Why Do All Arcam Units (and Maybe Others) Have Only Two-Prong Power?


I've always been curious about this.  I used to own gear in their Alpha line and then FMJ.  They have always had just two prongs on the back of the unit for the power cord.  How are they grounding?  I'm not an EE, but I understand how balanced signals and electrical grounding works.  Are they not using a fully balanced design inside?
jwseitz
@ jwseitz


Because Arcam spent the additional cost and used double insulated AC power wiring.
Class II (with Roman numerals) refers to power supplies with either a double or
reinforced insulation barrier between the input and the output. Class II supplies do
not rely on an earth connection to protect against shock hazard. Many cell phone
chargers and laptop power supplies are Class II.
Many external power supplies are also Class II, having just a Line and Neutral AC
input without a ground connection.

A Class II power supply rating label will show this symbol:
https://www.heliosps.com/wp-content/uploads/sites/5/2017/09/application-notes-class2-insulation.pdf


Class II Class II symbol

A Class II or double insulated electrical appliance is one which 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).

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#Class_II


EGC (Equipment Grounding Conductor) is not used or needed.

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Grounding Myths

"Electromagnetic Compatibility Engineering" by Henry Ott

3.1.7 Grounding Myths

More myths exist relating to the field of grounding than any other area of electrical engineering. The more common of these are as follows:

1. The earth is a low-impedance path for ground current. False, the impedance of the earth is orders of magnitude greater than the impedance of a copper conductor.

2. The earth is an equipotential. False, this is clearly not true by the result of (1 above).

3. The impedance of a conductor is determined by its resistance. False, what happened to the concept of inductive reactance?

4. To operate with low noise, a circuit or system must be connected to an earth ground. False, because airplanes, satellites, cars and battery powered laptop computers all operate fine without a ground connection. As a matter of fact, an earth ground is more likely to be the cause of noise problem. More electronic system noise problems are resolved by removing (or isolating) a circuit from earth ground than by connecting it to earth ground.

5. To reduce noise, an electronic system should be connected to a separate “quiet ground” by using a separate, isolated ground rod. False, in addition to being untrue, this approach is dangerous and violates the requirements of the NEC (electrical code/rules).

6. An earth ground is unidirectional, with current only flowing into the ground. False, because current must flow in loops, any current that flows into the ground must also flow out of the ground somewhere else.

7. An isolated AC power receptacle is not grounded. False, the term “isolated” refers only to the method by which a receptacle is grounded, not if it is grounded.

8. A system designer can name ground conductors by the type of the current that they should carry (i.e., signal, power, lightning, digital, analog, quiet, noisy, etc.), and the electrons will comply and only flow in the appropriately designated conductors. Obviously false."

Henry W. Ott

Who is Henry Ott?
http://www.hottconsultants.com/bio.html


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Thank you for the answers.  I don't know why I never got a notification that there were any...

So is it possible for Class II units to have "fully balanced" topology inside?  Are Arcams?

Because it sounds better.  A really easy test.  Purchase a three prong to two prong cheater plug and isolate your amp.  I actually use one for DAC also.  Much tighter bass and a clearer background.  There is a safety factor but your amp isn't a skill saw and to me the sound benefits outweighed the tiny risk of a shock.

Violating the ground of something designed to be grounded can kill you.  Just saying.

 

I actually experienced the opposite.  I had two-prong outlets in an older home before building new.  When I ran my same system/amp again in the new place on a grounded circuit it was much better sound.

Violating the ground of something designed to be grounded can kill you.  Just saying.

I could be struck by an asteroid too.  Did you try a two prong plug into the new place?  How did it sound?

Look at your toaster.  How many prongs does its plug  have.  A toaster would be a lot more dangerous to a user than modern amp.