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A RIAA phono preamplifier is an essential component in turntable audio systems. Its primary purpose is to amplify the weak signal generated by a turntable’s cartridge and apply the RIAA (Recording Industry Association of America) equalization curve to restore the original sound balance of vinyl records. Below, we delve into the key aspects of such a preamplifier and the use of the SGM3204 IC for creating a symmetrical power supply.
Schematic Circuit RIAA Phono preamplifier with NJM4580
What is a RIAA Phono Preamplifier?
A RIAA phono preamplifier serves two critical functions:
- Amplification: Turntable cartridges produce very low-level signals (in the millivolt range). A phono preamp amplifies this signal to line level (around 0.3 volts), which is suitable for further processing by amplifiers or audio systems.
- RIAA Equalization: During vinyl mastering, bass frequencies are reduced, and treble frequencies are boosted to optimize groove spacing and reduce noise. The RIAA preamp reverses this process during playback, restoring the original frequency balance.
- Without a RIAA preamp, the audio output would be weak and have an unnatural frequency response, making it essential for high-quality vinyl playback.
Importance of Using a RIAA Preamp with Turntables
- Sound Quality: A well-designed preamp ensures accurate reproduction of the original recording, preserving details, warmth, and dynamic range.
- Compatibility: Modern audio systems often lack built-in phono stages, making an external RIAA preamp necessary for connecting turntables.
- Standardization: The RIAA curve provides a universal standard, ensuring consistent playback across different audio systems.
Using the NJM4580 in a RIAA Preamp
The NJM4580 operational amplifier can be used in RIAA preamplifiers due to its low noise and high-performance characteristics. It enables precise amplification and equalization of the phono signal, ensuring fidelity and minimal distortion.
Using the SGM3204 for a Symmetrical Power Supply
The SGM3204 is a charge pump voltage inverter IC that can generate a negative voltage from a positive input voltage. It is ideal for creating symmetrical power supplies needed in circuits like RIAA preamps that use operational amplifiers requiring both positive and negative voltages.
Key Features of SGM3204
- Input voltage range: 1.4V to 5.5V
- Output current: Up to 200mA
- Efficiency: Over 80%
- Compact design with minimal external components.
Application in Symmetrical Power Supply
By combining the SGM3204 with a positive voltage regulator (e.g., 7805), you can create symmetrical ±5V or ±12V power supplies. This configuration ensures proper operation of operational amplifiers in audio circuits by providing both positive and negative rails.
In summary, a RIAA phono preamplifier is indispensable for vinyl playback due to its amplification and equalization functions. The NJM4580 offers excellent performance for such applications, while the SGM3204 simplifies the creation of symmetrical power supplies, making it an efficient choice for powering audio circuits.
There is a point marked on the PCB as GND; a wire must be connected to the GND in the phonograph board.
BOM Circuit RIAA Phono preamplifier with NJM4580
Last update: 02/05/2025 12:54
| Componente | Valor | Descrição | Quantidade |
|---|---|---|---|
| Resistors | |||
| R1, R2, R17, R18 | 330 (331) | R0603 – SMD resistor | 4 |
| R3, R4, R6, R7, R15, R16 | 100k (104) | R0603 – SMD resistor | 6 |
| R5 | 220 (221) | R0603 – SMD resistor | 1 |
| R8, R9 | 820 (821) | R0603 – SMD resistor | 2 |
| R10 | 10k (103) | R0603 – SMD resistor | 1 |
| R11, R12 | 560k (564) | R0603 – SMD resistor | 2 |
| R13, R14 | 47k (473) | R0603 – SMD resistor | 2 |
| Capacitors | |||
| C1, C3, C20, C22, C23 | 100n | C0603 – SMD ceramic capacitor | 5 |
| C2 | 2200uF/25V | Capacitor eletrolítico | 1 |
| C4, C5, C9, C10 | 220p | C0603 – SMD ceramic capacitor | 4 |
| C6, C21 | 2200uF/12V | Electrolytic Capacitor | 2 |
| C7, C8, C18, C19 | 10uF | SMD Electrolytic Capacitor 5×5,3 | 4 |
| C11, C12 | 47uF | SMD Electrolytic Capacitor 5×5,3 | 2 |
| C13, C14 | 2.2n | C0603 – SMD ceramic capacitor | 2 |
| C15, C16 | 8.2n | C0603 – SMD ceramic capacitor | 2 |
| C17 | 10u | C0805 – SMD ceramic capacitor | 1 |
| Semiconductors | |||
| IC1 | NJM4580L | SIP8 – Dual Op amp | 1 |
| IC2 | SGM3204 | SGM3204 Unregulated 200mA Charge Pump Voltage Inverter | 1 |
| IC3 | LM78M05ABDT-TR | 500mA Fixed 5V Positive electrode 35V TO-252-2(DPAK) Voltage Regulators – Linear, Low Drop Out (LDO) |
1 |
| B1 | DB107S | Bridge rectifier | 1 |
| LED1 | LED 0603 | LED0603 – Red LED | 1 |
| Miscellaneous | |||
| CN1 | IN | XH 2.54mm 3-pin connector | 1 |
| J1 | power | Terminal block 3 pin 5,08 mm | 1 |
| CN2 | OUT | XH 2.54mm 3-pin connector | 1 |
| Soldering, Wires, PCB, Box, Power Supply | |||
Download PCB Gerber + BOM + Centroid File + PDF + PNG
- PDF Datasheet PDF IC NJM4580L
- PDF Datasheet PDF IC SGM3204
- DPDF Datasheet PDF IC Lm78M05
- PDF Datasheet PDF DB107S
