| Page 1 of 2 | 1 | 2 |
|
|
|
Running an amplifier unearthed
On Wed, 29 Nov 2017 13:09:28 +0000, Dave Plowman (News) wrote:
In article , D.M. Procida wrote: If you read uk.d-i-y, you may have seen a thread ("This appliance must be earthed") about Dutch mains sockets, which are often unearthed. If I plug a Cyrus 1 amplifier (which has an extremely metal case and a stern label saying "This appliance must be earthed") into an unearthed socket, do I risk death by electrocution, or worse, poorer sound quality? The warning simply means the construction doesn't conform to the EU requirements of a device with metal parts and no earth. Assuming it is in good condition, I doubt you'd get electrocuted by it with no earth. Noise figures as part of an installation may be poorer, though. It makes sense to hard earth the amplifier and utilise the 'interconnects's signal earths to provide safety earthing of the peripheral sources (TT. tuner, legacy optical disk player and tape deck (s)). However, take note that phono plugs can sometimes prove ineffective in earthing due to mismatches in the socket/plug dimensions so you need to take care in your choice of phono plugs if you're going to rely upon these interconnects to act as safety earths for your peripherals. One sure fire way to provide safety earthing on peripheral kit independent of signal earthing is to use a pair of 6A rated silicon diodes wired in anti-parallel with a 100 ohm resistor and a 100nF capacitor (all in parallel) in series with the safety earth connection with a 1A safety fuse in each individual peripheral's mains supply connection. Under normal operating conditions, the signal earths will short out the 100 ohm resistor and the diodes high impedance at sub 500mV peak voltages, effectively leaving the 'safety earth' connection in a state of 'disconnect' whilst still providing an effective safety earth in the event of a fault. One final note, it's good practice to power all of the components of a "separates" Hi-Fi setup from a single ring main socket[1] via a quality mains multi-socket extension lead or specialist connection strip. This neatly isolates ground loop currents that can occur when using different sockets on a ring main due to induced currents from heavy loads such as washing machines, toasters, kettles etc. [1] You can regard double/triple socket outlets (as well as adjacent single/double/triple socket outlets) as being effectively a single outlet in this case which can neatly do away with the need for a multi outlet mains lead extension socket. -- Johnny B Good |
Running an amplifier unearthed
In article ,
Johnny B Good wrote: One final note, it's good practice to power all of the components of a "separates" Hi-Fi setup from a single ring main socket[1] via a quality mains multi-socket extension lead or specialist connection strip. This neatly isolates ground loop currents that can occur when using different sockets on a ring main due to induced currents from heavy loads such as washing machines, toasters, kettles etc. I have a dedicated AV radial circuit here. With the earth for that going light back to the house earth. Not sure that bit makes any difference, though, but no big deal when installing it. -- *INDECISION is the key to FLEXIBILITY * Dave Plowman London SW To e-mail, change noise into sound. |
Running an amplifier unearthed
On Wed, 29 Nov 2017 18:20:16 +0000, Dave Plowman (News) wrote:
In article , Johnny B Good wrote: One final note, it's good practice to power all of the components of a "separates" Hi-Fi setup from a single ring main socket[1] via a quality mains multi-socket extension lead or specialist connection strip. This neatly isolates ground loop currents that can occur when using different sockets on a ring main due to induced currents from heavy loads such as washing machines, toasters, kettles etc. I have a dedicated AV radial circuit here. With the earth for that going light back to the house earth. Not sure that bit makes any difference, though, but no big deal when installing it. It shouldn't. Assuming you only have a single safety earth connection to the common signal ground return, the whole thing could be left to float at whatever induced mains voltage happens to occur (including half mains from filters or even a full contact to the live). It won't make any difference although I'd be rather leery of actually touching any of the kit if bringing your hand to within close proximity generates even the slightest hint of mains hum. -- Johnny B Good |
Running an amplifier unearthed
On Wed, 29 Nov 2017 19:04:32 GMT, Johnny B Good
wrote: On Wed, 29 Nov 2017 18:20:16 +0000, Dave Plowman (News) wrote: In article , Johnny B Good wrote: One final note, it's good practice to power all of the components of a "separates" Hi-Fi setup from a single ring main socket[1] via a quality mains multi-socket extension lead or specialist connection strip. This neatly isolates ground loop currents that can occur when using different sockets on a ring main due to induced currents from heavy loads such as washing machines, toasters, kettles etc. I have a dedicated AV radial circuit here. With the earth for that going light back to the house earth. Not sure that bit makes any difference, though, but no big deal when installing it. It shouldn't. Assuming you only have a single safety earth connection to the common signal ground return, the whole thing could be left to float at whatever induced mains voltage happens to occur (including half mains from filters or even a full contact to the live). It won't make any difference although I'd be rather leery of actually touching any of the kit if bringing your hand to within close proximity generates even the slightest hint of mains hum. These days most grounds are heavily compromised by EMC from switching power supplies coupled in through the Y1 capacitors. Hang enough of those on a single circuit and eventually you can even trip the RCD breaker. d --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
Running an amplifier unearthed
In article ,
Johnny B Good wrote: I have a dedicated AV radial circuit here. With the earth for that going light back to the house earth. Not sure that bit makes any difference, though, but no big deal when installing it. It shouldn't. Assuming you only have a single safety earth connection to the common signal ground return, the whole thing could be left to float at whatever induced mains voltage happens to occur (including half mains from filters or even a full contact to the live). It won't make any difference although I'd be rather leery of actually touching any of the kit if bringing your hand to within close proximity generates even the slightest hint of mains hum. Can you run that by me again? You can obviously get a potential difference between two earths when any current flows. Like say between the earth to a socket and the one to a light switch in the same room. -- *WHERE DO FOREST RANGERS GO TO "GET AWAY FROM IT ALL?" Dave Plowman London SW To e-mail, change noise into sound. |
