Introduction:
The product uses 6J1 electron tube as the front stage to promote LM1875T power amplifier, with line output function. After being buffered by the 6J1 tube, the ‘digital taste’ and ‘transistor sound’ can be greatly reduced, so that the entire audio system has a sweet and natural ‘gut taste’, and the sound is sweeter and softer. It sounds better than the general LM3886 and TDA7293.
The front stage is the 6J1 fever tube front stage: the circuit principle design of the imitated music fax X-10D of the famous machine, with reasonable optimization, is more stable than the original machine, and the performance of the tube is increased by 10%. This machine uses dual AC12V input, so you don’t have to worry about finding a high-voltage power supply. The board comes with a booster that allows you to enjoy the flavor of high-voltage tubes under low power supply.
Working principle of power supply:
Turn on the power and the tube filament begins to heat up. At this time, the boost starts from zero voltage. When the tube filament is hot, the boost is just completed, so this is the same as the tube rectifier. The four 470UF capacitors are very clean and excellent. The power supply system will not have AC noise, the filament is DC 12V power supply, and the filaments that need two tubes are connected in series. The use of DC filament is also to reduce noise.
Automatically switch the line output after the front stage output or push the rear stage LM1875T power amplifier, that is, after inserting the line output hole, the power amplifier has no output. When the line output is not inserted, the power amplifier output is pushed.
Wiring:
Some friends hope that this product can directly drive earphones, and the 6J1 tube front output signal can also drive earphones, but the output sound is much smaller than the digital sound source, and the thrust is average. If friends can accept this method, then you can give it a try. With this product’s sound source processing, the earphone sound will also have a sweet and delicate ‘guts’. The line output function can also be used as the front-end output function, connected to other back-end power amplifiers.
Rear lm1875t power amplifier: adopt LM1875T classic design! The wiring is reasonable! Outstanding performance! Highly sought after by DIY enthusiasts! Retaining all the original wiring and maintaining the original performance, the original components have also been strengthened. After the introduction of the 6J1 tube, the sound is more sweet and beautiful!
Performance parameters:
Power supply voltage: The default dual AC 12v/current 3A, the power is above 60w, and the highest voltage cannot exceed the dual AC 18V, otherwise the tube will not light up and the sound will be distorted. If you need to use AC 18V and 15V to 43ohm, you need to modify the filament voltage drop resistance to 47ohm, and the output power of the power amplifier will be slightly higher at this time.
Front-end line output: the magnification is about 0.7 times (the amp function can be tried to use, it can drive high-sensitivity headphones, the thrust is average, the line output can be used for the current level function, the output is connected to promote other power amplifiers, and it has the taste of tube.)
LM1875t power amplifier output power: typical 20W (maximum 30W)
Speaker impedance: 4Ω-8Ω
Total harmonic distortion: <0.04%
Signal to noise ratio: 105dB
Frequency response: 14Hz-100kHz (the maximum range calculated by the RC high-low-pass circuit is 3.29Hz-482.29kHz)
PCB size: 100*87mm
Package includes:
1 x Front Board
Availability: 
Shipping: Free Airmail 
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