EL34 single-ended Class A tube amplifier board kit (tubes not included)

This kit does not contain tubes and output transformers. You need to contact customer service for the finished board to change the price.

The production difficulty is simpler than that of ordinary discrete power amplifiers. The reason is very simple. You only need to weld it yourself, without punching heat dissipation holes, free debugging, few components, and no effect. After listening, you will forget the power amplifier you have done before.

Noble EL34 genuine licensed goods, the details are excellent

Some customers have reported that the resistance is not large enough, so there is no need to worry about it at all. It has been precisely calculated. For example, the cathode resistance current of EL34 is 50MA, and the power consumption generated by 330 euros is only 0,85W. We are equipped with 3W imported resistors. The absolute capacitance is abundant.

There seem to be more than 600 yuan of EL34 on the market, using 30 yuan a cheapest EL34 with a lower-end tube than 12X7 for front-end amplification, the output cow is also made of ordinary materials, the United States DALE resistance, Philips high-voltage capacitors These materials don't need to think about it. The cost is estimated to be around 400 yuan

The single-ended Class A bile power amplifier is the best bile power amplifier circuit for the human voice. The sound is warm and charming, the overtone is rich, and the human voice is very poisonous. But now in the commercial societyMany businesses directly use ordinary resistor capacitors, low-end 6P3p, 6N2 6N3 and the like, coupled with a few cheap huge rectifier tanks and low-quality output transformersInstall a beautiful shell, you can sell a good price, the actual sound is similar to the power amplifier IC.

This circuit uses 12X7 (or higher-end ECC83) as voltage amplifier, and Noble EL34B as voltage amplifierSingle-ended Class A output, the rectification part does not use inefficient bile rectification, bile rectification, a number of rectifier tubes and dozens or even hundreds ofrectifier tubeThe sound color is very different. Philips' rectifier tube and field tube electronic filter are used here, so that the overall background is quiet and the extension is very good. This promotes the Seas gold series used by yourselfE0049 + E0011 SpeakerExcellent.

This kit does not include tubes and output transformers. The price is 82 yuan, using imported resistors and Nikon high-voltage capacitors. Cathode capacitors use warm-sounding chemicals, and the sound matching is very good. If you want to make the cost lower, EL35 can be used for 6P3P generation, ECC88 for 12X7 generation, but6P3PThe power is smaller, actually you want more power, you can use it instead.KT88Just adjust the cathode resistance.

Matching all-aluminum chassis (excluding cow cover)

Notes:
The tube is a Class A single-ended output, and the tube temperature and cathode resistance temperature are a bit high. This is a normal phenomenon, and there is no cold tube.

Many people do the front stage of the bile, but the back stage of the bile is relatively small. The main reason is that the previous kit was too inhumane, troublesome wiring, large size, poor layout, a large number of connections to increase loss and reduce signal-to-noise ratio. The wiring of this kit is very optimized. Under the shielding state of the input terminal, the AC sound is unpleasant to the ear. The whole machine is free of debugging, and the wiring is extremely small. It only needs to lead out the wire of the output transformer. It is actually better than the power amplifier, because the components are small, debugging is free, and the output isolation transformer is 10 times more reliable than the relay protection of the stone machine

PCB size: 170x99mm

Weight: about 279
Transformer voltage: 230VX1 (It can range from 200V to 250V, greater than or equal to 300MA.) 6.3VX1 (2A current)

The output power of this kit is Class A 10Wx2, don't underestimate 10W, generally Class A 5W has excellent hearing and sound pressure in a small room.

Our store has launched supporting chassis one after another.

Production attention:
1 The bile is a glass product, be careful to collide, the bile temperature of the bile machine is relatively high, generally do not touch it with your hands at will, the principle of this light bulb is the same

2. The power supply is relatively high. Do not directly contact the high voltage with your hands when measuring. Although the current is very small and there is no danger, direct contact is still a little painful.

Physical picture of finished board

DIY parts bag pictures

Grounding method of front stage and power amplifier DIY
A bit of grounding, I think, can be divided into three levels: one is a bit of grounding at this level, the other is a bit of grounding at the PCB level, and the third is a bit of grounding at the system level, that is, the whole machine. Theoretically, a little grounding is good, but in these three levels, the further down, the more practical problems there are (such as too many ground wires, etc.). I have seen a few examples of overseas production that mention grounding arrangements, unless the line is particularly simple, it is mostly series grounding (that is, step-by-step grounding is connected in series according to the schematic diagram), or a little grounding and series grounding (that is, this stage uses a star-shaped one-point grounding, and then series connection step by step).
In addition, as an analog low-frequency amplifier, it is rare to use a large area of ground nearby, so it is generally necessary to avoid the ground wire forming a loop (to avoid causing the current of the later stage to flow through the ground wire of the previous stage). Since the amplifier is mostly two-channel, their two channels have to share a chassis, resulting in a common point. If it is not handled well, it is easy to form a loop current. This requires attention.
Regarding the grounding point of the chassis, the RCA connection (mentioned by friends above), the nearest transformer connection, and the nearest power supply connection are all used. What I want to say is that if the grounding point is far away from the RCA input terminal, there may be AC sound - it is said that the induction potential of the RCA and the grounding point is different - which can be solved by connecting a 0.01U capacitor to the chassis at the cold end (ground end) of the RCA socket.