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Build this 50W DIY Hi-Fi Audio Amplifier with Protection Circuitry

Build this 50W DIY Hi-Fi Audio Amplifier with Protection Circuitry


Have you ever built a super cool Hi-Fi Audio amplifier with simple components at your home? If not, in this article Vladislav Damyanov here guides you to do so. He is pretty sure you are gonna love this.

This article narrates about making your DIY high fidelity audio amplifier with output transistor protection circuitry and 2-way speaker protection circuitry. Let’s discuss some striking features which might convince you to try making this amplifier.



  1. Input Sensitivity – 0.25mVmax – most phones output such a level
  2. Input Impedance – 470ohm – solely depends on R1. You can increase R1 to whatever value you wish or exclude it altogether, but i recommend you keep it at that. Most audio cards of both laptops and phones will handle such an impedance with ease.
  3. Frequency Response – 1Hz – 45KHz at -3dB
  4. Output Power – 50Wrms or 70W musical power
  5. Power Consumption – 95W
  6. Efficiency – 53%
  7. Ripple Rejection – -68dB – a good value, which will attenuate power supply noise to a few hundred mV. Since the amp is in class B, there will be no substantial current draw at idle state, so the 10mF capacitors will provide exquisite filtering. When signal is applied, the hum will still be so low, that it will be inaudible.
  8. THD+N – 0.007@50W/1KHz – This is the value of the power amp. Due to the need of preamp, the value will be slightly higher. This value is often not topped even by the best class A amplifiers, so the amp will have virtually perfect signal recreation. This value is often indicative and may vary to some extend. Worst case scenario is 0.05%, which is still perfect for all intends of purposes. The key moment is to keep the voltage gain of the power amp low, 4 in this case.
  9. The output transistors of this audio amplifier are protected from excessive current draw, as one would occur if the output is shorted out while the amp is cranked up to the max. The maximum current draw is 6.3A. The protection is realized by Q13 and Q14 and all the surrounding components in their immediate vicinity.



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