| Khron |
| I'm just curious... What exactly is the purpose of a 1 ohm resistor between the input ground and the "ground star" (as seen, for example, in the MyRef gainclones) ??? |
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| Upupa Epops |
| Supression of ground loops.... |
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| rcavictim |
!). Would act as a protection fuse to save the PC board from massive destruction in the case of the ground of the attached component becoming hot to the mains.
2). Would help reduce magnetically induced hum in the unbalanced signal conductor along the length of the shield in the interconnecting coaxial cable resulting from any AC mains current flowing as a result of voltage differential in the earth of the chassis of various system components.
3). In extreme cases will inspire a user who is not as brain dead as most, to think about it's purpose and perhaps even ask others "Why?" ;) |
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| Spasticteapot |
| quote: | Originally posted by rcavictim
!). Would act as a protection fuse to save the PC board from massive destruction in the case of the ground of the attached component becoming hot to the mains.
2). Would help reduce magnetically induced hum in the unbalanced signal conductor along the length of the shield in the interconnecting coaxial cable resulting from any AC mains current flowing as a result of voltage differential in the earth of the chassis of various system components.
3). In extreme cases will inspire a user who is not as brain dead as most, to think about it's purpose and perhaps even ask others "Why?" ;) |
I feel rather stupid asking this, but what exactly is a star ground? I'm familiar with the signal ground and power ground, but not the star ground.
Also, if I'm not mistaken, the speaker ground is connected to power ground, yes?
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| poobah |
It might make more sense the call it asterisk ground rather than star ground. It is the practice of bringing ALL ground connections to a single physical point.like a lug or a terminal. All ground connections "lead out" in a star configuration to the individual circuits.
It is done to prevent the small resistances and inductances in the ground connections from cross coupling (talking to each other). To see the problem more clearly; take a schematic and replace every ground connection with a small resistor... see what a mess things became??
It's not so hard to do but often misunderstood... post a schematic and people can tell you how to do the "star"
;) |
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| Stephen Morgan |
| quote: | Originally posted by poobah
It might make more sense the call it asterisk ground rather than star ground. |
Hmmm... and what is the root of the word asterisk? Hint: it's also in astronomy and disaster. ;) |
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| rcavictim |
| quote: | Originally posted by Stephen Morgan
Hmmm... and what is the root of the word asterisk? Hint: it's also in astronomy and disaster. ;) |
Besides J.P. Morgan didn't Tesla get some funding from a dude named "aster" representing considerable "risk"? Spelling stretch notwithstanding to promote joke value. :D
The connection to a good ground was well appreciated by Tesla BTW. |
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| Upupa Epops |
| Another example of star grounding.... |
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| Upupa Epops |
| And detail... |
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| Upupa Epops |
| And schematic ( for completeness... ). |
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| poobah |
Stephen,
I was thinking more in terms of Kurt Vonnegut's usage of the asterisk... think it was in "Breakfast of Champions".
* |
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| AndrewT |
Hi Upupa,
re posts 9 & 10: are the upper & lower star grounds connected by the bolt (set screw) through the rectifier sink?
That is probably the most (18) I have seen, ever! |
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| AndrewT |
Hi Upuppa,
is the 134/634 buffer based on the Jung topology?
Which chip is SMD? |
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| Upupa Epops |
| Hi Andrew, " main point " of grounding is below rectifier, both sides connected together... And WJ : yes, 634 have " diamond " topology. PCB is universal, for soic and dil opamps... |
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| dfdye |
| Dumb question, but why not use a ground plane instead of a star ground? |
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| poobah |
dfdye,
I use grounds planes all the time and then star them together at single point. Ground planes are not always good things. They can be handy shields, and they can control impedance for high speed stuff, but they can also be awesome couplers (un-wanted) as well.
So in the spirit of jneutronesque analosity, they should be applied thoughtfully... ground is a myth.
;) |
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| pinkmouse |
| Personally, I like separate ground tracks to a star, then flood everything else with the ground plane. I'm sure there may well be reasons why you shouldn't do it that way, but it's always worked for me. |
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| poobah |
That's an EXCELLENT way of doing it pinkmouse...
Flooding your boards with copper helps to keep them from warping in wave or reflow operations too. It's going to be worse with this new RoHS ****! |
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| pinkmouse |
| Pavel taught me to do something right then! Now we just have to work on the rest...;) |
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| dfdye |
| quote: | Originally posted by pinkmouse
Personally, I like separate ground tracks to a star, then flood everything else with the ground plane. I'm sure there may well be reasons why you shouldn't do it that way, but it's always worked for me. |
Nice suggestion. I will have to put that nugget in my little bag of tricks. |
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| mrlots2do |
| quote: | Originally posted by pinkmouse
Personally, I like separate ground tracks to a star, then flood everything else with the ground plane. |
What does this mean? |
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