it was very very loud ... scaring i see. i wonder if taking the mains transformer out of the case could make things easier ? in that way the audio ground would be disconnected from the PE and not ground loop issues ? could i earth the transformer only ? after the transformer the voltages are much lower I am using low output voltage transformers like +/-30V max
I like a lot the idea of segregating the transformer in a separate casing like some manufacturers do.
And then connecting the mains transformer to the amp casing with a good section umbilical cord. I love it. Any magnetic field and vibration would be isolated from the amp circuits.
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It will create more issues than it solves I am afraid. You have special transformers that transform DC! 😀
Elektor magazine always had a safety page with all the local regulations and construction tips on mains cabling, fusing etc. Maybe you can find such an old magazine to gather knowledge. Doing things right is often relatively easy.
This is the dutch version, it helped me find my way long ago. Make sure to find a more recent Italian version with updated info on local regulations. The point is that describing matters in an easy way on 1 page for DIYers is not easy at all. I have not seen any other than the one by Elektor which goes to show some matters to be a little neglected despite the importance.
http://www.miedema.dyndns.org/fmpics/Circuits_online/Veiligheid-Pages_from_Elektuur_1989-12.pdf
Elektor magazine always had a safety page with all the local regulations and construction tips on mains cabling, fusing etc. Maybe you can find such an old magazine to gather knowledge. Doing things right is often relatively easy.
This is the dutch version, it helped me find my way long ago. Make sure to find a more recent Italian version with updated info on local regulations. The point is that describing matters in an easy way on 1 page for DIYers is not easy at all. I have not seen any other than the one by Elektor which goes to show some matters to be a little neglected despite the importance.
http://www.miedema.dyndns.org/fmpics/Circuits_online/Veiligheid-Pages_from_Elektuur_1989-12.pdf
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Can I politely suggest that the idea of changing the class of a device is let go.
A Class I device is designed to be a Class I device, and a Class II device is designed to be a Class II device. Provided they meet electrical standards one is not better than the other. And as soon as you try to convert them, technically you have made them unsafe. There is nothing to be gained from this, and rather than making the device safer you risk making it dangerous. It certainly won't meet safety standards, and may invalidate insurance if it causes a fire or other accident.
By all means replace a poor quality connector with a better quality version of the same connector. That won't change the design or safety of the device (providing it is done correctly).
That is in an ideal world. What one can see is that some devices slip through and have leakage on the chassis. I see such devices now and then, made by former reputable brands. In some areas certification can be done by the same company that produces the stuff...
If connecting a metal casing of an audio amplifier to PE causes fire I am curious how that can happen. Of course one must know stuff and not poke around when the knowledge is not there.
If connecting a metal casing of an audio amplifier to PE causes fire I am curious how that can happen. Of course one must know stuff and not poke around when the knowledge is not there.
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There is an alternative to mains connectors: a fixed mains cable, "grown" into the appliance.
Theoretically, you can convert a Class II appliance having metallic case to Class I. But then you have to connect all external metal parts (top, bottom, front, back, sides, if they are made of separate pieces of metal) to the PE with separate wires, and you have to use dedicated screws. Construction screws holding the pieces together are not allowed to use for conducting PE.
For example my CD player has a mold internal plastic structure, holding the mechanism, PCBs, etc. It is covered by a nice machined aluminium top and front, a steel bottom and wooden sides. If I wanted to convert it, I should provide a spade terminal screwed to the top and to the bottom, and attach PE cables to them. And then connect signal GND to PE, but prevent ground loop at the same time.
Theoretically, you can convert a Class II appliance having metallic case to Class I. But then you have to connect all external metal parts (top, bottom, front, back, sides, if they are made of separate pieces of metal) to the PE with separate wires, and you have to use dedicated screws. Construction screws holding the pieces together are not allowed to use for conducting PE.
