Post No Bills Posted March 21 Posted March 21 I just bought 10AWG earthed power cables for my amps and noticed that my amps are double insulated and don’t require an earth. There isn't any earth prong on the amps. Is it safe to use the earthed power cables on these since the earth isn‘t connecting to the amps?
aussievintage Posted March 21 Posted March 21 1 hour ago, Post No Bills said: I just bought 10AWG earthed power cables for my amps and noticed that my amps are double insulated and don’t require an earth. There isn't any earth prong on the amps. Is it safe to use the earthed power cables on these since the earth isn‘t connecting to the amps? I don't know what type of plug/sockets you have but surely ,the earth will simply not connect to anything.
andyr Posted March 21 Posted March 21 (edited) 3 hours ago, Post No Bills said: I just bought 10AWG earthed power cables for my amps and noticed that my amps are double insulated and don’t require an earth. There isn't any earth prong on the amps. Is it safe to use the earthed power cables on these since the earth isn‘t connecting to the amps? YES! Note: an issue with 2-wire mains cord items (so-called "double insulated") ... is that as there is no mains earth wire to attach to the case ... the case doesn't provide a totally effective shield for RFI. Same holds true for components which have an external DC supply (whether LPS ... or SMPS). So they really should have an earth terminal on the case which can then be connected to another component which is case-earthed. Edited March 21 by andyr 1
FR DRew Posted March 21 Posted March 21 It does of course mean that you may be paying for earth conductors hand rolled on the thighs of virgin Sardinians for no net gain... 1 1
pete_mac Posted March 21 Posted March 21 11 minutes ago, FR DRew said: It does of course mean that you may be paying for earth conductors hand rolled on the thighs of virgin Sardinians for no net gain... Would you… er… mind sending me a private message regarding where I can source said cables? Asking for a friend. 2
aussievintage Posted March 21 Posted March 21 12 minutes ago, FR DRew said: It does of course mean that you may be paying for earth conductors hand rolled on the thighs of virgin Sardinians for no net gain... But that would be true even if his equipment had an earth pin.
FR DRew Posted March 21 Posted March 21 Interestingly, on another platform I've been speaking with one of the engineers and service techs from Krell. Given the effort they put into power supplies, you can guess what his opinion on mega dollar power leads is...
audiofeline Posted March 22 Posted March 22 If a device is double-insulated it should only accept a two-wire lead, it shouldn't be fitted with a 3-wire socket. If it has the 3-wire socket and is marked as double-insulated it won't be meeting Aust. electrical standards. 1
rocky500 Posted March 23 Posted March 23 On 22/03/2025 at 6:23 PM, audiofeline said: If a device is double-insulated it should only accept a two-wire lead, it shouldn't be fitted with a 3-wire socket. If it has the 3-wire socket and is marked as double-insulated it won't be meeting Aust. electrical standards. Sounds like the manufacturer might have messed up there but still will be ok to plug a 3 wire cable in there as the earth will just not be connected?
andyr Posted March 23 Posted March 23 10 hours ago, rocky500 said: Sounds like the manufacturer might have messed up there but still will be ok to plug a 3 wire cable in there as the earth will just not be connected? Exactly! 1
Bronal Posted Thursday at 06:56 AM Posted Thursday at 06:56 AM Some years ago I bought a pair of used Carver Black Beauty valve power amps. When they arrived, I noticed that they had two-pin power sockets, although a standard three-pin power cable would fit but with no earth connection. I took them to Bill Crampton for a check-over and some minor modifications, as I normally did with secondhand equipment, before he moved away from Canberra, and sought Bill's advice about earthing. Bill told me there was no evidence that they were double-insulated in the conventional manner and recommended that they be earthed to the chassis, which was quite easy to do. Bill was concerned that there was no direct earthing, despite the fact that the amps had metal cases. I have always been fastidious about this myself and have often wondered about Japanese equipment, which also used to be two-pin. What happens if it develops a short? I asked this question before on SNA and surprsingly no one seemed to know the answer. Does it 'earth' via neutral, like US, Australian and some European equipment of the 1950s?
