Core line: refer to the high-end model SF200 of the British Seddon amplifier, the original price is 40,000 US dollars;
The input uses 2 twin FETs, Philips NE5534.
Magnification: 24.4 times; the original machine adopts passive preamp mode, potentiometer 50K;
Output power: 100w/8 ohms & 200w/4 ohms;
Output large tube: Sanken tube king 2SC2922/A1216, the thrust is equivalent to 3 pairs of common tubes in parallel. 230v/17A/200W/60MHZ.
Finished product sales: All finished boards pass the midpoint test, noise test, maximum output waveform test, etc.
Noise level: 0.2mV; input uses twin field effect tube, the noise is extremely low;
Midpoint voltage: 1mV; DC servo line, which makes the high and low sounds more transparent;
Supply voltage: AC33v*2; transformer single side 150w or more; left and right channels are separately powered;
Printing plate size: 210*83mm; three-tube horizontal installation, 2mm thick plate, 70um thick copper;
Class A current: When the temperature of the transformer and radiator is allowed, try to increase the quiescent current as much as possible. Feel the charm of Class A power amplifier (warm, transparent, good control) This board debugging method: The left and right channels of this board have an adjustable multi-turn potentiometer for adjusting the quiescent current of the power tube (class A current). After the board is soldered, turn the adjustable potentiometer counterclockwise to the head (the quiescent current is 0) before energizing. After power-on audition, confirm that there is no problem with playback, slowly adjust the potentiometer clockwise and simultaneously detect 0.22 ohm resistor voltage (for example, static power is 200 mA at 44 mV, and E-pair output of power tube can be measured with mV file). Adjust the quiescent current to the desired value. Note: Because of the temperature feedback, as the temperature of the heat sink rises, the quiescent current will be pulled down a bit, requiring multiple tests and debugging.
The following picture shows the finished board:
Highly reliable American Bangshi adjustable potentiometer KOA0.18 resistor
Rubycon new 50v10000uF ruby electrolysis (original machine use)
Sanken Guan Wang C2922/A1216
718 high precision boutique resistor Omron relay