John Curl's Blowtorch preamplifier part II

[scott wurcer]

Originally Posted by john curl

Interestingly enough, Hi Fi books from the '50's used to suggest the same thing. It was easier then, with just two leads, and no 3'rd wire ground, at the time.

Even at the risk of an occasional "hot" chassis.

[Steve Eddy]

Originally Posted by john curl

Finally, some common sense about ground leakage!

If you consider swapping hot and neutral at the AC mains outlet to be "common sense," you should get out of the business.

Interestingly enough, Hi Fi books from the '50's used to suggest the same thing. It was easier then, with just two leads, and no 3'rd wire ground, at the time.

And in the 50's, it was common to wire the equipment chassis to neutral. So yeah, now let's go and flip the plug around on one piece of equipment.

*sigh*

se

[simon7000]

Originally Posted by Steve Eddy

I don't know how you do things over in France, but over here, you should NEVER change the sense of the AC mains hot and neutral.

They should always be wired like this:



se

What he is talking about is the winding closest to the transformer core should be connected to the neutral. To conform to code this should be corrected inside the piece of gear.

Most transformers pay no attention to which primary wire is the winding start.

I do have a sample of a Chinese R core power transformer where the 120 Volt hot lead is color coded green!!!!

The other issue is the use of Belden 1023A cable. It is a shielded twisted pair with a foil shield. HOWEVER one conductor is copper the other is constantan! It is intended to attach to thermocouple and not introduce any voltage errors.

[magnoman]

I presume they are talking about swapping the primary transformer phase so that the secondary capacitively sees more of the neutral end.

Thanks
-Antonio

[simon7000]

Originally Posted by magnoman

I presume they are talking about swapping the primary transformer phase so that the secondary capacitively sees more of the neutral end.

Thanks
-Antonio

Actually I think it is the leakage to the core that is more of a concern.

[Steve Eddy]

Originally Posted by simon7000

What he is talking about is the winding closest to the transformer core should be connected to the neutral. To conform to code this should be corrected inside the piece of gear.

Yes, but he wasn't talking about doing it inside the piece of gear. He was talking about doing it at the AC outlet.

I do have a sample of a Chinese R core power transformer where the 120 Volt hot lead is color coded green!!!!

Not surprising. A Chinese amp and DAC maker (Audio g-d) was shipping his gear with power cords that had the hot and neutral reversed.

se

[magnoman]

Originally Posted by simon7000

Actually I think it is the leakage to the core that is more of a concern.

In general or does that change with primary phase?

Thanks
-Antonio

[john curl]

In the '50's and '60's, almost all hi fi and other appliance AC plugs were just 2 and NOT 3. AND they were NOT polarized.
I worked at UL Labs, about 50 years ago, for about 1 year as a test tech. Which way you plugged in the plug just was not a concern at the time. So many 'far fetched' conditions had to occur before any serious injury, that extreme measures did not seem to be important enough to consider. You could even suffer a mild 'shock' from a guitar amp, for example, and it was considered OK, so long as it could not be fatal. Of course 3 prong plugs existed in restaurant appliances and such, when exposure to water and water pipes was much more common.
Later, plugs became polarized, and then 3 prong plugs became more standard, especially with metal cased audio equipment.
The most dangerous appliance I have seen in today's world is a toaster.

[Esperado]

Originally Posted by jneutron

However, the twisted pair will share a common centroid by integration along the cable length.

That's what i was trying to explain. Same thing if the two wires are strait and the drain symmetrically situated all the way.
Belden take care of those details, as, by example, the way wires are shielded, for they don't change their geometry when the cable is creased.
One other thing, i don't know if it is the metals used, (Coper, Constantan), but the sound is very neutral and detailed comparing the whole box length with a short circuit.

About the grounding tip, i suppose we have some norm about hot and neutral, never respected. But norm is severe with earths diameter and impedance. my suggestion was not to modify wall outlet, but what you call "Power distribution units" ? Right ?

[marce]

Some more info to add to the fun, one article on shielding 2 on interference free systems (ie reducing EMC)
Tony Waldron's EMC ranting and ravings