ‘noise is given by,

_

V2 = AR2I2 ∆f/f

where A is a dimensionless constant, 10-11

for carbon, R is the resistance, I the current, the bandwidth of our detector, and f is the frequency to which the detector is tuned. For a carbon resistor carrying 10 mA with R = 1 k, ∆f = f = 1 Hz, we have:

Vnoise= 3µVrms

Others

Other noise sources include flicker noise found in vacuum tubes, and generation and recombination noise found in semiconductors.

All of these noise sources are incoherent. Thus, the total noise is the square root of the sum of the squares of all the incoherent noise sources.

Non-Essential Noise Sources

In addition to the “intrinsic” noise sources listed above there are a variety of “non- essential” noise sources, (i.e. those noise sources which can be minimized with good laboratory practice). It is worthwhile to look at what might be a typical noise spectrum encountered in the laboratory environment:

Noise Spectrum

Some of the non-essential noise sources appear in this spectrum as spikes on the intrinsic background. There are several

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Contents Model SR560 Page Table of Contents Calibration and Repair PCB SR560 Revision F 9/89 SchematicsAppendix a Appendix BInstrument Overview Introduction and SetupPreparation for USE Repackaging for Shipment Accessories FurnishedUse in Biomedical Applications Environmental ConditionsPage SR560 LOW-NOISE Preamplifier Specifications Chart SpecificationsSpecifications Operation and Controls PowerFront Panel Operating Summary SourceFilters Reset Gain ModeGain OutputAmplifier Power Output AC Power InputBattery Charger Rear Panel Operating SummaryBattery Care Battery Care and UsageBlanking Input RS-232 InterfaceAvoid Deep Discharge Circuit Description Configurable Filters and GainDifferential LOW-NOISE Front END Output StagesMicroprocessor Battery Charger and PRE-REGULATORSOverload Detection Rear Panel Interfaces Power RegulatorsFront Panel Batteries and P.E.MFront END Replacement Offset AdjustmentCalibration and Repair CalibrationFuse Replacement SR560 Offset Adjustment ProcedureBattery Replacement Noise Contours Dynamic Reserve Input Voltage NoiseMaximum Calibration and Repair Appendix a CommandsRemote Programming IntroductionAppendix a Noise Sources and Cures Appendix BIntrinsic Noise Sources Non-Essential Noise SourcesInductive Coupling Capacitive CouplingThermocouple Effect Resistive Coupling or ‘Ground Loops’Microphonics Appendix B Front Panel Parts List SR560 Component Parts ListMain Board Parts List 22U MIN 01U Axial 804 00225-548 Insl MTP5N05 SR560 Component Parts List SR560 Component Parts List PIN Mach SR566 Assy Adhes Tape Miscellaneous Parts List SR560 Component Parts List

SR560 specifications

SRS Labs SR560 is a cutting-edge audio enhancement technology that has gained recognition for its ability to deliver an immersive sound experience. Built upon years of research, the SR560 utilizes proprietary algorithms to achieve high-fidelity sound output while maintaining an incredibly dynamic range.

One of the most notable features of the SR560 is its adaptive audio processing, which adjusts sound dynamics based on the content being played. This means that whether one is listening to music, watching a movie, or playing video games, the sound quality is optimized in real-time to provide the best listening experience. The SR560 excels at enhancing dialogue clarity in films, ensuring that important audio elements are never lost amidst background sounds.

Another key characteristic of the SR560 is its support for multi-channel audio. With the rise of surround sound systems, the SR560 is designed to integrate seamlessly with 5.1 and 7.1 speaker setups. This ensures that users can enjoy a true surround sound experience, where each audio channel is processed independently to create a lifelike auditory environment. The SR560’s processing capabilities allow it to convert standard stereo audio into multi-channel output, enriching the listening experience for any audio format.

SRS Labs has equipped the SR560 with advanced bass optimization technology. This feature enhances low-frequency sound, providing deep, rich bass without distortion. Whether it’s the thumping beats of music or the rumble of action-packed movies, the SR560 ensures that users can experience the full spectrum of audio without compromising on quality.

Furthermore, the SR560 showcases state-of-the-art sound management features that provide users with customizable audio profiles. This allows users to tailor their audio experience according to personal preferences, whether they prefer a more balanced sound, enhanced bass, or boosted treble frequencies. The intuitive interface ensures that adjustments can be made effortlessly.

In conclusion, the SRS Labs SR560 stands out as a versatile audio enhancement technology that caters to the needs of various audio consumers. By combining adaptive processing, multi-channel support, bass optimization, and customizable profiles, the SR560 ensures a rich and immersive audio experience. As the demand for high-quality sound continues to rise, the SR560 is poised to remain a significant player in the evolution of audio technology.
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