Description:
Before purchase please Note : 
1. This SIGMA22 (Sigma) kit is only suitable for players with a certain electronic foundation and soldering iron soldering ability. If you do not have the ability to use it, please do not buy it.
2. Due to different purchase batches, some components will be replaced without any notice under the guarantee of quality.
3. This kit does not include a chassis and power transformer and 2 main filter electrolytic capacitors.
4. SIGMA22 PCB board size 150*90MM, 1.6mm, 2 OZ, blue.
5. When R10 is 10K, the output voltage is 23~24V (also the default output voltage of this kit), and the other is equipped with a 50K 3296 adjustment.
6. The AC voltage supplied by the board should not exceed AC35V.
7. For other output voltages, there is a rule of thumb that, under load, a voltage drop of approximately 8V-9V should be maintained through the mosfet.
8. This kit does not include insulation sheets (not insulated) and heat sink for power supply adjustment tubes, but with screws.
 
Original Overview:
σ22 ("sigma 22") is a high-performance DIY dual-rail, tracking, linear regulated power supply (PSU). Originally designed as a companion PSU for the β22 amplifier, the low-noise, high-current, excellent line/load regulation, wide-bandwidth, and stability characteristics makes it also ideal for other DIY stereo headphone amplifiers, preamplifiers, power amplifiers and other applications requiring a dual-rail regulated PSU.
The circuit uses all discrete components (no integrated circuits) in a complementary topology, and features high-current MOSFETs as the output "pass" devices. Please see the Tech highlights section for a description of the circuit design.
σ22 is the result of a community service project for the audiophile hobbyist. The schematic diagram is open source.  It is designed to be relatively easy to build, but it is not recommended as a first-time project for the beginner.
Original circuit's official website: https://www.amb.org/audio/sigma22
This PCB size is 150*90MM, thickness is 1.6mm, copper thickness is 2 OZ (70UM), blue board, tin spraying process.
Compared with the original, some optimizations have been made, such as:
1. The output 0.4 ohm resistor is compatible with vertical (pitch 10mm) and horizontal (pitch 20mm) packages.
2. The four power adjustment tubes can be installed vertically, or horizontally and at the bottom of the chassis. The horizontal screw-on fixing on the board has a U-shaped slot, which is more convenient.
3. The main filter capacitor is compatible with diameter 30MM, foot distance 10MM and diameter 18MM, foot distance 7.5MM. 
4. R10 for output voltage adjustment, compatible with 1/4W resistor and 3296 fine-tuning. 
5. The component lead pads are treated with thermal pad, and the special processing of high current is required to ensure the performance and the good soldering.
6. After the purchase , the circuit diagram corresponding to the board can be provided.
7. The output voltage adjustment of the board is as follows:
Output Voltage R10 Value Zener Diode (D5)
±36V            4.99K           BZX55C12 (12V)
±30V            6.81K           BZX55C12 (12V)
±27V            7.87K           BZX55C12 (12V)
±24V            10K              BZX55C12 (12V)
±15V           39.2K            BZX55C12 (12V)
±12V      not installed       BZX55C12(12V)
±9V        not installed       BZX55C9V1 (9.1V)
±5V        not installed       BZX55C5V1 (5.1V) or LM336-5.0 (ADJ pin unused)
8. The relationship between the output DC voltage and the secondary AC voltage of the transformer is as follows:
Output voltage Transformer secondary
±36VDC              dual 35V or 70VCT
±30VDC              dual 30V or 60VCT
±27VDC              dual 25V or 50VCT
±24VDC              dual 25V or 50VCT
±18VDC              dual 20V or 40VCT
±15VDC              dual 18V or 36VCT
±12VDC              dual 15V or 30VCT
±10VDC              dual 15V or 30VCT
±9VDC                dual 12V or 30VCT
±5VDC                dual 9V or 18VCT
 
Precautions:
1. Installation welding debugging This board needs to have a certain electronic circuit foundation, otherwise please do not shoot.
2. The current output capability of the power board is determined by the parameters of the four rectifier diodes and the power supply adjustment tube. When powering the high power amplifier circuit, be sure to dissipate heat from the rectifier and the regulation tube.
3. The BC546 and BC556 transistors on the board can be replaced by 2N5551 and 2N5401, but please pay attention to the CE pin.
4. For other output voltages, there is a rule of thumb that, under load, a voltage drop of approximately 8V-9V should be maintained through the mosfet.

Note:
Please allow minor errors due to manual measurement.
Item color displayed in photos may be showing slightly different since monitors are not calibrated same.

Package Contents: 1pc of Power supply Kit（not include the 2 main filter electrolytic capacitors）

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