A thread to discuss this Phono preamp.
The frequency response of the corrector in the high-frequency region is formed using a high-pass filter with a given time constant τ1 = L / R. the function of resistance R is performed by the dynamic resistance of the JFET transistor VT1, which is also an amplifying element of the circuit. The value of L is given by the inductor.
The input stage operates as a source follower VT3 with a transformer load. The low output impedance of the follower and the high quiescent current of the stage significantly reduces the requirements for the transformer and increases the accuracy of calculating the correction circuits L1, R2 and R3, which determine the time constants of 3180 μS and 318 μS.
The repeater DC operating modes are set by the current source on transistors VT4, VT5. The current source is shunted with a C10 capacitance. The disadvantage of this solution is that the signal current flows through the capacitor. The advantage of this solution is that the signal current flows through the capacitor, and the parasitic parameters and nonlinearities of the current source do not affect the signal.
The frequency response of the corrector in the high-frequency region is formed using a high-pass filter with a given time constant τ1 = L / R. the function of resistance R is performed by the dynamic resistance of the JFET transistor VT1, which is also an amplifying element of the circuit. The value of L is given by the inductor.
The input stage operates as a source follower VT3 with a transformer load. The low output impedance of the follower and the high quiescent current of the stage significantly reduces the requirements for the transformer and increases the accuracy of calculating the correction circuits L1, R2 and R3, which determine the time constants of 3180 μS and 318 μS.
The repeater DC operating modes are set by the current source on transistors VT4, VT5. The current source is shunted with a C10 capacitance. The disadvantage of this solution is that the signal current flows through the capacitor. The advantage of this solution is that the signal current flows through the capacitor, and the parasitic parameters and nonlinearities of the current source do not affect the signal.
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