I'm putting together an lm3886 kit from chipamp.com.
I've done some looking both here and via google regarding appropriate means of grounding. In this case, I am using an aluminum chassis.
Now, I will obviously be making a ground connection to the chassis, via a bolt/nut, with grounding lug(s) (the ring style, I would assume spades aren't as secure).
Where I run into confusion is exactly how to implement this. I've seen people use a multiple-terminal ring, which I can't seem to source. I've also read that the connection to chassis should not be shared by any other wires for safety/regulations purposes, though I've seen it done on countless pics.
So I have four options here:
1) Ground wire from mains input terminal goes to a lug fastened to a bolt, to which lugs/wires to ground points on the amp boards also attach.
2) Ground wire from mains input terminal goes to a lug fastened to a bolt, which has one other lug/wire going to a second bolt, to which lugs/wires to ground points on the amp boards also attach.
3) Ground wire from mains input terminal goes to a lug attached to a bolt. Ground wires from amp boards attach to a second bolt, which shares continuity to the first bolt only via the chassis metal.
4) Ground wire from mains input terminal goes to a bus. Another connection on the bus goes to a bolt on the chassis. Two other connections go to the amp boards.
Thoughts?
I've done some looking both here and via google regarding appropriate means of grounding. In this case, I am using an aluminum chassis.
Now, I will obviously be making a ground connection to the chassis, via a bolt/nut, with grounding lug(s) (the ring style, I would assume spades aren't as secure).
Where I run into confusion is exactly how to implement this. I've seen people use a multiple-terminal ring, which I can't seem to source. I've also read that the connection to chassis should not be shared by any other wires for safety/regulations purposes, though I've seen it done on countless pics.
So I have four options here:
1) Ground wire from mains input terminal goes to a lug fastened to a bolt, to which lugs/wires to ground points on the amp boards also attach.
2) Ground wire from mains input terminal goes to a lug fastened to a bolt, which has one other lug/wire going to a second bolt, to which lugs/wires to ground points on the amp boards also attach.
3) Ground wire from mains input terminal goes to a lug attached to a bolt. Ground wires from amp boards attach to a second bolt, which shares continuity to the first bolt only via the chassis metal.
4) Ground wire from mains input terminal goes to a bus. Another connection on the bus goes to a bolt on the chassis. Two other connections go to the amp boards.
Thoughts?
option 3)
gives the Safety required of the Permanent connection of Protective Earth (PE) to Chassis.
This is not a ground. It is Protective Earth often referred to as a Safety Earth.
This is the connection that blows the mains fuse if there is a catastrophic failure in the Mains wiring.
Please don't confuse this with ground.
There is another Safety requirement.
All exposed conductive parts must be connected to the protected Chassis.
This generally requires a connection from Main Audio Ground (MAG) to Chassis.
This connection does not have the descriptor "permanent" nor is it described as "direct".
I have interpreted this as allowing some latitude in how the MAG to Chassis connection is implemented.
I use the "Disconnecting Network" (DN) to make this connection, in some of my builds.
The MAG to Chassis connection MUST be capable of passing Fault Current to PE. This Fault Current can approach many thousands of Amperes (kA).
I have described the compulsory parts and the optional parts of the DN many times. ESP added a page to his website. Unfortunately ESP's diagram shows option 4) for the PE connection. Technically ESP diagram is wrong. But it does get the main message over.
gives the Safety required of the Permanent connection of Protective Earth (PE) to Chassis.
This is not a ground. It is Protective Earth often referred to as a Safety Earth.
This is the connection that blows the mains fuse if there is a catastrophic failure in the Mains wiring.
Please don't confuse this with ground.
There is another Safety requirement.
All exposed conductive parts must be connected to the protected Chassis.
This generally requires a connection from Main Audio Ground (MAG) to Chassis.
This connection does not have the descriptor "permanent" nor is it described as "direct".
I have interpreted this as allowing some latitude in how the MAG to Chassis connection is implemented.
I use the "Disconnecting Network" (DN) to make this connection, in some of my builds.
The MAG to Chassis connection MUST be capable of passing Fault Current to PE. This Fault Current can approach many thousands of Amperes (kA).
I have described the compulsory parts and the optional parts of the DN many times. ESP added a page to his website. Unfortunately ESP's diagram shows option 4) for the PE connection. Technically ESP diagram is wrong. But it does get the main message over.
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