A two-transistor phono MC step-up offers lower noise than a one-transistor model. This MC step-up uses two PNP transistors and can be powered from a 12V battery (or other clean/regulated 12V power source). Charge the battery when the amplifier is not in use. The value of R4 depends on the hfe of the transistor used (Table 1).
Distortion of the amplifier is low due to local feedback. The gain of the amplifier is 19-20dB.
above: FIG. 1: Two-transistor preamp circuit.
above: FIG. 2: Pinouts for the different transistors. Bottom view.
Components:
- C1=22uF
- C2, C3=1 uF polypropylene
- R1=120 ohm wirewound
- R5, R6=1200ohm
- L=22nH
TABLE 1:
Transistors==R4==hfe==Relative Noise
BC 878 Siemens ==68k ==120 ==32
BC 880 Siemens ==68k ==120 ==33
BC636 Motorola ==100k ==190 ==58
BC 640 Motorola ==56k ==90 ==65
MPSA 56 National ==82k ==150 ==66
BC 636 Siemens ==56k ==100 ==75
BC 369 Philips ==200k ==360 ==98
MPSA 56 Fairchild ==100k ==180 ==100
2N4403 Motorola ==120k ==200 ==101
BC 640 Philips ==91k ==160 ==114
2SA 970 Toshiba ==270k ==450 ==117
BC 212B ON Semiconductor ==180k ==300 ==121
2N5401 Philips ==100k ==190 ==125
BC 638 Philips ==75k ==140 ==126
2N3906 Philips ==100k ==190 ==146
2N3799 Motorola ==220k ==400 ==155