For example my CD player has a mold internal plastic structure, holding the mechanism, PCBs, etc. It is covered by a nice machined aluminium top and front, a steel bottom and wooden sides. If I wanted to convert it, I should provide a spade terminal screwed to the top and to the bottom, and attach PE cables to them. And then connect signal GND to PE, but prevent ground loop at the same time.
If that would be 100% true then I have some crappy devices here on my bench 🙂 Let's suppose a cheap supposedly class II device in a metal casing will be fitted with a 3 pin IEC connector and then PE connected to chassis. What will the outcome of both the original situation and the modified situation be when there is a loose L wire touching chassis?
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I would like to thank you very much indeed for making me conscious of the big risk. From now on I will avoid any class II unit (not earthed).
I have seen that many high quality units are fully earthed ... so it is possible to make Class I and great sounding equipment that is also very safe for the users.
Of course if i will remove the lid to peep inside i will remove also the power cord.
No more Class II devices Thanks again gino
I have seen that many high quality units are fully earthed ... so it is possible to make Class I and great sounding equipment that is also very safe for the users.
Of course if i will remove the lid to peep inside i will remove also the power cord.
No more Class II devices Thanks again gino
Hm, there should not be any difference. Class II has double isolation internally between line and chassis. Line can't touch the chassis at a failure condition. There is no code that prohibits earthing the chassis. But sometimes it has some advantage, because there can be capacitive coupling between line and chassis, and the chassis could be at some AC potential that you can "feel" when you touch the case. Furtermore, in IEC Class II there is no filtering at the line/neutral/PE input.
As for audio, that is a special case regarding a potential ground loop.
Sorry i swear the last one.
Is there a way to earth the metallic enclosure of a class II amp and avoid any ground loop issue ? would just a 100 ohm resistance between the earth pin on the socket and the metallic cover be enough ?
Is there a way to earth the metallic enclosure of a class II amp and avoid any ground loop issue ? would just a 100 ohm resistance between the earth pin on the socket and the metallic cover be enough ?
When you ask that I think you need to have some assistance of an experienced person. This material can be tough to grasp when not experienced enough.
I say this because you propose an outright dangerous change. With 100 Ohm between PE pin and chassis fuses will not melt fast enough to ensure personal safety. Please don't do any change unless being 100% confident to know how things should be done. For clarity: a metal casing or chassis is always connected directly to PE (when PE is used). No doubt about that!!!
I say this because you propose an outright dangerous change. With 100 Ohm between PE pin and chassis fuses will not melt fast enough to ensure personal safety. Please don't do any change unless being 100% confident to know how things should be done. For clarity: a metal casing or chassis is always connected directly to PE (when PE is used). No doubt about that!!!
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First, do you have a ground loop issue (ie, a hum)? If not, don't fix what's not broken.
If you do, get a piece of insulated wire. Connect one end to the ground binding post on your amp. Touch the other end wire to the case of your device. If the hum goes, you have solved your ground loop issue (although doing something to the case of a Class II device is technically messing with it's integrity and shouldn't be done).
The earth wire of your mains power is not appropriate for ground loop audio problems. It's there for electrical safety. Connecting it inappropriately to your electrical devices can actually make them dangerous in the event of an electrical fault.
If you do, get a piece of insulated wire. Connect one end to the ground binding post on your amp. Touch the other end wire to the case of your device. If the hum goes, you have solved your ground loop issue (although doing something to the case of a Class II device is technically messing with it's integrity and shouldn't be done).
The earth wire of your mains power is not appropriate for ground loop audio problems. It's there for electrical safety. Connecting it inappropriately to your electrical devices can actually make them dangerous in the event of an electrical fault.
Hi ! not particularly ... not completely noise free but i have also the tv on the same strip.
In the past i had a big loud hum trying to earth the chassis of an amp
I was shocked by the noise ... and i stopped using it considering that was old and not well mantained
you mean one of the two - black speaker posts ? some amps have a phono ground. No phono here.
Yes ! this i have understood. I would be altering the safety of the unity.
