SY,
I've been trying to remember what it was you said you were listening to. Cables perhaps? I seem to recall something about different metals, presumably the composition of the conductors. I didn't find the things you were listening to all that interesting, just your reaction to them. I doubt that there was anything easily searchable in your post (particularly given the limitations of the search engine here at DIY), after all searching for "silver" or "gold" or "copper" will give something close to a zillion hits for any member who's been here for more than six months. It'd be interesting to find the post--I'll keep prodding my memory to see if I can come up with something searchable. It's been at least two or three years, possibly longer. Given that the search engine has the ability to set time limits, that might help.
'Not allowed to' in this context meaning something that would leave one open to condemnation by one's peers.
Grey
I've been trying to remember what it was you said you were listening to. Cables perhaps? I seem to recall something about different metals, presumably the composition of the conductors. I didn't find the things you were listening to all that interesting, just your reaction to them. I doubt that there was anything easily searchable in your post (particularly given the limitations of the search engine here at DIY), after all searching for "silver" or "gold" or "copper" will give something close to a zillion hits for any member who's been here for more than six months. It'd be interesting to find the post--I'll keep prodding my memory to see if I can come up with something searchable. It's been at least two or three years, possibly longer. Given that the search engine has the ability to set time limits, that might help.
'Not allowed to' in this context meaning something that would leave one open to condemnation by one's peers.
Grey
Ask yourself...that sort of self-censorship is usually self-inflicted.
I tried "gold" as a search term and limited the search to your posts over a year old. Not as many hits as I feared, but none of them were the one I'm looking for. I've nearly convinced myself that you mentioned that you were listening to cables and I got the impression that you weren't on your system; somewhere else. Are you a member of an audio club out there? Possibly a demo in an audio shop? Over at John's? Something of that nature.
If I get time I'll take another whack at it with other search terms, but I'm at work and fiddling between the cracks and the search engine here drives me absolutely nuts.
Grey
I tried "gold" as a search term and limited the search to your posts over a year old. Not as many hits as I feared, but none of them were the one I'm looking for. I've nearly convinced myself that you mentioned that you were listening to cables and I got the impression that you weren't on your system; somewhere else. Are you a member of an audio club out there? Possibly a demo in an audio shop? Over at John's? Something of that nature.
If I get time I'll take another whack at it with other search terms, but I'm at work and fiddling between the cracks and the search engine here drives me absolutely nuts.
Grey
Rick Miller said:
One thing that is absolutely not negotiable is to ground the chassis to the mains earth (E?). That's a safety must-do. We should always take that for granted.
Then on the other hand we have the power- and signal circuits, interconnected at some point, and that has/is being discussed.
Then, do you have to connect those signal and ground points to chassis? I think you do, for the simple reason that leakage through the mains transformer and/or capacitors (people put capacitors between the weirdest points hoping it'll improve the sound) can float your entire circuit to quite high voltage. When it wacks you it'll probably not kill you, but lots of arms have been broken by people slamming them into walls or desks, jerking them away from a shock that in itself was harmless.
So my MO is a resistor to chassis to prevent the floating up, paralleled by a capacitor to ground against RFI. Something between 1nF and 10nF // 100 ohms seems to do the trick in most cases.
Jan Didden
But this solution for the Disconnecting Network does not survive the situation of a short from Mains Live to amplifier. In this case the Fault Current that flows to Safety Earth can be kA before the mains fuse ruptures and the arc extinguishes.janneman said:
Pass recommends a big Thermistor as part of the Disconnecting Network.
I have tested a 35A bridge rectifier as the Fault Current route to Safety Earth.
Do not rely on a resistor//capacitor. They cannot pass sufficient Fault current. They will burn out and may rupture before the mains fuse thus leaving the amplifier "LIVE"
I owe the result with 'proper' grounding scheme. Please compare with
http://www.diyaudio.com/forums/showthread.php?postid=1742422#post1742422
Jan, is there any problem with class II instrument?
http://www.diyaudio.com/forums/showthread.php?postid=1742422#post1742422
Jan, is there any problem with class II instrument?
Attachments
AndrewT said:
Good point! I normally worry about the signal integrity, and rely on the various fuses in the system for safety.
When you say that it takes some time for the fuses to cut (and the actual current is not relevant here for safety), what time frame are you talking about? Fractions of a second, I assume?
Jan Didden
AndrewT said:
OK, then my question is, must we go to heroic lengths to take care of that few mSec just before the fuse melts? I'm not saying we don't, but I don't see what we would gain.
Legal bodies here in Europe (and they are not known for being easy) seem to be content with the fuse as such.
Jan Didden
janneman said:
I think you got hold of the wrong end of the stick
The issue is not the time it takes to blow the fuse, but the passage to ground which is to carry the current to blow the fuse in the first place.
A cap and a resistor in parallel to safety ground, is most likely able to carry enough current to blow a small fuse as found in a pre amp, but in a power amp, that turns into a whole new game, as the fuses are big enough to blow a resistor.
That's where a bridge or a hefty thermistor comes in handy, as they both will offer some isolation under normal operation (0.7V or high resistance, respectively).
In a fault situation, they will both conduct enough current to safety ground, to blow even a 5A fuse.
Magura
The problem is that the Disconnecting Network (or a direct wire link) MUST SURVIVE longer than it takes the fuse to rupture and for the arc to extinguish.
Be mindfull that a higher rated fuse will take longer to rupture, (that's me back on my hobby horse promoting close rated fusing).
If the Disconnecting Network ruptures first because Live has contacted some part of the amplifier, then the Mains continues to keep the amplifier "LIVE" and the Safety Earth connection is now non existant.
The amp appears to be unpowered, due to the internal fault.
The listener goes across to wiggle some interconnects and someone else phones for an ambulance.
Be mindfull that a higher rated fuse will take longer to rupture, (that's me back on my hobby horse promoting close rated fusing).
If the Disconnecting Network ruptures first because Live has contacted some part of the amplifier, then the Mains continues to keep the amplifier "LIVE" and the Safety Earth connection is now non existant.
The amp appears to be unpowered, due to the internal fault.
The listener goes across to wiggle some interconnects and someone else phones for an ambulance.
Hi,
I am sorry that the following discussion is in french :
http://forums.futura-sciences.com/depannage/1585-pc-ampli-hifi-probleme-de-masse-2.html
For human safety and signal integrity, the advice of Bigonoff, who worked in medical services where both are subject of more care than anywhere else, is to adopt a general philosophy of equipotentiality and not to blindly adher to the vague rules "avoid ground loops" and "star point" without carefully looking at the current paths.
Found this for human safety :
http://www.ewh.ieee.org/soc/emcs/pstc/TechSpk/ground97.pdf
I am sorry that the following discussion is in french :
http://forums.futura-sciences.com/depannage/1585-pc-ampli-hifi-probleme-de-masse-2.html
For human safety and signal integrity, the advice of Bigonoff, who worked in medical services where both are subject of more care than anywhere else, is to adopt a general philosophy of equipotentiality and not to blindly adher to the vague rules "avoid ground loops" and "star point" without carefully looking at the current paths.
Found this for human safety :
http://www.ewh.ieee.org/soc/emcs/pstc/TechSpk/ground97.pdf
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