Running an amplifier unearthed
In article ,
Don Pearce wrote: It shouldn't. Assuming you only have a single safety earth connection to the common signal ground return, the whole thing could be left to float at whatever induced mains voltage happens to occur (including half mains from filters or even a full contact to the live). It won't make any difference although I'd be rather leery of actually touching any of the kit if bringing your hand to within close proximity generates even the slightest hint of mains hum. These days most grounds are heavily compromised by EMC from switching power supplies coupled in through the Y1 capacitors. Hang enough of those on a single circuit and eventually you can even trip the RCD breaker. Which was the theory behind running my AV ground right back to the house earthing point, rather than CU earth. -- *Why don't sheep shrink when it rains? Dave Plowman London SW To e-mail, change noise into sound. |
Running an amplifier unearthed
In article ,
Brian Gaff wrote: Yes indeed, I was put of many moons ago from buying a Lecson system, you remember the coloured sliders pre amp and the cylindrical power amp, as touching the outside of the power amp while leaning on the radiator gave me one heck of a belt. I did not enquire as to quite why this happened but it seemed a trifle dodgy to me! Brian You can get a small potential difference between earths grounded at a common point when you measure well away from that point. Which is the principle of equipotential bonding in a bathroom. But a large one means something somewhere isn't right. -- *Filthy stinking rich -- well, two out of three ain't bad Dave Plowman London SW To e-mail, change noise into sound. |
Running an amplifier unearthed
Yes knowing the shop concerned I strongly suspect the lack of earthing issue
mentioned elsewhere in this thread had come unstuck. Its very easy to get a hum loop and feel that just unearthing one thing will fix it, but then forgetting that no earth is possible not good either if anything went wrong or just if a large capacitor is involved somewhere in the filtering. Back when I was a spotty youth the trick we used to play on the girls fitting components in the repair department was to leave a capacitor charged up with a couple of hundred volts on their benches. I'm sure you can imagine what tended to happen. Mind you there was one lady who seemed to be immune to shocks. Probably had dry skin. Brian -- ----- - This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please! "Dave Plowman (News)" wrote in message ... In article , Brian Gaff wrote: Yes indeed, I was put of many moons ago from buying a Lecson system, you remember the coloured sliders pre amp and the cylindrical power amp, as touching the outside of the power amp while leaning on the radiator gave me one heck of a belt. I did not enquire as to quite why this happened but it seemed a trifle dodgy to me! Brian You can get a small potential difference between earths grounded at a common point when you measure well away from that point. Which is the principle of equipotential bonding in a bathroom. But a large one means something somewhere isn't right. -- *Filthy stinking rich -- well, two out of three ain't bad Dave Plowman London SW To e-mail, change noise into sound. |
Running an amplifier unearthed
On Thu, 30 Nov 2017 12:00:07 +0000, Dave Plowman (News) wrote:
In article , Johnny B Good wrote: I have a dedicated AV radial circuit here. With the earth for that going light back to the house earth. Not sure that bit makes any difference, though, but no big deal when installing it. It shouldn't. Assuming you only have a single safety earth connection to the common signal ground return, the whole thing could be left to float at whatever induced mains voltage happens to occur (including half mains from filters or even a full contact to the live). It won't make any difference although I'd be rather leery of actually touching any of the kit if bringing your hand to within close proximity generates even the slightest hint of mains hum. Can you run that by me again? You can obviously get a potential difference between two earths when any current flows. Like say between the earth to a socket and the one to a light switch in the same room. Provided all the Hi-Fi kit is bonded together via the signal earths and only one point of connection to the signal earths is used to connect to the ring main earth, it won't matter how much voltage is induced into the mains earth. Indeed the whole lot can be left floating without detriment to the audio signals passing between the separate components, even to the point of having a connection (intentional or otherwise) to the mains live where the only detriment would then be to the health of anyone grounding such a high voltage to a real earth via their body. Some of the internal signal wiring might be less than completely screened from external electric fields which normally wouldn't be an issue until you introduce a source of high voltage gradient (240v 50Hz ac between you, at earth potential and the amplifier or TT wiring at 240v) hence my semi facetious remark about being leery of inducing a faint hum whenever you place a hand close to a less than completely screened piece of Hi-Fi kit. For line level signals, whatever minuscule currents might be induced into the local safety earths of tape decks, tuners and other line out sources will be way down in the noise. In any case, a lot of such kit is usually double insulated, allowing the screen connections (ground returns) to remain decoupled from all but the one and only connection point to the safety earth, typically the main amplifier. The one and only item of Hi-Fi kit that remains vulnerable to such hum induction is the old fashioned TT cartridge wired directly into a remote RIAA equalisation pre-amp located a metre or two away in the main amplifier. The proper way to deal with this problem is simply to install the RIAA pre-amp within the TT itself so that when the equalised signal from the TT has to negotiate the link to the main amplifier, it can do so at line level and appear as just another aux input signal labelled TT or 'Phono'. -- Johnny B Good |
| All times are GMT. The time now is 05:24 PM. |
|
Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.0.0
Copyright ©2004-2006 AudioBanter.co.uk