Show me a modern amplifier that is. It's called "double insulated" and it's normal. I've never seen a grounded consumer audio device.
My CD player has this - it's grounded via the RCA connectors. No internal chassis ground.
My MF amp on the other hand had a simply PE-> chassis but the amp/Heatsink PCB itself is centre tapped from the PCB. Funny that one of the PCB binding posts is earthed to the chassis and one poured trace is connected but doesn't connect to anything else.
I think you mixed 'class II' and 'class 2'.
Eg: some electrical dryers ( heaters) are 'Class II' ( and often ip24 when they have to be located in bathrooms). With the limitation of 'Class 2' they won't be of any use with at most 100w. 😉
'Class II' refers only to safety in my understanding: no metal parts can be in contact to metal case ( they are often enclosed design).
Eg: some electrical dryers ( heaters) are 'Class II' ( and often ip24 when they have to be located in bathrooms). With the limitation of 'Class 2' they won't be of any use with at most 100w. 😉
'Class II' refers only to safety in my understanding: no metal parts can be in contact to metal case ( they are often enclosed design).
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Funny thing about “ground.”
In nearly all circuit breaker panels, “ground”and “neutral” are bonded.
On a two-wire plug ONE wire is “hot” (I remember this by the simple sexist mnemonic “hot little one”), the other connects to neutral in the socket, which in the US is the white wire, which goes to the panel, which connects to the green ground wire which connects to an 8-10 foot rod (or two) coated with copper driven into the earth by the house (in old days it would be tied to the incoming water pipe).
I would think a “ground loop” would be easier to make with the third wire connected, but since they’re both connected at “earth” this shouldn’t matter.
I was only ever an apprentice electrician’s helper (39 years ago), been a ham radio guy for almost ten years, amateur electronic hobbyist since around 1968, and I still don’t fully understand the nuances of “ground” - maybe obviously to those far more educated on the matter.
Just my two cents.
In nearly all circuit breaker panels, “ground”and “neutral” are bonded.
On a two-wire plug ONE wire is “hot” (I remember this by the simple sexist mnemonic “hot little one”), the other connects to neutral in the socket, which in the US is the white wire, which goes to the panel, which connects to the green ground wire which connects to an 8-10 foot rod (or two) coated with copper driven into the earth by the house (in old days it would be tied to the incoming water pipe).
I would think a “ground loop” would be easier to make with the third wire connected, but since they’re both connected at “earth” this shouldn’t matter.
I was only ever an apprentice electrician’s helper (39 years ago), been a ham radio guy for almost ten years, amateur electronic hobbyist since around 1968, and I still don’t fully understand the nuances of “ground” - maybe obviously to those far more educated on the matter.
Just my two cents.
Ground is arbitrary. Circuit and signal ground are, anyway.
Take a normal 6SN7 tube circuit. Normally, you ground the cathode and put +250V on the plate. You could connect the plate to ground and connect cathode to -250V instead though, and the circuit still works. It's the same power supply, all you did is change the reference point of the ground WRT the PSU.
Protective Earth ground isn't arbitrary 🙂 but it's also not required for double insulated devices.
Every consumer electronic device in my place have 2 wire power cords. That goes for phone chargers, the tape deck, minidisc, turntable, tuner, television,"cable" modem, PVR etc.
Only appliances are grounded here. Microwave oven, toaster oven, kettle etc. My air conditioner also includes a GFI in the plug.
Computers are also grounded but that has less to do with safety and more to do with RFI/EMI suppression as far as I know. Otherwise, they would make plastic computer cases 🙂
Take a normal 6SN7 tube circuit. Normally, you ground the cathode and put +250V on the plate. You could connect the plate to ground and connect cathode to -250V instead though, and the circuit still works. It's the same power supply, all you did is change the reference point of the ground WRT the PSU.
Protective Earth ground isn't arbitrary 🙂 but it's also not required for double insulated devices.
Every consumer electronic device in my place have 2 wire power cords. That goes for phone chargers, the tape deck, minidisc, turntable, tuner, television,"cable" modem, PVR etc.
Only appliances are grounded here. Microwave oven, toaster oven, kettle etc. My air conditioner also includes a GFI in the plug.