aussievintage Posted Thursday at 07:25 AM Posted Thursday at 07:25 AM 21 minutes ago, Bronal said: I have always been fastidious about this myself and have often wondered about Japanese equipment, which also used to be two-pin. What happens if it develops a short? I asked this question before on SNA and surprsingly no one seemed to know the answer. Does it 'earth' via neutral, like US, Australian and some European equipment of the 1950s? A short from where to where? A short from active to neutral will blow the fuse. A short from Active to case may electrocute you if you touch it whilst grounded. A short from neutral to case will do nothing much. Trip earth leakage maybe? If by "'earth' by neutral", you mean the case is connected to neutral, that would be considered unsafe. Nevertheless, earth and neutral are joined together at your switchboard, so maybe not disastrous. If your neutral link at the switchboard was faulty and a fault somewhere in the distribution system developed, the neutral AND your case could have it's potential raised and present a hazard I suppose. Just thinking out loud. It is not the thing to do.
audiofeline Posted Thursday at 09:27 AM Posted Thursday at 09:27 AM 2 hours ago, Bronal said: ... I have always been fastidious about this myself and have often wondered about Japanese equipment, which also used to be two-pin. What happens if it develops a short? I asked this question before on SNA and surprsingly no one seemed to know the answer. Does it 'earth' via neutral, like US, Australian and some European equipment of the 1950s? FYI, here is an explanation of Class I (earthed) and Class II (double-insulated) electrical equipment, based on Aust. electrical standards. https://www.pat-testing-training.net/articles/class-I-vs-class-II-electrical-equipment.php
andyr Posted Thursday at 09:40 AM Posted Thursday at 09:40 AM 8 minutes ago, audiofeline said: FYI, here is an explanation of Class I (earthed) and Class II (double-insulated) electrical equipment, based on Aust. electrical standards. https://www.pat-testing-training.net/articles/class-I-vs-class-II-electrical-equipment.php Sorry, Rob - I'm afraid I'm not going to spend any of the time I have left on this earth reading that article ... but I simply wonder why on earth all mfrs don't use a 3-wire mains cord - whether captive or IEC - when the result of this is that the case doesn't provide as good an RFI shield as it would if it was earthed? Saving a few dollars is all I can come up with.
rocky500 Posted Thursday at 10:13 AM Posted Thursday at 10:13 AM 31 minutes ago, andyr said: Sorry, Rob - I'm afraid I'm not going to spend any of the time I have left on this earth reading that article ... but I simply wonder why on earth all mfrs don't use a 3-wire mains cord - whether captive or IEC - when the result of this is that the case doesn't provide as good an RFI shield as it would if it was earthed? Saving a few dollars is all I can come up with. I would of thought to try and minimize earth loops/hum maybe? 1
aussievintage Posted Thursday at 11:06 AM Posted Thursday at 11:06 AM 46 minutes ago, rocky500 said: I would of thought to try and minimize earth loops/hum maybe? Yep. It's a basic problem with consumer equipment connected with RCA connectors, all earthed at each piece of equipment. @andyr Everything would be much better if everything was unearthed with signal grounds isolated from the case, and we provided the the single earth point, and connected the cases (if made of metal), and the signal ground, to the single earth point. Trouble is, in terms of safety, you can't trust the great masses out there to do it properly. Double insulated equipment is a step towards avoiding the problem.
