OPERATING INSTRUCTIONS

The SR552 Voltage Pre-Amplifier is designed to be used with either the SR510/530 lock-ins as well as the newer DSP lock-ins. The SR552 reduces the input noise and extends the full scale sensitivity to 10 nV (without expand). When used as a remote pre-amplifier, the SR552 can eliminate the effects of noise pickup on long signal cables.

Power and control are supplied to the SR552 via the 9 pin cable which is supplied with the unit. Attach one end of the cable to the connector on the rear of the SR552. With the lock-in power off, connect the other end of the cable to the PRE-AMP connector on the rear of lock-in. Both ends of the cable are equivalent. If a longer cable is required, any standard 9 pin cable will suffice since all connections are straight through. When the lock-in power is on, the POWER indicator on the SR552 will light.

CONNECTING THE SR552

The (A) Output of the SR552 should be connected to the (A) Input of the lock-in. For most applications, this single connection will be adequate. The lock-in Input Selector should be set to (A). For situations where there may be noise pick-up on this cable, it is better to connect the SR552 (B) Output (shielded pre-amp ground) to the (B) Input of the lock-in as well. The (A) and (B) cables should be twisted together to prevent inductive pick-up. The lock- in Input Selector should then be set to (A-B).

The SR552 (A) and (B) Inputs should now be used as the lock-in voltage inputs. The input switch selects single ended, (A), or differential, (A-B), operation. The input impedance is 100 kΩ , 25 pF. The connector shields are isolated from the chassis ground by 10 Ohms. These inputs are protected to 100 Vdc but the ac input should never exceed 10 V peak. The maximum input before overload is 70 mV rms. The OVERLOAD indicator will light whenever the pre-amplifier overloads. Note that overloads that occur after the pre-amplifier are indicated by the lock-in's overload indicator.

USING THE SR550 WITH THE SR510/530 The SR510/530 lock-ins sense the presence of the SR552 through the power cable and takes it into account when setting the gain of its own amplifiers. Thus, to obtain the correct overall gain, the SR552 output must be connected to the voltage inputs of the lock-in.

The overall sensitivity of the lock-in plus the pre- amplifier is displayed as the sensitivity on the lock-in front panel. It is necessary to divide the displayed sensitivity by 10.

The gain of the SR552 is 10, 20, 50, or 100. The gain is controlled by the lock-in and is set to maximize the pre-amplifier gain while maintaining the selected dynamic reserve. For most sensitivities, the pre-amplifier gain will be

100.The following table summarizes the gain allocation.

SR552 Pre-Amplifier Front Panel and Rear Panel

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SRS Labs Voltage Pre-amplifier, SR550/552 manual Connecting the SR552
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SR550/552, Voltage Pre-amplifier specifications

SRS Labs, a renowned leader in audio technology, has made significant strides in the realm of audio amplification with the Voltage Pre-amplifier models SR550 and SR552. These pre-amplifiers are designed to deliver exceptional performance and fidelity, appealing to both professional and home audio enthusiasts.

The SR550 and SR552 are equipped with a host of features that ensure high-quality sound reproduction. They utilize state-of-the-art components and engineering techniques to minimize distortion and maintain signal integrity. One of the defining characteristics of the SR series is their low noise performance. The pre-amplifiers are designed with precision circuitry that effectively reduces background noise, allowing for a cleaner audio signal that is crucial for critical listening applications.

A key feature of the SR550 and SR552 is their adjustable gain settings. This allows users to fine-tune the amplification levels to match different sources and listening environments. Whether you are connecting a low-output microphone or a high-level line source, the adjustable gain ensures optimal performance across various setups.

Both models also support a wide frequency response range, making them suitable for a variety of audio applications, from studio recordings to live sound reinforcement. The frequency response extends well beyond the human hearing range, which ensures that even the most subtle details in recordings are faithfully reproduced.

In terms of connectivity, the SR550 and SR552 offer a range of input and output options. Users can connect various audio sources through XLR and TRS inputs, while balanced outputs maintain the integrity of the audio signal during transmission. This versatility makes them ideal for integration into existing audio systems.

Another notable technology featured in the SR series is SRS Labs’ proprietary noise reduction technology. This feature actively reduces unwanted background noise without compromising the audio clarity, providing a more immersive listening experience.

Durability is another hallmark of the SR550 and SR552, with robust construction and high-quality materials designed to withstand the rigors of regular use in both studio and live environments.

In conclusion, the SRS Labs Voltage Pre-amplifiers SR550 and SR552 stand out in the market for their exceptional sound quality, innovative features, and reliable performance. Whether for critical studio editing or live audio applications, these pre-amplifiers are engineered to meet the needs of audiophiles and professionals alike, ensuring an unparalleled listening experience.
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