Tube mic PSU with no safety ground

[Newmarket]

So there is no confusion, these mics will be used in a controlled studio environment, NOT live music venues. It is the owners decision on whether or not he wants them to be modified or remain original. He has chosen the later. While it may be the riskier choice and I believe he came to that decision for financial reasons, it it his choice and I have informed him of the risks.

Is this a commercial studio ?  I don't know about legislation as it applies in USA - but in UK / EU it seems likely that the owner would be putting himself in a legally vulnerable position in terms of exposing clients to a potentially dangerous situation. Similarly for any other users.
Consider that it would not pass PAT testing.
The position with electrical safety is reasonably clear. It is well defined by relevant legislation and bodies. It applies to all sectors - there's no 'get out' for audio because it's in someway 'special'.
If any mains powered equipment has a '2 wire' connection (ie no PE connection) then it MUST be of double insulated design. No exceptions.
For clarity: Any piece of equipment should be intrinsically safe whether or not it is attached to other equipment. Talk of providing a safety earth connection via audio cable screens etc is simply trying to evade the issue - the screen is unlikely to be of sufficient 'guage' to reliably conduct a fault current anyway.
wrt cost - how much would you be charging for the mains earth wiring modification ? More than the cost of a GCFI ?

I do, of course, also recommend the use of a GFCI / RCD device in the electrical installation.

 

[AusTex64]

Photo of my cable TV box attached... 2 conductor AC in, no safety ground. UL listed.

 

[ruffrecords]

Photo of my cable TV box attached... 2 conductor AC in, no safety ground. UL listed.

But it is double insulated and there are no  lethal voltages beyond the mains input. Not the same.

Cheers

Ian

 

[emrr]

Yes, but drop either one in the bathtub for same result.  It's kinda funny. 

 

[ruffrecords]

Yes, but drop either one in the bathtub for same result.  It's kinda funny.

UL does not insure against idiots. Even with a three prong, if some bozo cuts through the cable he can kill himself.

Cheers

Ian

 

[JohnRoberts]

UL does not insure against idiots. Even with a three prong, if some bozo cuts through the cable he can kill himself.

Cheers

Ian

I suspect UL does watch the behavior of "idiots" and adjusts safety standards based on ways they demonstrate that they can injure themselves. 

For example UL specifies hole size in chassis to prevent idiots from sticking their fingers through openings and touching electrically hot circuitry.  If enough idiots cut through energized line cords and hurt themselves they would probably specify armored line cords.  :

JR

 

[Matador]

Double insulated (IEC class 2) input devices are NOT THE SAME as what's being discussed here.  The cable box example above speaks to NOTHING about the safety of a tube PSU (even setting aside the issue that the tube PSU generates voltages well in excess of the mains voltage).

There are exactly zero reasons to not make this equipment safe.  Any tech that allows ungrounded equipment on their bench without performing the modification is (frankly) a fool.  If it were me and the original owner refused the modification I would have returned it and wished them luck.

Just because someone refuses to wear a seatbelt, doesn't mean they don't increase survivability of a crash.  Just because cars didn't have seatbelts in the 50's doesn't mean modern cars shouldn't have them.  Anyone who olds a 50's car should have seatbelts retrofitted.

 

[zamproject]

I'm 1000% with matador, and as I already say previously some post above, I don't understand why there is a debate about this...
Safety rules are  not opposable and no "advise" or "argument" offering options is acceptable in a public forum.

Connect your f***ing metal chassis to the safety earth, that's it...

Sorry...  :-\

Best
Zam

 

[gridcurrent]

not only is there a debate,
but there are no numbers suggesting any danger.
one of the most successful mastering rooms in Hollywood had EVERY piece of gear on a 2 wire cord,
and the gear with 3 wires were modified internally to lift the green wire.
hope your panties don't get too bunched up.

 

[Matador]

not only is there a debate,
but there are no numbers suggesting any danger.
one of the most successful mastering rooms in Hollywood had EVERY piece of gear on a 2 wire cord,
and the gear with 3 wires were modified internally to lift the green wire.
hope your panties don't get too bunched up.

What numbers would you like?  How about this: it takes only perhaps 10mA (or even less) to stop a heart.

That's the thing with unnecessary risks:  they aren't a problem right up until they are.  And modifying a grounded piece of gear to defeat safety grounds in the name of noise isolation:  well, here's the legal definition of 'recklessness' in California:

"[Recklessness is ] that a person knows that it is highly probable that his or her conduct will cause harm, and the person knowingly disregards this risk."

Seems apropos.

EDIT: here are some statistics. 

"Before the installation of Ground Fault Circuit Interrupters (GFCIs), which de-energize a circuit when they detect a ground fault, nearly 800 people died annually from household electrocutions. Now, less than 200 people die annually from household electrocutions."

 

[emrr]

one of the most successful mastering rooms in Hollywood had EVERY piece of gear on a 2 wire cord,
and the gear with 3 wires were modified internally to lift the green wire.

Were they running old-school ground scheme, with the racks themselves being the ground path, allowing mounting screws to dig into the rack ear paint for contact?  That was a thing, way back when. 

 

[zamproject]

Another "point" (not a criticism) but I see most of poster here are US based.
Keep in mind that this is a worldwide forum, safety earth and neutral scheme is not the same in every place aroud the world
you can't generalize ...

I hope for the floating mastering room that he never have a dead client...

Best
Zam

 

[emrr]

I hope for the floating mastering room that he never have a dead client...

He didn't say the room was floating.....