RIAA Preamplifier Utilising BC547
This RIAA preamplifier circuit for magnetic cartridges uses a pair of BC547 transistors and has minimal component count. The circuit has excellent sound quality, and exhibits good stability for a wide range of magnetic cartridges. An advantage of this circuit is that the transistors are cheap and readily available, and the circuit operates on +26 V single rail, hence it can be installed into a power amplifier that may already have comparable power supply rails.
Board Layout
The circuit is symmetrical, with components nicely spaced out; hence it will be very simple to build. Ideally, installing the components for both channels at the same time could make the build easier and quicker. Notice how the transistors for the two channels face in opposite directions.
Component List
| Type | Part Number | Value | Description |
| Resistors | R1 | 1 kΩ | Metal-film, 1/4-watt, 1 % |
| R2 | 100 kΩ | Metal-film, 1/4-watt, 1 % | |
| R3 | 220 kΩ | Metal-film, 1/4-watt, 1 % | |
| R4 | 8.2 kΩ | Metal-film, 1/4-watt, 1 % | |
| R5 | 470 Ω | Metal-film, 1/4-watt, 1 % | |
| R6 | 330 Ω | Metal-film, 1/4-watt, 1 % | |
| R7 | 100 kΩ | Metal-film, 1/4-watt, 1 % | |
| R8 | 27 kΩ | Metal-film, 1/4-watt, 1 % | |
| R9 | 390 kΩ | Metal-film, 1/4-watt, 1 % | |
| R10 | 220 Ω | Metal-film, 1/2-watt, 1 % | |
| R11 | 150 kΩ | Metal-film, 1/4-watt, 1 % | |
| Capacitors | C1 | 1 µF | 50 V, Electrolytic |
| C2 | 470 pF | Ceramic Disc | |
| C3 | 100 pF | Ceramic Disc | |
| C4 | 100 µF | 10 V, Electrolytic | |
| C5 | 10 µF | 35 V, Electrolytic | |
| C6 | 220 µF | 35 V, Electrolytic | |
| C7 | 2.7 nF | Mylar, Polyester Film | |
| C8 | 10 nF | Mylar, Polyester Film | |
| Semiconductors | TR1, TR2 | BC547 | PDIP |
| Misc | Stripboard | 36-strips × 50-holes | 95 mm × 127 mm |
For the capacitors, 5 % tolerance is preferable and 10 % as a second choice.
Board Links
Board Cuts
