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Old 8th July 2010, 11:57 AM   #11
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Anybody?
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Old 8th July 2010, 01:01 PM   #12
AndrewT is offline AndrewT  Scotland
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post5 links to all the answers.
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Old 8th July 2010, 03:12 PM   #13
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Quote:
Originally Posted by pacoblackxx View Post
what about my last question?
The answer to that depends on whether those grounds on the pcb were already connected or not. Did you find out for sure?
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Old 8th July 2010, 09:27 PM   #14
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Yeap i checked today.The grounds of the pcb are independent..so?
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Old 9th July 2010, 10:24 AM   #15
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Default Single point grounding sequence

Well the way I'd do it (bearing in mind there are dissenting views here) is have a bolt (say M3) for the chassis connection which is mechanically fixed to the chassis. That takes care of your safety earth because the first tag to go over the bolt is the earth wire from the mains inlet. The next tag is the highest current one - to the power (main-gnd) ground - that's the centre point of your main rail caps. Over that tag goes the speaker ground (spk-out-gnd). Next up is the decoupling ground from your pcb, which I take to be pwr-gnd in your nomenclature. After this I'd have a tag which goes direct to the screen of your input cable - don't bring the screen connection onto the PCB as this ground is noisy with RF. The last ones on are the quietest signal grounds - i.e. pot-gnd and sig-in-gnd. These last two could even be combined together, no real need for separate connections. Then fit an M3 nut and tighten them all down nicely so they lead out in the form of a star.
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Old 9th July 2010, 02:36 PM   #16
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I have a bolt and nut holding the safety earth to the case (using an earthing lug in the power supply and a ring terminal in the amp case), and then ground wires with ring terminals and an additional nut. That way I can remove the ground wires and the safety earth is always still connected.
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Old 9th July 2010, 08:36 PM   #17
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posts 15 & 16 show the way.

I usually make a version of this.
Safety Earth beside the mains input cable, or IEC socket.
Chassis connection for Grounding the Audio side near the centroid of all the other grounds. This is rarely near the mains Safety Earth.
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Old 11th July 2010, 06:01 PM   #18
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Quote:
Originally Posted by abraxalito View Post
Well the way I'd do it (bearing in mind there are dissenting views here) is have a bolt (say M3) for the chassis connection which is mechanically fixed to the chassis. That takes care of your safety earth because the first tag to go over the bolt is the earth wire from the mains inlet. The next tag is the highest current one - to the power (main-gnd) ground - that's the centre point of your main rail caps. Over that tag goes the speaker ground (spk-out-gnd). Next up is the decoupling ground from your pcb, which I take to be pwr-gnd in your nomenclature. After this I'd have a tag which goes direct to the screen of your input cable - don't bring the screen connection onto the PCB as this ground is noisy with RF. The last ones on are the quietest signal grounds - i.e. pot-gnd and sig-in-gnd. These last two could even be combined together, no real need for separate connections. Then fit an M3 nut and tighten them all down nicely so they lead out in the form of a star.

I cant understand what you mean with the bold sentence. Which is the screen of input cable?

Correct me if i am wrong: the rca-ground goes to the pcb signal-in-ground. The pot ground goes also to the pcb signal-in-ground.then a wire must start from pcb signal-in-ground and then joined with the M3 bolt? Which is the screen of input cable?
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Old 11th July 2010, 08:39 PM   #19
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Quote:
Originally Posted by pacoblackxx View Post
I cant understand what you mean with the bold sentence. Which is the screen of input cable?
a coaxial cable has an inner and an outer.
The outer is the screen.
The inner is the core.

It is usual to send the signal through the core and bring back the return through the screen.
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Old 12th July 2010, 01:13 AM   #20
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Quote:
Originally Posted by pacoblackxx View Post
I cant understand what you mean with the bold sentence. Which is the screen of input cable?
I see Andrew has replied to clarify this point.

Quote:
Correct me if i am wrong: the rca-ground goes to the pcb signal-in-ground.
According to the way I do things, this is wrong. The rca-ground is the same as the screen of the input cable. Don't bring this onto the pcb if you want the best transparency of your amplifier. It carries RF because the cable to your CD player (or whatever source you're using) is an antenna. It also carries hash from the mains back to safety earth because many source components are not grounded nowadays, they tend to be double insulated. So for both of those reasons its sub-optimal to feed all that noise onto your amp pcb.

Quote:
The pot ground goes also to the pcb signal-in-ground.then a wire must start from pcb signal-in-ground and then joined with the M3 bolt?
Yes, you may do it this way - I offered that as an option in my earlier post. The pot ground may be combined with the pcb signal-in-ground and the two of them only need one wire back to the M3 bolt.
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