HIFI KHD-2000 Fully Discrete Headphone /Table Amplifier PCB (HA5000 Type)


PCB size: 160X75X2mm
White letters on green background, 2OZ copper sheet tinning process, with component values on the board
 
Brief introduction of DIYER project:
Divide the HIFI-PCB system into three modules (power module, AMP module, protection circuit module) and several small modules (potentiometer module, signal selection module, single-ended to balance module, etc.); when fans are switching to other circuits , Only need to replace the AMP module, even the openings of the chassis and the heat sink may not need to be changed; it is convenient for the fans to operate and greatly reduces the repeated investment cost in the fever process; the ZERO-ZONE team is committed to HIFI-DIY promotes the development of a style similar to PC-DIY, simple and simple upgrade with low cost.
KHD-2000 project introduction:
The KHD-2000 series refers to the old iron HA5000 circuit, which optimizes and improves the following points:
1. The input stage single FET constant current source is improved to a dual-loop BJT constant current source with lower distortion, and the constant current number is set to be the same as the original machine, reducing unnecessary debugging;
2. Because the end tube uses MOS tube, and the MOS tube itself has a temperature coefficient (temperature compensation), we have changed the style of the original single BJT tube (N tube) as VBE, and directly use BJT pair tube (NP) as VBE Pressure control regulation.
3. The push tube adopts parallel tube, and the power output tube adopts unit parallel to enhance its dynamics, driving force and details.
4. The original machine uses a pure direct-coupled method, coupled with the power output of the MOS tube, which will reverse the conduction cooler and the warmer, and in winter and summer, the midpoint voltage changes greatly (a large deviation of 0MV), which will damage the headset ; To this end, we added a feedback capacitor and stabilized the midpoint voltage. The difference between the cooling and heating engine is less than 2MV, which is safe; this feedback capacitor is also one of the sound calibration methods. Different brands of capacitors will have correspondingly different sounds and extremes. Great to facilitate the school sound needs of enthusiasts.
5. The original machine adopts ordinary electronic filtering + voltage stabilization mode for the voltage amplifier stage and input stage. In order to achieve a better sense of hearing, we have changed to parallel class A power supply for power supply, which has lower ripple coefficient and better sense of hearing. good.
6. Modular structure reduces the investment cost in the later stage.
One machine with dual purpose (headphone amplifier/desktop power amplifier), plus or minus 24V power supply, voltage amplification stage, input level plus or minus 18V class A power supply, enough slewing to drive 4-600 ohm load; with our earphones-amplifier protection The circuit can be switched to an amp/desktop power amplifier, and one input can be equal to two systems.
It can effectively promote the HIFIMAN HE500 series earphones when forming a fully balanced version


Package:
1pc HIFI Enjoy KHD-2000 Fully Discrete Headphone Amplifier/Table Amplifier PCB (HA5000 Type)


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