Computers are also grounded but that has less to do with safety and more to do with RFI/EMI suppression as far as I know. Otherwise, they would make plastic computer cases 🙂
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100 VA continuous apparent power is an average power. It could be as much as an 800 watt audio amp, since operating conditions for audio amps (even pro amps) are now defined as 1/8 power with pink noise rather than sine wave. This goes for both current draw from the wall and output wiring requirements. Because the signal represents music, which it would actually be used with.
This has resulted in making power supplies weaker and weaker over the years because the bar isn’t as high as the old 1/3 power sine wave preconditioning requirement. Which made amps “too heavy” for most consumer use, and put a cap at around 800 watts on the size that you could legally plug into a standard 120 volt outlet. In the old days, the Peavey CS-800 was as big as you could make it - since it draws 15 amps off the wall when both channels are putting out 400 watts into 4 ohms sine wave. They wanted class I wiring back in those days, since it could put out 800 VA into a 70 V line (With the music so distorted you can’t even tell what song is playing). Real would use was always much less, around half the current draw, and less than 100 VA output. The same is true of any other amp capable of the same power. Now useage conditions and safety requirements more closely align. Whether or not you like today’s woosy power supplies is another matter - but you can build a boat anchor amp if you wanted to. They are harder to buy new now.
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https://www.ranecommercial.com/legacy/note151.html
Most of the diagrams are from OTT electromagnetic compatibility engineering, which I would recommend if you want to know more. if you can avoid a protective earth connection in an unbalanced device it will always be preferable for noise.
Most of the diagrams are from OTT electromagnetic compatibility engineering, which I would recommend if you want to know more. if you can avoid a protective earth connection in an unbalanced device it will always be preferable for noise.
I automatically thought this was about a DIY amp, since we're on duyAudio... commercial devices are mostly double isolated and don't need the safety earth connection.
Can someone explain is simple words what exactly does it mean that PSU or amp is "double insulated" ?
As opposed to (I guess) "single insulated" ?
As opposed to (I guess) "single insulated" ?
"A Class II or double insulated electrical appliance uses reinforced protective insulation in addition to basic insulation. Hence, it has been designed in such a way that it does not require a safety connection to electrical earth (ground).
The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having at least two layers of insulating material between live parts and the user, or by using reinforced insulation.
In Europe, a double insulated appliance must be labelled Class II or double insulated or bear the double insulation symbol: ⧈ (a square inside another square). As such, the appliance should not be connected to an earth conductor because the high-impedance casing will cause only low-fault currents that are unable to trigger the fusible cut-out.[1]
Insulated AC/DC power supplies (such as cell-phone chargers) are typically designated as Class II, meaning that the DC output wires are isolated from the AC input. The designation "Class II" should not be confused with the designation "Class 2", as the latter is unrelated to insulation (it originates from standard UL 1310, setting limits on maximum output voltage/current/power)."
https://en.wikipedia.org/wiki/Appliance_classes
The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having at least two layers of insulating material between live parts and the user, or by using reinforced insulation.
In Europe, a double insulated appliance must be labelled Class II or double insulated or bear the double insulation symbol: ⧈ (a square inside another square). As such, the appliance should not be connected to an earth conductor because the high-impedance casing will cause only low-fault currents that are unable to trigger the fusible cut-out.[1]
Insulated AC/DC power supplies (such as cell-phone chargers) are typically designated as Class II, meaning that the DC output wires are isolated from the AC input. The designation "Class II" should not be confused with the designation "Class 2", as the latter is unrelated to insulation (it originates from standard UL 1310, setting limits on maximum output voltage/current/power)."
https://en.wikipedia.org/wiki/Appliance_classes
Having ground from rectifier connected to the metal case of the amp qualifies it as "single" or "double" insulated?
Or perhaps "0 insulated" ?
Or perhaps "0 insulated" ?
0 insulated would be like connecting the line to the chassis.
The point is not getting a shock from the line. Single insulation does this by earthing the metal chassis. In my amplifier designs, the chassis is also connected to the rectifier negative along with Earth.
The point is not getting a shock from the line. Single insulation does this by earthing the metal chassis. In my amplifier designs, the chassis is also connected to the rectifier negative along with Earth.