New KRELL KSA100 improved BA15MKII power amplifier DIY kit
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10KHZ Fang Bo
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50KHZ square wave, the board input low-pass is 1K resistance, 220P ground capacitance.
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8R+1U capacitor capacitor test, 10K wave, 5VP-P wave voltage, very good, very good stability.
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Oscilloscope 5MV file, the input 600R resistance landing noise level, less than 2MV.
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PCB board optimization to open a total of four boards were put up, without any BUG. This set of boards I have used more than five years of debugging, Taobao has a number of shops clones and cottage, the price is much lower than my, but a penny of goods, the other board of the tubes are not genuine, Not K170 / J74, the sound is far worse. Resistance is also made of knockoff.
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&x27;s amplifier circuit to the high-frequency sound and KRELL&x27;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.
3, the current amplification level: usually with a 150W / 8R of the end of the high-power machine will generally be used 3 Darlington, 3 Darlington current amplification capability, high and low frequency extension is good, but less than the tube, Poor stability will be poor. 2 Darlington relatively high and low frequency extension is not 3 good, but the circuit will stabilize a little, the density of the IF a little better. A pair of tubes less, reducing the difficulty of production. This circuit uses two Darlington, by increasing the drive-level current to make up for two levels of Darlington current amplification problem, and this circuit voltage amplifier circuit quiescent current 25MA, to further compensate for the two Darlington insufficient. So that two Darlington can drive three pairs of high-power tube, as long as the power enough, can output 150W / 8R, 300W / 4R. In this level of the drive tube (Q13Q14) 5171/1930 (15034/35) operating current is 60-80MA, three pairs of power tubes 5200/1943 (4281/4302) per tube current is 50-400MA. Another PCB board has two drive tube installation bit, can be installed MJE15032 / 15033, K214 / J77 and other tubes, a variety of games are played, do not twist pin.
4: mid-point zero and feedback circuit: zero point is not used active servo is a fear of complexity, the second fear of doing bad sound effects (this may be my psychological role) did not use the ordinary in the input stage Of the S-pole or the main voltage amplifier in a tube emitter plus a fine adjustment zero. But to learn the circuit KAS100 plus, R39, R40, R41, D1, D2, and other components of the mid-point zero, plus the benefits of these components are: DC balance without damaging the circuit AC balance .
As long as the installation is correct, the power is good enough, the board has a very good low-frequency driving force, thick warm and smooth IF, transparent high-frequency, if the sound has further improved (better low-frequency control and higher Sound density), it is recommended to push the tube and the output high power tube with the pair (must be paired) ON of the MJE15032 / 33, 34/35, pushing the MJL1032 / 3281, 4302/4281.
If the technical problems of the best call: 13097842335
Feedback circuit in the feedback capacitor in the circuit can be normal after the capacitor short-circuit, and no feedback capacitor. Also try the different feedback capacitor tone.
Kit (complete list of all components of the dual channel, see table below)
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category | number | element | Number | Valence | Model | category | number | element | Number | Valence | Model | Remarks |
resistance | R0 | 6R8 | 2 | 0.8 | DALE | Capacitance | C5 | 470U/10V | 2 | 10 | Epoxy resin | Short circuit |
R1 | 2K2 | 2 | 0.8 | DALE | C6 | 1U | 2 | 2 | Red WIMA |
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R2 | 36K | 2 | 0.8 | DALE | C7-C12 | 62U/75V | 12 | 24 | Monori capacitance |
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R3, R4, R5, R6 | 47R | 8 | 3.2 | DALE | C13 | 0.1U/100V | 2 | 2 | Red WIMA |
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R7 | 110R | 2 | 0.8 | DALE | C14 | 4U7/63V | 2 | 1 | Import common |
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R8, R9, R10, R11 | 1K47 | 8 | 3.2 | DALE | C15 | 220U/50U | 2 | 1 | BC PH capacitor |
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R12 | 46K4 | 2 | 0.8 | DALE | C16 | short circuit |
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| short circuit | short circuit |
R13, R14 | 14K7 | 4 | 1.6 | DALE | C17 | 4U7/63V | 2 | 1 | Import common |
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R15 | 46K4 | 2 | 0.8 | DALE | C18 | 47U/63V | 2 | 1 | Import common |
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R16, R17 | 150R (1/2W) | 4 | 2.4 | DALE | C19 | 100U/63V | 2 | 1 | BC PH capacitor |
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R18, R19 | 75R | 4 | 1.6 | DALE | Diode class | H1, H2 | E-562 | 4 | 16 | Constant current diode |
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R20 | 1K47 | 2 | 0.8 | DALE | D1, D2, D3 | 1N4148 | 6 | 0.6 | PHILIPS |
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R21, R22 | 36R | 4 | 1.6 | DALE | D4, D5 | 1N4007 |
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