SR850 Basics

Current Input (I)

The current input on the SR850 uses the A input BNC. Voltage or current input is chosen in the INPUT menu. The current input has a 1 kΩ input impedance and a current gain of either 106 or 108 Volts/Amp. Currents from 1 µA down to 2 fA full scale can be measured.

The impedance of the signal source is the most important factor to consider in deciding between voltage and current measurements.

For high source impedances, greater than 1 MΩ (106 gain) or 100 MΩ (108 gain), and small cur- rents, use the current input. Its relatively low impe- dance greatly reduces the amplitude and phase errors caused by the cable capacitance-source impedance time constant. The cable capacitance should still be kept small to minimize the high fre- quency noise gain of the current preamplifier.

For moderate to low source impedances, or larger currents, the voltage input is preferred. A small value resistor may be used to shunt the signal cur- rent and generate a voltage signal. The lock-in then measures the voltage across the shunt resis- tor. Select the resistor value to keep the shunt volt- age small (so it does not affect the source current) while providing enough signal for the lock-in to measure.

Which current gain should you use? The current gain determines the input current noise of the lock- in as well as its measurement bandwidth. Signals far above the input bandwidth are attenuated by 6 dB/oct. The noise and bandwidth are listed below.

Gain

Noise

Bandwidth

106

130 fA/√Hz

70 kHz

108

13 fA/√Hz

700 Hz

AC vs DC Coupling

The signal input can be either AC or DC coupled. The AC coupling high pass filter passes signals above 160 mHz (0.16 Hz) and attenuates signals at lower frequencies. AC coupling should be used at frequencies above 50 mHz whenever possible. At lower frequencies, DC coupling is required.

A DC signal, if not removed by the AC coupling filter, will multiply with the reference sine wave and produce an output at the reference frequency. This signal is not normally present and needs to be removed by the low pass filter. If the DC compo- nent of the signal is large, then this output will be large and require a long time constant to remove. AC coupling removes the DC component of the signal without any sacrifice in signal as long as the frequency is above 160 mHz.

The current input current to voltage preamplifier is always DC coupled. AC coupling can be selected following the current preamplifier to remove any DC current signal.

The current gain is selected in the INPUT menu when the I input is in use.

3-22

Page 75 Page 77
Page 76
Image 76
SRS Labs SR850 manual Current Input, AC vs DC Coupling
Page 75 Page 77

SR850 specifications

The SRS Labs SR850 is a high-performance audio processor designed to enhance the listening experience across a variety of applications. With its advanced technologies, the SR850 delivers superior sound quality that is particularly noticeable in environments where audio clarity and fidelity are paramount. This device caters to audio professionals, audiophiles, and casual listeners who demand exceptional performance from their audio systems.

One of the standout features of the SR850 is its proprietary SRS 3D Audio technology. This innovative feature creates a more immersive soundstage, allowing users to experience audio as if they were in a live performance setting. By adding depth and dimension, it elevates the listening experience, making music, movies, and games far more engaging.

Additionally, the SR850 incorporates SRS dialog clarity technology, which enhances speech intelligibility in dialogues and vocals. This is particularly beneficial in film and television viewing, where dialogue can sometimes be drowned out by background music or sound effects. With dialog clarity, users can enjoy crystal-clear conversation tracks without adjusting volume levels continuously.

The device also supports various audio formats, ensuring compatibility with a broad range of media. It boasts inputs for both digital and analog sources, allowing connections to various devices such as TVs, laptops, gaming consoles, and more. The versatility of inputs makes the SR850 a convenient addition to any home entertainment system.

Another impressive characteristic of the SR850 is its compact and user-friendly design. The intuitive interface makes it easy for users to adjust settings to their preference, whether they are a novice or an audio expert. The device is equipped with programmable presets, enabling users to store their favorite sound profiles, making switching between settings quick and hassle-free.

Furthermore, the SR850 features advanced EQ capabilities, granting users the ability to tailor the audio output to their specific tastes. This personalized approach to sound adjustment enhances the overall experience, allowing users to get the most out of their audio content.

In summary, the SRS Labs SR850 is a sophisticated audio processor packed with features designed to significantly uplift sound quality and listening pleasure. With its cutting-edge technologies such as SRS 3D Audio and dialog clarity, an array of connectivity options, and customizable EQ settings, the SR850 stands out as an outstanding option for anyone looking to enhance their audio experience. Whether for professional use in sound engineering or personal enjoyment in home entertainment, the SR850 proves to be a valuable asset.
Top Page Image Contents