Phono RIAA Preamplifier

  
In this circuit exists a second designing proposal of preamplifier RIAA. The first stage uses discernible components and in second exist a opamp. [IC1]. In the negative feedback exist the correction RIAA filters. Certain points need certain discriminators: 1] capacitors C2 and C15, will be supposed to suit with the cartridge characteristics that you will use. 2] Transistors Q1-2 and Q8-9, good is they have matched in their characteristics and they are found very near so that they have the same thermic behavior. This can become with choice from a lot of transistors so that we find certain pairs with same characteristics, measuring with a hfe meter. 3] the trjmmer TR1-2 regulate the characteristics of differential amplifiers in the input, for null of DC voltage in the exit of stage. 4] the capacitors C4-17 and C11-24 should matched between them with capacitance meter, so that they have the same values, avoiding in this way the purchase of precise capacitors. 5] All the resistors should be metal film 1%. the circuit supply become from power supply, that exist already in amplifier or from external good stabilised supply ± 15V 100mA.
Phono RIAA Preamplifier - schematic




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