1. The noise of the switch is small and will not have too much impact on the speaker. It is recommended to add a horn protection circuit. The horn protection circuit can not only eliminate the impact noise of the power amplifier switch machine, but also avoid the output DC burning the horn when the power amplifier is . 2. The bottom noise is small. Zero floating small, do not need to do any debugging after installation, the output zero drift voltage will generally not exceed 50mv, and is relatively stable. 3. Free debugging. As long as the connection is correct, no one is wrong, basically it is a success, no need to do any debugging, beginners also have a very high success rate. Note: 1.2SC5200 + ZSA1943 are disassemble parts,but in good condition. 2.The PCB board has change to black, but the function is same. Operating voltage: Dual DC 10 - 45V recommended Dual DC 35V Rated output power: 100W(4 Ohm ± 35V) Maximum output power: 150W (4 Ohm ± 45V) enormous heat, is not recommended PCB size: 30 x 50 x 35mm Pitch: 5.08mm Hole distance between two power tube: 47mm color: As shown Material: PCB The panel color is random, no specification is accepted Package Contents: 4 x Amplifier board Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.