High-quality preamplifier

The circuit illustrated in Figure 3-10 is a multi-function input configuration that includes a preamplifier. It features several input types, including a tuner input, a magnetic tape playback input, a magnetic phono input, and a phono equalizer input. The input amplifier is designed using a dual operational amplifier, specifically the LT1057, which facilitates a zoom function. The circuit incorporates a dedicated phono input equalization circuit for electromagnetic pickups, and an additional circuit for selecting various multi-function inputs. A switch is utilized to select different inputs, including an equalized amplifying input for recording. The circuit also includes functionality for tape playback and recording monitoring. The LT1057 dual op-amp serves as a high-speed precision operational amplifier, utilizing a JFET input stage. It has a slew rate of 13 V/μs and an input noise voltage of 2.1 μV. Alternative op-amps such as the LT1058, LT1037, LT1028, or NE5532 can also be employed in this configuration.

The circuit operates as a versatile input stage for audio applications, allowing for seamless integration of multiple audio sources. The preamplifier stage is critical for boosting low-level signals from sources like magnetic phono cartridges, which typically produce weak output levels. The LT1057, known for its low noise and high-speed performance, ensures that the integrity of the audio signal is maintained throughout the amplification process.

The dedicated phono equalization circuit is essential for compensating the frequency response of vinyl records, which are recorded with a specific equalization curve (RIAA). This equalization allows for accurate playback of the recorded audio. The input selection switch enables the user to choose between various sources, enhancing the circuit's flexibility for different audio setups. The inclusion of tape playback and monitoring functions is particularly beneficial for recording applications, allowing users to monitor the audio signal being recorded in real-time.

The circuit's design can accommodate various operational amplifiers, providing options for customization based on performance requirements or availability. The use of JFET inputs in the op-amp configuration minimizes distortion and improves the overall sound quality. This multi-function input circuit is suitable for high-fidelity audio systems, providing a robust solution for signal management and amplification in professional audio environments. Circuit shown in Figure 3-10. This is a multi-function input with a preamplifier, including the tuner input, a magnetic tape playback input, magnetic phono input and phono equa lizer input functions. Input amplifier consists of a whole integrated dual op amp LT1057 input as a zoom function, where 1/21C dedicated phono input equalization circuit for the electromagnetic, and the remaining 1/21C for multi-function input selection switch circuit o SAt used to select different inputs, including equalized amplifying input record into. What the carp are used to select the tape playback and recording monitor. LT1057 dual op amp input stage of high-speed precision op amp by a JFET as difference, its conversion rate of 13V /, ls, input noise voltage 2.lpLVn, o can be LT1058, LT1037, LT1028, can also be used NE5532 etc.