I'm building my first chipamp from an audiosector m4780 kit and a 300va 22v+22v antek transformer. For my first build i decided to assemble one stereo unit. I'm now ready to put everything into a test chassis but I cant figure out a few things. I was hoping someone could clarify.
The first thing i cant figure out is what should be grounded and where? I see from the schematic that there are 3 grounds coming from the amplifier board, zero from the rectifier board and the ground from ac power. I've read through a number of builds but can't seem to find what I'm looking for. I can see three extra connections points on the amp board two near the cz/rz networks and one labeled chg. Are these the ground points for the amp board? Should i connect all four mentioned grounds to the chassis?
http://www.audiosector.com/lm4780%20amp.pdf
The antek transformer has two pairs of red and black primary wires. Can i tie the like colored pairs together or should i run one pair to power and cap of the others? Here's some info on the transformer.
http://www.antekinc.com/AN-3222.pdf
Since this is my first build i was wondering if a fuse on the ac power before the transformer is good enough security for a beginner?
If i can find out how to post some pics i will. Thanks.
The first thing i cant figure out is what should be grounded and where? I see from the schematic that there are 3 grounds coming from the amplifier board, zero from the rectifier board and the ground from ac power. I've read through a number of builds but can't seem to find what I'm looking for. I can see three extra connections points on the amp board two near the cz/rz networks and one labeled chg. Are these the ground points for the amp board? Should i connect all four mentioned grounds to the chassis?
http://www.audiosector.com/lm4780%20amp.pdf
The antek transformer has two pairs of red and black primary wires. Can i tie the like colored pairs together or should i run one pair to power and cap of the others? Here's some info on the transformer.
http://www.antekinc.com/AN-3222.pdf
Since this is my first build i was wondering if a fuse on the ac power before the transformer is good enough security for a beginner?
If i can find out how to post some pics i will. Thanks.
What a great article Nuuk, thanks for taking your time and putting that together. It helps to have things explained step by step when your just starting out.
Now that i know what needs to be grounded can someone help find the location where I should ground the power supply? From what I gathered from the article I need to take the 0v lines from the rectifier and attach them to earth ground. The only problem i see now is it looks like the lines i need to ground also need to go the the amp board. If you look at the schematic for the rectifier board and the schematic for the amp board you can see that the four lines coming from the rectifier board go into the amp board (PG+ V+ PG- V-). Maybe someone that's assembled a kit like this could share what they did for the power supply ground?
Amp
http://www.audiosector.com/lm4780%20amp.pdf
Rectifier
http://www.audiosector.com/lm4780%20psu.pdf
I've also decided to add fuses after the rectifier board for at least a short time until i know things are working correctly. Is there a formula to calculate the correct amperage fuse to use?
Thanks for the help.
Now that i know what needs to be grounded can someone help find the location where I should ground the power supply? From what I gathered from the article I need to take the 0v lines from the rectifier and attach them to earth ground. The only problem i see now is it looks like the lines i need to ground also need to go the the amp board. If you look at the schematic for the rectifier board and the schematic for the amp board you can see that the four lines coming from the rectifier board go into the amp board (PG+ V+ PG- V-). Maybe someone that's assembled a kit like this could share what they did for the power supply ground?
Amp
http://www.audiosector.com/lm4780%20amp.pdf
Rectifier
http://www.audiosector.com/lm4780%20psu.pdf
An externally hosted image should be here but it was not working when we last tested it.
I've also decided to add fuses after the rectifier board for at least a short time until i know things are working correctly. Is there a formula to calculate the correct amperage fuse to use?
Thanks for the help.
Hi,
the power supply has two sets of flow and return.
It doesn't have, nor need another return (ground).
The amplifier has a Power Ground and I think it has a Signal Ground.
The speaker has a ground that comes back as the black amplifier terminal.
Each of the input RCA has a return. These are the barrels of the RCA sockets.
All these returns (grounds) must be connected together at the central star ground (I call it the Audio Ground).
To make the amplifier safe to use, we must connect the Audio Ground to Safety Earth.
The Safety Earth MUST be a permanent connection from the third protective earth wire to chassis. This MUST be a continuous cable from the mains input terminal to the permanent fixture to the chassis. Preferably very short and close to the input socket/terminal.
the power supply has two sets of flow and return.
It doesn't have, nor need another return (ground).
The amplifier has a Power Ground and I think it has a Signal Ground.
The speaker has a ground that comes back as the black amplifier terminal.
Each of the input RCA has a return. These are the barrels of the RCA sockets.
All these returns (grounds) must be connected together at the central star ground (I call it the Audio Ground).
To make the amplifier safe to use, we must connect the Audio Ground to Safety Earth.
The Safety Earth MUST be a permanent connection from the third protective earth wire to chassis. This MUST be a continuous cable from the mains input terminal to the permanent fixture to the chassis. Preferably very short and close to the input socket/terminal.
It's not only waste of time but it's dangerous for your speakers; in case one rail fails, you may get substantial DC offset at the otput and damage the speakers. That's the main reason I'm always against using fuses after rectifiers. Properly chosen fuse on transformer primary should be sufficient for protection.
Check this thread: http://www.diyaudio.com/forums/showthread.php?postid=1508956#post1508956 Although it's about LM3875, most of the info will apply to LM4780 as well.
Check this thread: http://www.diyaudio.com/forums/showthread.php?postid=1508956#post1508956 Although it's about LM3875, most of the info will apply to LM4780 as well.
with the-ve rail negligible 8v or so..4780 will motorboat..it shuts off at arnd 1v on negative rail. With +ve rail near 1V it continues to work ..but the output too distorted . I have two separate boards for +Ve and -Ve rails ..one of them was failing ..while switching it to different rails for checking ...noticed this.
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