Hi,
I have only just arrived here and may have the wrong story, here goes.
The safety earth MUST connect to all the metal chassis panels.
The safety earth does not have to connect to any of the grounds serving the amplifier. The amplifier can be electrically isolated from the chassis, there is no safety issue here. The transformer primary is isolated from all amplifier stages and the transformer core must be connected to chassis if any metal parts are exposed. A toroid has the core fully isolated from external contact and so does not need an earth connection. An electrostatic screen can be connected to earth.
Safety issues all attended to.
Consider now the amplifier operation; all the grounds need to be interconnected in a manner that permits proper operation of the zero volt references. There are at least three different schemes using direct links, resistors, capacitors and diodes and probably some others I am not aware of.
Any combination of these including disconnection from the safety earth are viable alternatives and none will compromise safety.
To recap mains powered equipment with a conductive chassis MUST have a safety earth; chassis to cable to plug top to power socket. All grounds can be tried in any combination until a successful version is found.
Good luck & don't take any chances that risk killing you.
I have only just arrived here and may have the wrong story, here goes.
The safety earth MUST connect to all the metal chassis panels.
The safety earth does not have to connect to any of the grounds serving the amplifier. The amplifier can be electrically isolated from the chassis, there is no safety issue here. The transformer primary is isolated from all amplifier stages and the transformer core must be connected to chassis if any metal parts are exposed. A toroid has the core fully isolated from external contact and so does not need an earth connection. An electrostatic screen can be connected to earth.
Safety issues all attended to.
Consider now the amplifier operation; all the grounds need to be interconnected in a manner that permits proper operation of the zero volt references. There are at least three different schemes using direct links, resistors, capacitors and diodes and probably some others I am not aware of.
Any combination of these including disconnection from the safety earth are viable alternatives and none will compromise safety.
To recap mains powered equipment with a conductive chassis MUST have a safety earth; chassis to cable to plug top to power socket. All grounds can be tried in any combination until a successful version is found.
Good luck & don't take any chances that risk killing you.
Dear All
If I'm wrong, please correct me.
I have two possible ways how to lift and connect it to the earth.
1. All inner grounds --> star ground (lifted) --> through bridge diode (or thermistor) --> chassis --> directly to the earth ground.
2. All inner grounds --> directly to the chassis star ground --> through diode (or thermistor) --> to the earth.
If I am right, we do not need to insist only one way. Two alternative solutions could provide a convenient choice.
Regards
jH
If I'm wrong, please correct me.
I have two possible ways how to lift and connect it to the earth.
1. All inner grounds --> star ground (lifted) --> through bridge diode (or thermistor) --> chassis --> directly to the earth ground.
2. All inner grounds --> directly to the chassis star ground --> through diode (or thermistor) --> to the earth.
If I am right, we do not need to insist only one way. Two alternative solutions could provide a convenient choice.
Regards
jH
Hi,
and what if the diodes (semiconductor) blow open circuit before the fuse (metal)? Semiconductors have a reputation for blowing long before the copper fuse melts.
Fault currents can run to many kA.
NO! you must connect metal chassis permanently to your mains safety earth.
You can still lift your ground from safety earth and/or isolate it from safety earth with that combination of resistor or diode or capacitor, as well as a direct connection to safety earth.
remember your input RCA, amplifier and PSU should all be isolated from the chassis and your only connections should be through your grounds.
You can have the safety earth AND your ground lift. Go and look at your layout again and review the advice you have already been given.
and what if the diodes (semiconductor) blow open circuit before the fuse (metal)? Semiconductors have a reputation for blowing long before the copper fuse melts.
Fault currents can run to many kA.
NO! you must connect metal chassis permanently to your mains safety earth.
You can still lift your ground from safety earth and/or isolate it from safety earth with that combination of resistor or diode or capacitor, as well as a direct connection to safety earth.
remember your input RCA, amplifier and PSU should all be isolated from the chassis and your only connections should be through your grounds.
You can have the safety earth AND your ground lift. Go and look at your layout again and review the advice you have already been given.
I like to develop a wood-clad aluminum plate of about 10mm thick (9mm wood and 1mm aluminum). Wood side forms outside of the box, giving a nice look and safety out of the electrical threat from the inner side. Meanwhile, aluminum side forms inside walls, giving a protection out of magnetic threat from the outside world. Sure, the heat sinks and the connecters should stay inside. ... mmm... need market investigation...
Regards
jH
Hi,
aluminium will not reduce or remove the magnetic radiation either coming in or going out. You need an iron alloy to do that.
A wood box would be nice but introducing a metal lining increases the electrical risks, however the metal also gives you a heat conductive surface and if properly constructed can reduce or eliminate electrostatic interference.
The wood box does increase the fire risk but if carefully thought out with accurate fusing most of these risks can be managed.
aluminium will not reduce or remove the magnetic radiation either coming in or going out. You need an iron alloy to do that.
A wood box would be nice but introducing a metal lining increases the electrical risks, however the metal also gives you a heat conductive surface and if properly constructed can reduce or eliminate electrostatic interference.
The wood box does increase the fire risk but if carefully thought out with accurate fusing most of these risks can be managed.
Hi,
I didn't say No!
just made you aware of some pros & cons.
Others have made non metallic enclosures even wooden ones.
I have seen valve gear inside wood cases & presumably hadn't caught fire before the photo was taken.
A claimed advantage of not using iron for the enclosure is freedom from interactions with currents in the electronics.
Go ahead & let us know of your results.
I didn't say No!
just made you aware of some pros & cons.
Others have made non metallic enclosures even wooden ones.
I have seen valve gear inside wood cases & presumably hadn't caught fire before the photo was taken.
A claimed advantage of not using iron for the enclosure is freedom from interactions with currents in the electronics.
Go ahead & let us know of your results.
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