Summary： This is 5.1 Channel Amplifier Board. On a single board, It has 7x IC's (TDA7294) out of which 5 are used as mono channels (90w each) and 2 are used in bridged configuration (170w), Also, this board has inbuilt power supply and Heavy Heatsink with a cooling fan mounted onto the PCB itself with it's separate regulated power supply. This board requires 24-0-24 VAC Transformer to work optimally.
INTRO :-
we have made a 5.1 Channel Amplifier Board using TDA7294 Audio Amplifier ICs. On a single board, there's a 5.1 channel amplifier circuit using 7x IC's (TDA7294) out of which 5 IC's are used as single ended (90w at 4ohm each) and 2 IC's are used in bridged configuration (170w at 8 ohm) for subwoofer channel. Each channel has it's own input and output. This board has very heavy heatsink that is recommended for cooling of these 7 IC's and also There's a FAN mounted onto the PCB with it's own regulated 12V power supply circuit. This board also has inbuilt Rectifier dual supply with 22000uF/63V capacitor on each rail and with fuse protection. The board requires 20-0-20VAC to 24-0-24 VAC Transformer to operate optimally.
**The IC used in this project is TDA7294 , Refer it's Datasheet for more details :- https://www.st.com/resource/en/datasheet/tda7294.pdf
Steps for the Build :-
1) First step is to get the PCB. Here' you can either Make PCB yourself by DIY method of Ironing. The PCB design is kept single layer only due to simplicity of making of PCB or you can get the readymade excellent quality PCBs from PCBway.
2) After PCB, carefully mount all the small components like jumpers, resistors, diodes etc. on the PCB and trim their terminals and solder them on the PCB first because there are many components in this Board so, it's better to solder them few by few
3) After mounting small components, mount big components on the PCB like Capacitors,fuse holders, rectifier and solder them. (Do not mount the Power Filtering Capacitors, 22000uF caps yet. that is to be done in later step.)
4) After that, now it's time to mount all the 7 IC's on the PCB and solder them.
5) Now Mount the heatsink properly on the IC's by using insulating MICA and insulating plastic shoulder washer. remember to use good thermal paste in between heatsink and ICs.
6) After mounting the IC's on the heatsink. Take a multimeter and check the Continuity between heatsink and IC's back plate. there should not be any continuity between them. All IC's should be insulated from Heatsink.
7) Now Mount the cooling fan onto the PCB using cable tie or any other suitable method.
The Board assembly is now completed. Clean the Track side of board with IPA (Isopropyl Alcohol) or cleaning flux and then power the board using 20-0-20 VAC transformer or 24-0-24 VAC transformer.
Remember while turning on the board for the first time, it is highly recommended to use a series bulb circuit to protect the board or any other damage in case if the board has some issues like short circuit, wrong component placement, any Faulty IC etc.
The series bulb would glow first then it turns off. Note here that, because this board has 7 IC's all are class AB amplifier IC's, each of them takes some current (approx 0.1A) at idle resulting in approx 0.7 to 0.8A current at idle for the entire board so as a result the series bulb would not completely turn off and rather stays on a little bit. you should definitely see the reduced brightness of the bulb that tells the board is running good.
Now check the input and output voltage of each of the channels. there should be approx. 0 voltage across inputs and outputs of every channel.
Now Finally, you can connect the speakers to the amplifier board, Give input signal to it and listen to the music and appreciate your hard work and Accomplishment.