I see more and more amps class II ... now i understand that the problem with audio equipmente is that we have earth safety ground and audio ground. Many equipment have a ground lift switch.
I see. It seems like a proper sounding Class I device is a technical challenge ? nevertheless many amps are Class I i suppose. What is wrong with Class I ? i would be much more comfortable with that. Any live wire touching the case will shutdown the home voltage.
I have bought a little earth tester ... it seems that the ground is ok.
Quote: If you do, get a piece of insulated wire. Connect one end to the ground binding post on your amp.
Q: you mean one of the two - black speaker posts ? some amps have a phono ground. No phono here.
A: No. The red and black speaker binding posts are for the speaker cable only. Yes, the phono ground post is what I was referring to. If the amp doesn't have a phono input, it may not have a ground post, as earth/ground loops are a problem for turntables.
Again, I will state for the record (and not directed personally at you).
• If a device is Class II, then leave it as Class II.
• If a device is Class I, then leave it as Class I.
• Never try to convert one to the other.
Q: you mean one of the two - black speaker posts ? some amps have a phono ground. No phono here.
A: No. The red and black speaker binding posts are for the speaker cable only. Yes, the phono ground post is what I was referring to. If the amp doesn't have a phono input, it may not have a ground post, as earth/ground loops are a problem for turntables.
Again, I will state for the record (and not directed personally at you).
• If a device is Class II, then leave it as Class II.
• If a device is Class I, then leave it as Class I.
• Never try to convert one to the other.
Hi ! good. No phono here. If i will ever decide to listen to a turntable i will use and external phono preamp connected to the high level inputs in the line preamp. I like the phono preamp very close to the turntable.
Thanks again and message received loud and clear. By the way i am seeing more and more amps Class II. It seems a very popular design choice.
I really do no understand why because high quality amps have indeed th earth pin connected to the metallic chassis.
Strange. If i understand well voltage on the amp metallic enclosure would trigger the safety breaker ? that is good very good. I tend to touch things without thinking.
Don't think that Class I is better than Class II. They both meet rigorous safety standards so you are protected from electrocution appropriately if there is a fault. The Classes are about electrical safety. The electronics within those designs determine the quality of the device.
I don't agree as I have seen devices that apparently slipped through certification or the like. There is no mains voltage carrying electronic device in a metal casing that will be less safe when the floating case is connected to PE. I must add that I am no beginner in this field though.
Let me rephrase ... i meant that i would feel more comfortable with a unit that if there is any fault inside makes the breaker switch off the voltage on my home plant. Like any other short ... 😱
I have added IEC connectors to many, nearly all of my amp builds lately. I have chosen to float or not connect the 3rd prong / ground... in that, I do not want my speaker ground at the same potential as my microwave oven (as example).
Another thing in my case, I live in an older farm house in the country [with lax electrical code, in my area] where everything *is legal*, but it ultimately does not serve a purpose where I live and listen. *some of the newer circuit runs have grounding...
I added the IEC [primarily] to use my $$$ better shielded / heavier gauge AC cables, more than to facilitate grounding interests. Most vintage gear has (invisible) unseen fraying inside the captive cords... where the cord exits the chassis and has been flexed to eventual failure, possible leading to safety issues.
It makes little sense to wire my (personal built) amps with 10 / 12 gauge internal wiring on the transformers primary side, with wimpy stock captive on the outside.
Another thing in my case, I live in an older farm house in the country [with lax electrical code, in my area] where everything *is legal*, but it ultimately does not serve a purpose where I live and listen. *some of the newer circuit runs have grounding...
I added the IEC [primarily] to use my $$$ better shielded / heavier gauge AC cables, more than to facilitate grounding interests. Most vintage gear has (invisible) unseen fraying inside the captive cords... where the cord exits the chassis and has been flexed to eventual failure, possible leading to safety issues.
It makes little sense to wire my (personal built) amps with 10 / 12 gauge internal wiring on the transformers primary side, with wimpy stock captive on the outside.