The Stanford Research Systems SR560 Low-Noise Voltage Preamplifier is a high-performance preamplifier that is ideal for a wide range of applications including low temperature measurements, optical detection, and audio engineering. The SR560 has a differential front-end with 4 nV/√Hz input noise and an input impedance of 100 MΩ. Complete noise figure contours are shown in the SR560 Tech Note at the end of this section. The SR560’s inputs are fully floating (BNC shields are not connected to chassis ground). Both the amplifier ground and the chassis ground are available on the rear panel for flexibility in grounding the instrument. Input offset nulling is accomplished by a front-panel potentiometer, accessible with a small screwdriver. In addition to the signal inputs, a rear-panel TTL blanking input lets you quickly turn off and on the instrument’s gain. This is useful in preventing front-end overloading. The gain turns off 5 μs after the TTL level goes high, and back on again within 10 μs after the TTL signal goes low.