one. Design Idea of 845 Single Termary Axuators. 6H8C using pre-frequency voltage amplifier tubes, achieve more popular today and cathode follower connection SRPP circuits, the advantage of simple structure, good linearity, strong overload, phase shift circuit small, high input impedance, low output impedance, and mating with 6π3C preamplifier stage and after the completion of the task of pushing (this line there are many articles explain, not repeat them here). 2. Power amplifier stage and the driver stage, with the potential for the full 6π3C high-fidelity sound tube 845, without using the single-ended class A output the negative feedback circuit. As shown in the drawings a circuit diagram of the machine. Second, the optional components and production 1. From the output transformer is customized Kai Li Guanghan electrical plant, wherein the model (kse75A) of the output transformer, input impedance of 5.5kΩ, output 0-4-8Ω, power 50W, STAGED The product is designed, Seiko production, with the cable between the insulating layer as paper, high voltage, frequency characteristics, by using the verification with extraordinary force timbre and good insulation properties. 2. Power supply: The operating characteristics of single-ended class A amplifier, and the power of the high technical requirements, etc., the author uses a filament, high-pressure, high-voltage rectifying three transformers, prevent share a power source circuit causes channel crosstalk signal. 300W of power boosting transformer using disassemble items on a military communication device, from around the filament transformer. Full bridge rectifier circuit gallstone combination, this approach can meet the high-voltage power supply delay, which can effectively prevent high-pressure shock tube, to improve the life of the tube, but also make the sound appear as solid stable and vibrant, rich flavor and bile with plenty of power. Respectively made in different places 0.1nF / 850V oil capacitors, FRAK0470μF / 400V electrolytic Germany, Sweden RIFA470μF / 400V and the electrolysis Japan Chemical 470μF / 450V electrolytic capacitors, and the choke coil-shaped filter circuit composed Ⅱ (Practice proven to do so, particularly good filtering effect, highlighting the feeling is very quiet background). Connecting leads and conductive properties better "silver-coated copper" multi-strand copper wire. Finally, according to the circuit diagram lap welding, will not be explained. 3. Amplifier parts: base metal deposit design drawings metal processing plant, a 2mm thick pressed steel production. All mounting machine base connector and volume potentiometer. Mounting the transformer and a capacitor, and the ground is provided. Selected coarse-core shielded cable (proven to do so, particularly small hum noise) as the filament connecting line, and close to the bottom plate traces shield grounding. First boot test each filament voltage is correct. Single core shielded wire and silver plated RCA jack when Carter, welding signal line, and close to the bottom edge of the trace. Reasonable choice arrangement resistors and capacitors. First vacuum transfer gate, the gate is negative 6π3C about -14V. The gate 845 is negative -90V. Finally, high-voltage circuit is connected. It is worth mentioning that: the use of very simple circuit diagram of a capacitive coupling, since the Cl, C2, C5, C6 plays pivot role, I use a relatively high capacitance and series RIFA420 Swedish "Vitamin" silver film capacitor in parallel, the filter capacitors C3, C4 using FRAKO 220μF / 385V power. Allow. The cathode employed US DALE resistors are precision non-inductive resistor fever axial pin (made selection of other military resistance "red gun"), using the Netherlands bypass capacitor "Philips" capacitor. It plays a crucial role in regulating the tone of the machine. Third, inspection and commissioning 1. Or dummy load connected speaker. 2. Start over again: negative gate 845 is -90V, the DC voltage across the cathode resistance at this time is about 4V, according to I = V / R to obtain I = 4v / 41Ω = O.1A, the anode voltage of + 740V. 6π3C negative gate is -14V, at both ends of the DC resistance of the cathode voltage is 8V, empathy I = 8W180Ω = 43mA, the anode voltage of about + 200V (try to meet each specific data point voltage circuit marked), so that 845,6P3P its quiescent operating point Q located in Class a, Hi-Fj to ensure amplification. 3. Test adjustment: GB-98 using vacuum millivoltmeter, no measuring signal input, voltage across the load is 0.7 mV, if not up to this standard, it should check the correct wiring and the filter circuit. Measure the output power: input music signal, potentiometers in the maximum state, GB-9 type using the tube voltage meter measured load (8 ohms) at both ends voltage of 12V, the rated output power according to P = I * V, to give P = ( V / R) * V = 12 * 12/8 = 18W. Using Marantz CD-14 type, B & WN803 speakers, Macross RSC-CD signal line, MIT T2 bi-wire speaker wire, and fever were listening together: preferred a "Tsai oldies" of the three, beginning piano giving a sound like iron shelf stable sense, strings and soundboard vibration sound is very clear in the course of the previous elimination, just as it is between two speakers have a piano being played, followed by Tsai was full of magnetism let the machine's delicate singing portrayed after being plain do have some charm. Then select "half-dream" in "in that distant place," just feel setting sun, a voice floating on dark red prairie, overcast, foggy heard invisible, an irreplaceable talk let us feel language is a pale ...... like that, soft and not lack of passion, open and structured. Fourth, the characteristics 1. The use of a higher grade RC element (especially interstage coupling capacitor), so that a qualitative change the timbre, elegant and gentle, romantic and elegant. Rhyme melodious. 2. Get rid of the negative feedback circuit, so that the details of the music and increase the amount of information, low-bounce and strong, relaxed and natural, sweet and rich. 3. Interchangeability of the tube, using pre-6H8C, 6N8P, 6N9P, push tube with 6Ⅱ3C, 6P3P, EL34,6P6P, KT88, using the power tube 845, gate 211 must be used to reduce the negative pressure of about -30 V, is different timbre . (Iv) cheap, cost-effective. It is suitable counterparts have made practical ability., Technology zone
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