Table of Contents
LM1875 amplifier board LM1875 A 2.1 channel amplifier board composed of LM1875 + NE5532, with the left and right channels as forward amplification circuits and the subwoofer as BTL output. It uses a point-to-ground method, and due to space constraints, it needs to be used with a power filtering board.
Absolutely HIFI! The PCB board effect is as follows! Pursuing HIFI quality, creating outstanding engineering! After making it with LM1875 and other components, you can enjoy the ultimate HIFI experience.
Multiple hole positions are reserved for coupling capacitors to meet different needs. It also controls the input source through an Omron relay to achieve smooth sound switching.
The vocals are very clear and natural, not like squeezed out sound, very clear, making you feel like you are there!
If you want to DIY a desktop mini amplifier of your own, this will be the best choice! Pair it with a speaker protection board you made yourself for safety and HIFI!
Schematic LM1875 + NE5532 2.1 power amplifier subwoofer
For the voltage of the amplifier board, it seems that ±15V part is more suitable, it can be smaller, and the ±25V part can also be changed, as long as it is suitable for the voltage of LM1875. I just followed this completely, and all parts are working normally! Have a good time, everyone!
I will attach the circuit of the power board and equalizer board I use… nothing special, especially the power board, I feel like the design I made is a little too fancy. Here is a demonstration video after completion (not sure if the subwoofer can be recorded).
About IC Lm1875
The LM1875 is a high-performance audio amplifier integrated circuit (IC) that is commonly used in audio amplifier applications. It is a monolithic power amplifier designed to deliver high-quality audio reproduction with a low level of distortion. The LM1875 is capable of delivering up to 20 watts of power into an 8-ohm load, making it suitable for use in a wide range of audio systems. This IC features a high signal-to-noise ratio, wide bandwidth, and low total harmonic distortion, making it a popular choice for audio enthusiasts and professionals alike. With its compact size and easy-to-use design, the LM1875 is a versatile and reliable option for audio amplifier projects.
About IC NE5532
The NE5532 is a dual operational amplifier that is commonly used in audio applications due to its high performance and low noise characteristics. It features a wide bandwidth, low distortion, and high slew rate, making it ideal for audio signal processing and amplification. The NE5532 is popular among audio enthusiasts and professionals for its ability to deliver clean and clear sound reproduction. Its versatile design allows for various configurations, such as inverting and non-inverting amplifiers, filters, and mixers. Overall, the NE5532 is a reliable and high-quality integrated circuit that is widely used in the audio industry.
About IC LM337
The LM337 is a versatile negative voltage regulator IC that is commonly used in electronic circuits to provide a stable and adjustable negative voltage output. It is a member of the LM317 family of voltage regulators, but with a negative output voltage capability. The LM337 can provide an output voltage range from -1.2V to -37V with a maximum output current of 1.5A. It has built-in thermal overload protection and short circuit protection, making it a reliable and safe choice for regulating negative voltages in various applications. The LM337 is widely used in power supplies, battery chargers, audio amplifiers, and other electronic devices where a stable negative voltage source is required.
About IC LM317
The LM317 is a versatile and widely used integrated circuit that serves as an adjustable voltage regulator. It is commonly used in electronic circuits to provide a stable and adjustable output voltage, making it an essential component in many power supply designs. The LM317 is capable of regulating output voltages from 1.25 volts up to 37 volts, making it suitable for a wide range of applications. Its adjustable output voltage makes it useful for powering a variety of electronic devices and components. With its simple design and reliable performance, the LM317 is a popular choice for hobbyists and professionals alike in the field of electronics.
BOM Amplifier
| Parts | Value | Description | Quantity |
