1.This board has voltage amplification independent power supply and voltage + amplification power supply, please tell us what kind you need, or we will ship you the second one ( voltage + amplification power supply).

2. --- If you need to switch between class A and class AB , please let us know, if there is no note for it,we will ship you the board which one can't switch between class A and class AB. class A and class AB no need to switch, it will affecting the stability of the circuit .

Materials:

1.The board with 2.0 mm double-sided design, 1% error of the metal film high precision, thick thick boulder foot resistance Taiwan, the load resistance Nissan KOA no sense of power resistance, capacitor using Japan ELAN and Panasonic fever capacitors, power Tube with a new original ON Semiconductor audio tube (MJL4202 and MJL4281 tube king) 3 pairs of 6 per channel. Excitation tube and voltage amplifier tubes were used (MJE15035 / 15034 and MJE15033 / 15032) audio on the board of the overall top materials, components arranged rectifier, circuit design is reasonable, pure and sweet sound quality, outstanding performance details. Sound warm and smooth. Dynamic and powerful, the general large food speakers can be plexus to promote

2. Integrated speaker protection circuit board, protection circuit is supplied separately, non-interfering.

Amplifier board basic parameters:
Amplifier board input voltage: positive and negative 30V-60V DC input.
Output power: A class 50W + 50W without distortion power, A class B is 350W +350 W without distortion power output.
Output impedance: 4-8 ohms
Speaker protection basic parameters
The original European OMRON silver contact relay, reliable contact
7812 power supply, more stable performance.
Supply voltage: AC 12-18V 0.2A 3W or so on.
Through circuit red light, the circuit is normal green light 3-5 seconds. Circuit start,
The maximum load power 400W, midpoint potential drift 1V, start protection

Recommended transformer parameters: Dual 28-38V dual AC output power (500W and above)

Power amplifier board debugging rules:

 Class-A amplifiers have long been the primary enthusiast's coveted amplifier because Class-A amplifiers have low crossover and even-order distortion, making the timbre the same as the amplifier while having the low-frequency dynamics and potential of a transistor, but since it works In the non-linear state, so the high precision components, assembly and commissioning difficulties, a little less attention is the fireworks, which makes a lot of entry-level enthusiasts discouraged, I recommend to you here a easy assembly, commissioning simple original American Kelly KRELL KSA50 amplifier circuit, the power output of up to 50W Class A output and Class A and B 300W output.

Median Potential Adjustment: (We have made a preliminary adjustment)

The multimeter dial DC voltage to 2V voltage file black pen on the output GND, red pen on the output OUT. Adjust the potentiometer RW35 finely until the multimeter reads below 5MV.

Quiescent current adjustment potentiometer for the RW36 clockwise to adjust the current, counterclockwise current down

1: Check the wiring is not connected wrong, the string on the positive multimeter, multimeter to ensure accurate readings. Adjust the trimmer potentiometer screws, cold current transfer to about 500 mA. Then the radiator slowly heat up, then the current will slowly increase, which is a temperature drift, to about 800 milliampere radiator temperature should be below 70 degrees, hands on it at least insist for 2 seconds. If it is too hot, reverse the current will be small. To ensure that the radiator current does not exceed 1 amp hot, the radiator temperature does not exceed 70 degrees, because the amateur case, the user usually only one multimeter, the positive current reaches 800 mA. This debugging radiator can not be less than 2.0 kg.

Recommended quiescent current: 1.2 A Radiator 4 kg or more

During debugging. Customers need to carefully observe the temperature and current, and can not leave. Note that the temperature difference between the thermal plate and the radiator, if the temperature difference is too large, indicating that the thermal plate is not in good contact with the radiator, you should check the cause.
 

Circuit board symbol symbols wiring instructions:

VC +  ----  positive pole of the power supply
VC -   ----  negative pole of the power supply
GND  ----  power ground
VA +  ----  Voltage Amplifier Independently powered positive positive
VA -   ----  Voltage Amplifier Independently powered positive

GND ground
INPUT signal input
OUT connect speaker

AC 12 AC speaker protection power Supply 12V AC

Package:

1 x  KRELL KSA50 Pure Class A HiFi Amp Power Amplifier Plastic-encapsulated Tube

12 x stainless steel screws & spring washers
1 x signal line(need to be cut)
6 x copper wiring card
（6mm heat shrink tubing not include,need prepared by yourself)

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