PCB board had been optimized and modified for four times, Currently it has not any BUG. This set of boards I have used more than five years of debugging, Out there there are some sellers selling copy/counterfeit product on the market, The price is much lower but any penny means something,They use fake/knockoff transistors, Not K170 / J74 at input stage, The sound is horrible&sucks.
1. the circuit board size is 270X70MM, 2MM thicker board double-sided gold 75UM (2AZ) thicker copper thin FR4 board, left and right channel mirror image symmetry. High-current power line is the top and bottom are traces, a total of 30MM line width, strict point grounding, wiring, taking full account of the negative feedback selection point and output line selection point, differential tube thermocouple, current and voltage levels can be powered , Can be independent of the former high low power. : Circuit with UPC1237 speaker protection circuit, plus a perfect switch delay, midpoint protection, overcurrent protection circuit. High signal to noise ratio, dual mono power supply can be independent, but also with the power supply, absolutely no AC sound. As long as your power transformer and filter capacitor of good quality, strict production, the sound will make you satisfied. According to the direction you like the sound and the different supply voltage / current level of the last class, can do 50W pure Class A or 150W Class B amplification. The supply voltage can be operated in the range of -35V to + -70V. It is recommended to use the former high to low power supply, the voltage level is higher than the current level 6-12V, voltage amplification level regulator.
2. BA-15KMII input diamond diamonds diamond differential circuit.JFET with K170 / J74 (available K246 / J103), on the tube BC546 / 556 (available MPSA42 / 92), whichever sound thick.Each tube current is 2- 2.2MA. The main voltage amplifier stage: KRELL improved Esoteric A-100 circuit: Darlington-connected emitter plus constant current source collector grounded push-pull amplifier circuit. (Plus a constant current source machine has a better low-frequency control and more delicate sound, play KRELL line friends can try again, adding constant current source voltage to improve 5-10V,) take its common set circuit Output resistance is low, can greatly improve the linearity of the voltage amplifier stage, the front tube can be a larger current, and further to the main amplifier tube junction capacitance charge and discharge, the machine without any compensation capacitor can work steadily, greatly improving the high-frequency (Q11Q12) is available in C5171 / A1930, MJE15032 / 33, A968 / C2238 and other TO-220 package of the tube can also be used MJE340 (Q9Q10) with C2705 / A1145 operating current is 5.6MA, / 350, A1358 / C3423 and other TO-126 package of the tube, (board has two kinds of packaging tube installation bit) operating current is 25MA. This level due to the high voltage, current, static power consumption of about 1.5W, must add a larger radiator. Constant current source with a pair of E562 constant current tube. Experiments: This circuit has both gold-based common-base circuit or the use of Harvard Carden&39;s amplifier circuit to the high-frequency sound and KRELL&39;s common set push circuit (Darlington connection), the low-frequency thick Characteristics without the gold throat circuit frequency is relatively thin low frequency relative control power difference and KRELL circuit high frequency relative lack of shortcomings. Insufficient is the front tube to join the constant current source voltage to increase 5-10V, the power circuit is more complex.