Hello, I've been following the forum for a long time but never joined it;
Now I'm here to ask advice for a problem I'm having on a Objective 2 amp.
(The kit is the one form Head 'n' Hifi)
 
I assembled all the circuit correctly and successfully passed all the test (even the advanced ones) that NwAwGuy suggest on his blog)
 
The amp seems to work just fine, there's only a strange thing I noticed:
When I plug in the AC coax into the amp, if the outer layer of the plug touches the front cover while inserting it, it makes an electrical connection with it and I get a tiny blue electric arc, a 'zap'. Isn't it strange?
 
I connected the ground to the case from pin 1 of the input jack. If I disconnect the ground I don't get the zap.
 
Also I noticed the AC wall adapter given in the kit doesn't have the center pin (EU plug) that's usually found in grounded devices.
What do you think?
 
 
Thank you in advance.

I'm still trying to find the strange part.
 
Plug the power supply into the amp before plugging it into the wall.
And.
If it meets local safety standards or not is the only concern with a sealed AC to AC adapter (transformer) that is housed in an insulated enclosure not having a safety ground.
Even if it had one the safety ground would not connect to the amplifier so
...

I think it's to do with the socket and equipment being ungrounded. You can get really strange phenomena with stuff like that. I don't really have the physics explanation for it but when I plug my computer adapter into certain power outlets, usually non grounded ones, the whole aluminum body of my laptop gets a sort of "vibrating" feel to it, but only when I brush my hands over it.
 
As you have batteries in your O2 as well, that's a potential source for building up a static charge in the circuits somewhere. If the difference in charges between the plug and the housing is large enough, you'll get a spark. Sorry if I'm stating the obvious but like MisterX, I can't really see the strange part here. At least I don't think there's a problem with your build.

Yeah, i noticed that strange vibrating feeling too! (With a 2014 retina macbook pro)
 
I followed your suggestions and first plugged the coax in, then the wall adapter, and never had any problems since.
I was worried that those sparks could have damaged the amp but I went through the NwAvGuy test procedure again and everything was ok.
 
I was worried that it was a building problem as the metal case is really close to the outer part of the plug, even when it's already plugged in, maybe with a little bit of random jiggling it could still  get a spark. Do you think that it could damage the components?
 
No one ever noticed this phenomenon with an O2?

I have noticed the "phenomenon", too.

The plug touching the front panel while plugged in won't damage anything. Both the enclosure and the outer part of the plug are wired to gnd of the amp. The spark is most likely caused by the capacitors in the amp getting charged. You can try pulling the ac cable out and plugging right back in and you'll notice that the spark is much less violent than when you have discharged the capacitors before plugging it in. (Discharge the caps by turning the amp on without the ac connected)
The thin anodizing on the aluminium is non-conductive which also makes it spark worse.

Thank you so much for the explanation. Yes, I as well noticed the spark is lesser if I follow your procedure, which brought me to think about the caps too. So, everything is fine as it is. The amp works nicely.