Good article here on the safety aspects of balanced power-

www.soundonsound.com/sos/nov06/articles/crosstalk_1106.htm

+1
Safety first.

Happy anniversary
No presents?

Bugger, bloody typical. Yes sir, no problem sir 

Dave

Its not fundamentally different to the one on HFS, except to include links to sites explaining the way an RCD works, and its dependence on a differential current in the windings round its sensor transformer core, the way a circuit breaker works, the combination of both in an RCBO, and the nature of the current that flows in a primary, regardless of where the current is flowing in the secondary (as evidenced in the Pip switch light wiring I quoted on HFS, and will repeat here).  I might add a video'd demonstration if the pro's are up for it.  But i want to sit down to it with a clear head to keep rambling to a minimum, and i am about to go out for dinner on my anniversary.  I don't think insurance is an issue.  Anything else and I am pretty happy with the technical support in my corner.  I'm not trying to be clever.  I'm trying to benefit other forum users with the technical expertise I have the great good fortune to have access to, and the generosity of spirit of those experts prepared to take the time to explain things. 

Hi Dave

The posts were on my ramblings but there is so much aggressive thread cleansing going on over on HFS at the moment, that may not help you much.  When I post here regarding mains it will be on MartinT's mains thread.  For as long as its there, the link is HFS comments re BPO's

Richard Dunn has edited out my comment that I was not criticising NVA, where I noted that their designs were more in the nature of NVA badging of other peoples designs.  I am not aware (he did not say) he has anythng new or different proposed for the NVA balanced power output - just that they are made, and he would be doing an NVA version.  I assumed not different to most others on the market, and Gazjams with a true earth on the output, but he appears to be referencing a floating earth, which clearly could not be used with any class 1 device, since a class 1 device needs a path to true earth.  Anyway, enough NVA

Honest guv, I will deal with the mains safety aspects on the mains thread on this forum, but in the meantime I will post here the link I posted on HFS explaining a bit about safety Sound on Sound Balanced Power safety

This accords with what my electrician client told me (he installs electrics and PAT tests and certifies operating theatres), and the explanations Owen has supplied.

Back on topic for this thread, as a throw-away comment at the end of our discussion Owen said "They don't work you know.  Not as this bloke  describes".  Now bear with me while I try to share this.  Any competent engineers who can do better on the maths, please chip in and explain to us all.  I have used up my Owen allowance until I can ply him with red wine in September.  He doesn't want anything to do with forums, and it was above and beyond agreeing to teach me on a safety point.  Why don't BPO's work?  Well, as Richard Dunn stated - they are the equivalent of balanced connections on interconnects.  There is no differential amplifier involved - the incoming mains "signal" is split into 2 balanced signals along the wire from the BPO to the device (ie power amp etc) by virtue of taking a centre tap on the secondary to ground.  The incoming "signal"  is split into 2 signals - a 120v copy of the input, and a -120v copy 180 degrees out of phase.

Like a true balanced connection for interconnects, any (most in most circumstances) noise added to the connection between the BPO and the device (power amp) is cancelled on output when the "signals", strictly the differential signal, are rectified back by the circuit completion in the device (power amp).  So Signal A (positive) and signal -A (negative) are 180 degrees out of phase.  Any noise ADDED TO THEM is added equally and in phase, and is therefore present on both A and B but 180 degrees out of phase.  So the connections result in the following

So output = (A+ noise) - (-A + Noise), which in turn = A+Noise + A-Noise= 2A.  In our case (120v +noise) - (-120v + noise) = 240v.  The noise is cancelled (noise-noise=0)

But which noise?  There are 2 noises.  N1 is noise on the input (grunge on your domestic mains). N2 is noise affecting the cable connecting the BPO to the device (power amp).  N1 is part of the signal.  So the equation reads

(A + N1 +N2) - (-A -N1+ N2), and this in turn is A+N1 +N2 + A + N1 -N2 = 2A+2N1 (N2-N2 cancels to zero)

The noise on the mains coming into the BPO is not cancelled by the balanced transmission of that incoming mains and its noise to the device.  But no new noise will be added between the BPO and the device (big deal - the tiny bit that might be is only the equivalent to the extra noise coming from the wall socket to the BPO anyway)

Think about it - it is identical to balanced interconnects.  They enable a very tiny signal to be carried over long distances in a studio without any new noise being added by that long connection, but it doesn't strip out any noise that was on the signal in the first place.  Enough for one post.  Next post I'll talk about what an objectivist should measure, if you are going to take measurements



Edit - a bit of relabelling of variables - I was using 3 labels for the same thing - very confusing

If anyone wants to have a go about the design Gary is using, have a go at me, it's my design, not Gary's, so the blame lies with me!

Yes, please return to discussions of regenerators here. There is another thread running for mains safety.