World famous machine

AUDIO NOTE KIT ONE (Duplicate Edition) 300B Electronic Tube Bile Machine

Let's discuss the circuit of 300B, the world's classic machine. I believe that everyone who used the original machine will praise it vertically, but most of the enthusiasts bought it from home. The results were disappointing. The circuit of this machine is extremely mature, but it is also an extremely designed circuit. If you don't have the connotation of read-through circuit, no matter how you imitate and put more expensive supplements, it will not have good results, because the manufacturer is designed by combining the winding method of output cattle with the circuit! This kit focuses on two points: the first level of 6SN7, because this tube is very linear, the British manufacturer also designed a limit parameter value, if your tube internal resistance is not low enough, according to the original circuit value, the working point must change, but also work in a good linear area, if this level is not good enough. If something goes wrong, all the efforts will be wasted. Therefore, it is suggested to use imported pipes produced in the early stage. The characteristics of pipes in those years are not much different from those of this circuit. There is also some objection to canceling the first stage cathode capacitors. The theoretical noise and gain change are not great, and the distortion will be reduced, but why can't we cancel them? Because after canceling, it becomes negative feedback of current mode, the output impedance exceeds 100K impedance of the original machine! Second point: load impedance of output transformer. It's not that the random load impedance of our usual circuit is not a big problem, but the power size and distortion change is not very big. But why should the circuit strictly require the working point? Because the original machine is designed at the circuit level of the limit of 80MA, you think that if the parameters are changed randomly, the voltage must rise, and all the work points in front of it have been changed. The cathode voltage of the front stage increases and the current decreases proportionally. We know that the lower the current, the thinner the texture of the sound. More terrible original machine several deletion limit current resistance also used very big...

Machine components:

Cabinet: 1.5MM thickness, more vivid voice, quieter background

Transformer: Power transformer 300W114*70 (Upgraded UK notched Red Bull Core), Choke coil 76*50 (UK notched Red Bull Core), Output transformer (UK amorphous 8C alloy core)

Electron tube: 300B (HI-FI of noble voice), 5687 (GE), 6H8C (6sn7) (Soviet Union). 5Z3j original box (dawn)

Resistance and capacitance accessories: 100K (alps27), coupling capacitor (large S, rifa), cathode capacitor (Philips), resistance (Taiwan), 300B tube seat (American CMC)

Power: 8W+8W

Three-dimensional: 400 * 300 * 60 (mm)

Weight: 16.8Kg

Function: High voltage protection with 20 seconds delay

Output impedance: 0-4-8

Craft: Hand-built shed

Welding Picture Reference：