Well I've just had my own 'Zen moment'. I'm gonna try the following:

electricity meter -> dedicated consumer unit -> PurePower2000 regenerator -> 5KVA balanced transformer (house PE on input, dedicated PE on output) -> 8-way distribution block

Don't think I really need the 15KVA isolation transformer. Anyone want one? It's 120Kg though!

Mani.

I think this would be prudent. As I said, in one of the transformers I received, the input/output grounds were both conneced, in the other they were not. Which did they mean? I don't know. But if it's the latter, there had better be a connection made pronto if there's a serious fault in the appliance.


No it didn't, which was a pain. But I intended to connect the transformer's output ground to my dedicated PE anyway so wasn't too bothered.

I've just checked how loudly the 5KVA hums, and it's actually fairly quiet with a low load. It get's considerably louder with my ~1400W RMS though.

Mani.

OK, I've made some measurements between my dedicated PE (measured by electrician as <5Ω resistance to earth) and my house PE (no idea of what this resistance to earth is):

1) with small load (only NOS1 switched on):
- resistance = 2.5MΩ
- DC = 0.25V
- AC = ~0.6V (varies a little, not totally constant)

2) with ~1000W load (Sauermann amps switched on)
- resistance = 2.5MΩ
- DC = 0.25V
- AC = ~0.6V

No, not a 'copy and paste' mistake, but absolutely no difference whatsoever.

In case it's importanct, the whole AC chain here is: house electricity meter -> dedicated consumer unit -> 15KVA isolation transformer -> 5KVA balanced transformer -> PurePower2000 regenerator -> 8-way distribution unit

The dedicated PE consists of: ionic grounding rod and a star earthing arrangement to all components (including PC)

The PurePower2000 uses a switching power supply, which I assume kicks a lot of noise back into the AC feeding it. But the AC feeding it is balanced, which I suspect helps.

Mani.

Hey Peter, I think even Einstein would need some time to figure this post out... I'll do my best later this evening.

Mani.

I'm sure you're right. I remember a while ago, with the PC, NOS1 and amp all connected to the same PE, I tried connecting the chassis of the PC to PE too. And guess what? The sound totally changed. At first, I thought it was an improvement, but over a period of time I found it fatiguing. I now think I was getting false detail and brightness through a ground loop somewhere. Or maybe the chassis was now acting as an RF antenna? Who knows...

Mani.

Hi Nick, I think there is an audible hum from the unit, but sitting as it does in the cellar I don't really pay much attention to it. What I do know is that it's much quieter than the 15KVA 'yacht hull isolation' transformer sitting below it.

There is one thing I'd do if I were you though. AirLink claims, "The Balanced  Power Supply creates a new ground called a derived ground, that decouples equipment connected to it from the circulating ground currents in the rest of the house wiring.  It also provides one common ground reference for all the equipment connected to it."

One of my 5KVAs has the input ground connected to the output ground. The other has the two grounds isolated, although even in this case, there is still a ~6MΩ resisitance between them. Now I have no idea how you 'derive' a new ground from the house ground, but even with my dire knowledge of electronics I know that this simply cannot be the case if the input and output grounds are connected together. It seems to me that someone at AirLink isn't quite sure how to do it either, so I'd check with them before ordering. HTH.

I won't be able to test various power configurations until some new junction boxes that I've ordered come through. But I'll let you know what I find as soon as I get them.

Mani.

Hi Stefano. Audible in a good way or bad? The main criticism of transformers is that they can sometimes seem to compress dynamics and make the sound a bit dull/lifeless. Did you find this?

Mani.

Hey Nick, I've just checked and my Airlink 5KVAs have these installed as standard - one on the input, one on the output. HTH.

Mani.

This won't be an issue for me as I will now use a PurePower regenerator to feed all the components. This will take the balanced +115V/-115V and reconvert it back to 0/+230V. If there is a fault condition on either phase feeding it, the PP will simply kick into battery mode.

But the isolation- and/or balanced-trannies will not be for nothing even with a PP in place. Other PP users have reported that the better the incoming AC into the PP, the better the sound. Only with the PP running off battery does the sound really become totally independent of the AC (of course).

Mani.

Hey Nick, yep they did.

I think you're absolutely right to be concerned about the safety of these devices in a domestic setting. I may well bypass them unti there is a common consensus on how they can be used safely.

But I will definitely spend a day or so trying different direct/isolation-trannie/balanced-trannie/regenerator configurations and report back what I find. It could be that simply sticking with the house mains/PE is the best way to go. (But I doubt it...)

Mani.

Hey Paul, thanks for sharing. I'll come back to you once I've had a chance to digest all your points.


Yeah I know. For the last 6 months or so I've been using a pair of 5KVA balanced trannies (one for my main system, one for my study/office system) after my 15KVA isolation trannie. I haven't played around with various configurations yet (just no time), but may well bypass the isolation transformer altogether if it's not helping. Furthermore, I now have a PurePower 2000 regenerator in the mix after the balanced trannie for my study/office system. I've just today ordered a new PurePower+3000 regenerator for my main system. These things do something wonderful to the sound, provided everything is plugged into them (including the PC). I'm not sure if it possible to achieve what they do in any other (cheaper) way, but if there is, I've not found it.

Back with more thoughts later.

Mani

I just wanted to resurrect this thread because it's so important and of so much relevance to other topics.

I'm no electrical engineer, and was pretty bad at electronics at school and uni. But here are my thoughts on what's going on with your AC mains. Please feel free to comment on any of the points below:

1. The Neutral of your AC mains is bonded to your house's PE.

2. In an ideal situation, the Neutral and the PE should sit at the same potential.

3. A dedicated PE can never truly be isolated from the house's PE. There will always be some finite resistance between them (MegaOhms) and therefore a potential difference.

4. It's a really, really bad idea to have some components (that are themselves connected together via interconnects, USB cables, etc) using the house's PE and others using a dedicated PE.

5. A dedicated PE on its own is pointless. You just ensure that you invalidate point 2.

6. The only way that a dedicated PE makes sense is to use an isolation transformer that allows you to bond the dedicated PE to the Neutral of the secondary.

Thoughts?

Mani.

Hi Paul, we all know that grounding and PE are a nightmare story. My understanding is that my amps are configured in exactly the same way as yours are and the NOS1 too, i.e. signal ground is not connected to PE. But as you say, who knows what happens in other components or the PC?


Generally I would characterize grounding issues as increasing the brightness, glare and edginess of the sound. It can sound more detailed at first, but with prolonged listening you realise that this is superficial detail that becomes fatiguing with time.

Does your 'dramatic improvement' match this?

Mani.

Hi Coen, thanks for the explanation. Really appreciated, and I think I get it. So apart from a varying output impedance, this seems like a pretty neat little 'trick'.

I would have used these passives in the upper 1/3 of their range (from -18dB to -6dB) and maybe here the output impedance of the passives and the input impedance of the poweramp played a part in the difference in sound I was hearing. I can't even remember which poweramp I originally used but whichever it was, maybe its input impedance was lower than ideal for the passives. But I do know that all interconnects were 1m or less in length.

In any event, the digital volume control in XX sounded the best... for whatever reason.

Mani.

Well, I always was terrible at electronics. So could someone explain how a single 'pinch' resistor could be used for both phases?

Mani.