| Resistors | |||
| R1,R3,R6,R8,R10,R12,R33,R35,R36 | 22K | Red, red, black, red, brown | 9 |
| R2,R7,R19,R24 | 1K | Brown, black, black, brown, brown | 4 |
| R4,R5,R9,R32 | 1 Ohm 1/2W | Brown, black, black, silver, brown | 4 |
| R11,R34 | 680 | Blue, gray, black, black, brown | 2 |
| R13,R18 | 22K | Red, red, black, red, brown | 2 |
| R14,R17 | 100K | Brown, black, black, orange, brown | 2 |
| R15,R16 | 47K | Yellow, violet, black, red, brown | 2 |
| R20,R23,R27,R28 | 5.1K | Green, brown, black, brown, brown | 4 |
| R25,R26 | 10K | Brown, black, black, red, brown | 2 |
| R29 | 33K | Orange, orange, black, red, brown | 1 |
| R30,R31 | 10K | Brown, black, black, red, brown | 2 |
| Capacitors | |||
| C1,C2 | Coupled capacitor | 2.2UF/250V Film capacitor | 2 |
| C4,C7,C9,C10,C12,C15,C18,C28,C30,C34,C36,C39 | 100n (104) | Ceramic capacitor | 12 |
| C5,C6,C13,C14,C37,C38 | 100uF/35V | Electrolytic capacitor | 6 |
| C8,C11 | 22uF/35V | Electrolytic capacitor | 2 |
| C16,C33 | 23n (223) | Film capacitor | 2 |
| C17,C19 | 220uF/35V | Electrolytic capacitor | 2 |
| C24,C27 | 2,2n (222) | Film capacitor | 2 |
| C26,C35 | 100n (104) | Film capacitor | 2 |
| C29,C32 | 10uF/35V | Electrolytic capacitor | 2 |
| C31 | 220n (224) | Film capacitor | 1 |
| CN1 | POWER | CONN-TH_1755749 | 1 |
| CN2 | POWER | CONN-TH_1755736 | 1 |
| Semiconductors | |||
| U1,U2,U3,U6 | LM1875 | TO-220-5 audio power amplifier | 4 |
| U4,U5 | NE5532 | DIP-8 Dual op-amp | 2 |
| Miscellaneous | |||
| CN1 | POWER | CONN-TH_1755749 | 1 |
| CN2 | POWER | CONN-TH_1755736 | 1 |
| H1,H2 | AUDIO | HDR-F-2.54_1X3 – Pin header | 2 |
| H3 | 12V | HDR-F-2.54_1X2 – Pin header | 1 |
| H4 | Potentiometer out | HDR-F-2.54_1X3 – Pin header | 1 |
| H5 | Potentiometer in | HDR-F-2.54_1X3 – Pin header | 1 |
| H6 | R-OUT | HDR-F-2.54_1X2 – Pin header | 1 |
| H7 | L-OUT | HDR-F-2.54_1X2 – Pin header | 1 |
| H8 | BASS-OUT | HDR-F-2.54_1X2 – Pin header | 1 |
| H9 | Potentiometer H-1 | HDR-F-2.54_1X3 – Pin header | 1 |
| H10 | Potentiometer H-2 | HDR-F-2.54_1X3 – Pin header | 1 |
| H11 | Potentiometer L | HDR-F-2.54_1X3 – Pin header | 1 |
| K1 | Relay | G2R-2-24DC | 1 |
| TP1,TP2,TP3,TP4 | M3 | M3 | 4 |
BOM Power supply
| Parts | Value | Description | Quantity |
| +30 | +30 | DO-201_BD5.3-L9.5-P13.50-D1.4-RD | 1 |
| -30 | -30 | DO-201_BD5.3-L9.5-P13.50-D1.4-RD | 1 |
| Capacitors | |||
| C1,C2,C3,C4,C17,C18,C19,C20 | 100n (104) | Ceramic capacitor | 8 |
| C5,C6 | 33p (330) | Ceramic capacitor | 2 |
| C7,C8,C15,C16,C29,C30 | 100n (104) | Ceramic capacitor | 6 |
| C9,C10 | 10000uF/35V | CAP-TH_BD25.0-P10.00-D2.3-FD | 2 |
| C11,C12 | 47uF/35V | CAP-TH_BD6.3-P2.50-D1.0-FD | 2 |
| C13,C14,C31,C32 | 220uF/35V | CAP-TH_BD10.0-P5.00-D1.0-FD | 4 |
| C21,C22 | 3300uF/35V | CAP-TH_BD16.0-P7.50-D1.2-FD | 2 |
| C23,C24 | 330n (334) | Ceramic capacitor | 2 |
| C25,C26 | 10uF/35V | CAP-TH_BD5.0-P2.00-D0.8-FD | 2 |
| CN1 | OUT | CONN-TH_1755736 | 1 |
| D1,D2,D3,D4,D9,D10,D11,D12 | 1N5408G | DO-201 – Diode | 8 |
| D5,D6,D7,D8,D13,D14 | 1N4007 | DO-41 General use diode | 6 |
| Miscellaneous | |||
| HS1,HS2 | HS-35*12*25 | Heat Sink | 2 |
| LED1,LED2 | HDR-F-2.54_1x2 | HDR-F-2.54_1×2 – Pin header | 2 |
| OUT | 1755749 | CONN-TH_1755749 | 1 |
| Resistors | |||
| R1,R2 | 200 | Red, black, black, black, brown | 2 |
| R3,R4 | 5K | Trimpot | 2 |
| R5 | 51K | Green, brown, black, red, brown | 1 |
| R6,R7 | 10K | Brown, black, black, red, brown | 2 |
| R8,R9, R10 | 33K | Orange, orange, black, red, brown | 3 |
| Semiconductors | |||
| U1,U2 | IN | CONN-TH_3P-P9.50_DBT50G-9.5-3P | 2 |
| U3 | LM317 | TO-220-3 – Adjustable positive voltage regulator | 1 |
| U4 | LM337 | TO-220-3 – Adjustable negative voltage regulator | 1 |
| U5 | 7915 | TO-220-3 – Fixed -15V negative voltage regulator | 1 |
| U6 | 7815 | TO-220-3 -Fixed 15V positive voltage regulator | 1 |
| U7,U9 | 15*10.5*21 | Heatsink | 2 |
| U8 | NE5532P | DIP-8 – Dual op-amp | 1 |
BOM control potentiometer
| Parts | Value | Description | Quantity |
| CN1,CN6 | IN | 3P terminal | 2 |
| CN2,CN7 | OUT | 3P terminal | 2 |
| CN3,CN4,CN5 | 353120360 | 3P terminal | 3 |
| R1 | Potentiometer | RES-ADJ-TH_RK16312A0BKR | 1 |
| R2 | Single potentiometer | Potentiometer | 1 |
| R3,R4 | Dual potentiometer | RK097 | 2 |
Download files, links, and notes
Source: https://oshwhub.com/stupidso4/lm1875sheng-guang-gong-fang-ban
