High Impedance Preamplifier (CB941E)

This very high input impedance preamplifier is from a publication of 1977 but can also be mounted with the BF245 or MPF102 for TR1 and TR2 to BC548. Changes made from the original circuit allow the use of these most current components. The operational amplifier is still common and can be used equivalent type. The circuit has a 2.2 M ohm input impedance and good gain given by the ratio of R6 to R7. With the gain most audio amplifiers can be driven easily. The circuit has very low power consumption and can be powered by battery. If power supply is used, must have excellent filtering, to prevent any noise. Input and output signal cables must be shielded. Two units powered by a single source must be mounted for a stereo version.




Circuit Bench