Bronal Posted Thursday at 11:33 PM Posted Thursday at 11:33 PM 16 hours ago, aussievintage said: A short from where to where? A short from active to neutral will blow the fuse. A short from Active to case may electrocute you if you touch it whilst grounded. A short from neutral to case will do nothing much. Trip earth leakage maybe? If by "'earth' by neutral", you mean the case is connected to neutral, that would be considered unsafe. Nevertheless, earth and neutral are joined together at your switchboard, so maybe not disastrous. If your neutral link at the switchboard was faulty and a fault somewhere in the distribution system developed, the neutral AND your case could have it's potential raised and present a hazard I suppose. Just thinking out loud. It is not the thing to do. Please forgive me, for I have sinned. I should have realised that you need at least HSC-level knowledge of electronics and related terminology to enter into any conversation here. Seriously, I thought it was quite clear what I meant. I meant 'what if the chassis goes live'. Isn't earthing supposed to deal with that? If it doesn't, then what IS it supposed to do? 14 hours ago, audiofeline said: FYI, here is an explanation of Class I (earthed) and Class II (double-insulated) electrical equipment, based on Aust. electrical standards. https://www.pat-testing-training.net/articles/class-I-vs-class-II-electrical-equipment.php Doesn't that article relate to UK standards (which may well be the same as ANZ standards)? Have these standards been universally adopted? 1
bob_m_54 Posted Friday at 12:05 AM Posted Friday at 12:05 AM 14 hours ago, andyr said: Sorry, Rob - I'm afraid I'm not going to spend any of the time I have left on this earth reading that article ... but I simply wonder why on earth all mfrs don't use a 3-wire mains cord - whether captive or IEC - when the result of this is that the case doesn't provide as good an RFI shield as it would if it was earthed? Saving a few dollars is all I can come up with. To save you reading the article, the reason is explained about half way down the page. Quote A significant advantage of Class II construction is that it does not rely on the earthing provided by the building's wiring for protection. Even if the earthing in the building's wiring is faulty or non-existent, Class II equipment still provides reliable protection against electric shock. 1 1
aussievintage Posted Friday at 12:09 AM Posted Friday at 12:09 AM 30 minutes ago, Bronal said: Please forgive me, for I have sinned. I should have realised that you need at least HSC-level knowledge of electronics and related terminology to enter into any conversation here. Seriously, I thought it was quite clear what I meant. I meant 'what if the chassis goes live'. Isn't earthing supposed to deal with that? If it doesn't, then what IS it supposed to do? You actually asked - what if it develops a short? Not all shorts make the chassis go live, even if it is not earthed. Even if the active wire shorts to chassis, chances are that one of your interconnect cables will save you by finding a path to earth and blowing the fuse or tripping the earth leakage, but don't rely on it. 1
bob_m_54 Posted Friday at 12:35 AM Posted Friday at 12:35 AM 59 minutes ago, Bronal said: Seriously, I thought it was quite clear what I meant. I meant 'what if the chassis goes live'. Isn't earthing supposed to deal with that? If it doesn't, then what IS it supposed to do? In the case of Class II equipment, it is extremely unlikely for the "chassis to go live" due to the enhanced safety of double, or reinforced insulation between live parts and the chassis. That's the whole point of Class II equipment. Safety is designed into the equipment and doesn't need to rely an an external earth system. 1
andyr Posted Friday at 01:06 AM Posted Friday at 01:06 AM 29 minutes ago, bob_m_54 said: In the case of Class II equipment, it is extremely unlikely for the "chassis to go live" due to the enhanced safety of double, or reinforced insulation between live parts and the chassis. That's the whole point of Class II equipment. Safety is designed into the equipment and doesn't need to rely an an external earth system. So 'Safety' is promoted - at the expense of function? (Better RFI shielding from the case being earthed.)
audiofeline Posted Friday at 01:33 AM Posted Friday at 01:33 AM Regarding the link to the article I posted explaining Class I and Class II electrical equipment... 1 hour ago, Bronal said: Doesn't that article relate to UK standards (which may well be the same as ANZ standards)? Yes, you are correct, it is a UK article, I thought it was Australian page. However, the content is consistent with what I recall being taught several years ago when doing a test+tag course, I think there is a commonality in international standards (which makes sense given international manufacturing and marketing). 1
aussievintage Posted Friday at 01:50 AM Posted Friday at 01:50 AM 41 minutes ago, andyr said: So 'Safety' is promoted - at the expense of function? (Better RFI shielding from the case being earthed.) Of course. Have you ever worked in industry? This is the way of life when people's lives are in jeopardy - always. Be thankful we have these safety regs.
andyr Posted Friday at 03:20 AM Posted Friday at 03:20 AM 1 hour ago, aussievintage said: Of course. Have you ever worked in industry? This is the way of life when people's lives are in jeopardy - always. Be thankful we have these safety regs. No, I haven't worked on a production line, av. In that environment - sure, safety regs are of paramount importance. This thread is about home electronics items.
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