Introduction to LClassA Hifi amp board
![](https://img.alicdn.com/imgextra/i4/13795664/T27WS7XXJbXXXXXXXX_!!13795664.jpg)
1. Purpose: The main purpose of the design is to add high-quality amp output to the decoder.
2. Working voltage: ±12V-±18V DC input.
3. Static working current: about 60mA.
4. Brief introduction of the circuit:
It adopts the mature circuit of op amp + middle power tube to expand the current, and increases the working current of the push tube to make it basically work in Class A. This method is adopted by many famous machines, such as Lehmann, Beyerdynamic A1 and other famous machines , Are basically optimized versions of this circuit. The driving ability and quality are not comparable to a simple op amp driver. This machine''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''s amp can perfectly drive high-impedance headphones such as HD650 and DT990.
- The voltage amplifier operational amplifier adopts the fever operational amplifier JRC5532DD.
- The driving power transistor uses BD139/BD140 for current amplification. This pair of tubes is adopted by the W yuan-level A1 amp, and its quality is self-evident.
- In principle, the function of the headphone amplifier is to increase the output voltage amplitude and increase the current output capacity; from the effect, the headphone amplifier is used to improve the thrust, dynamics, and sound field, improve the overall momentum, and make the sound fuller.
- Dual 15V power supply can provide more than 15V output voltage amplitude, which is a necessary condition for driving high-impedance headphones!
- Adding a current expansion transistor makes the output current capacity of the amp in the hundreds of milliamperes. Only in this way can it be possible to drive good headphones with low resistance and high current like K701 and 240S.
- The openings of this amp board are compatible with the most commonly used 1506 E3 chassis openings on the Internet.
5. The kit price is 29.8 yuan, including all the components and PCB in the picture, the finished board is 49.8 yuan, optional upgrades:
- The operational amplifier is upgraded to OPA2604 patch to in-line, +8 yuan; upgrade to OPA627au single to double, +18 yuan;
- Upgrade the decoupling capacitor to Panasonic FM330uf +2 yuan;
- Upgrade to ALPS 16 potentiometer +11 yuan;
- The cross-linked capacitor is upgraded to Panasonic BP-S non-polar capacitor, +1.2 yuan.