Advice on a power supply umbilical needed.
 

"Don Pearce" wrote

You can use that one spare connection for ground, but is that
something different from the one you already nominate as Earth? Not
too clear about that.


Having two parallel paths for earth reduces the possibility of the chassis
becoming "live" in the event of failure of the earth path between the
chassis.

Phil says that an earth continuity conductor should not also be a current
carrying conductor. Easier said than done in a case like this. If HT- is
connected to mains earth at the PSU, as would normally be the case, then it
is impossible to force HT current to flow through a designated HT- lead and
not through a separate earth lead.

David.

Advice on a power supply umbilical needed.
 

"Andy Evans" wrote

David, note
that XLRs are now rated as 50v. They were rated at 300v or so but have
been re-rated in conformity with newer regulations,

See my point in another post about access to the uncoupled connector. Best
of luck finding a connector which *is* rated for 500V in domestic use!

David.

Advice on a power supply umbilical needed.
 

On Sun, 4 Oct 2009 10:41:49 +0100, "David Looser"
wrote:

"Don Pearce" wrote

You can use that one spare connection for ground, but is that
something different from the one you already nominate as Earth? Not
too clear about that.


Having two parallel paths for earth reduces the possibility of the chassis
becoming "live" in the event of failure of the earth path between the
chassis.


That protection is better if the other earth connection goes via
another route. Something like a bathroom bonding wire comes to mind.

d

Advice on a power supply umbilical needed.
 

"Don Pearce" wrote in message
...
On Sun, 4 Oct 2009 10:41:49 +0100, "David Looser"
wrote:

"Don Pearce" wrote

You can use that one spare connection for ground, but is that
something different from the one you already nominate as Earth? Not
too clear about that.


Having two parallel paths for earth reduces the possibility of the chassis
becoming "live" in the event of failure of the earth path between the
chassis.


That protection is better if the other earth connection goes via
another route. Something like a bathroom bonding wire comes to mind.


Don't get me started on earth bonding in bathrooms! Fortunately the rules
have changed in the new edition of the wiring regs, as the old bonding rule
made bathrooms more dangerous, not less.

However, to return to the topic. I think it unlikely that any valve amp with
two exposed chassis: one for the PSU and one for the amp, can ever be
entirely safe, especially if the interconnection is done with a plug and
socket. The best solution IMO is to enclose the two in a common enclosure.

David.

Advice on a power supply umbilical needed.
 

On Sun, 4 Oct 2009 11:03:40 +0100, "David Looser"
wrote:

"Don Pearce" wrote in message
...
On Sun, 4 Oct 2009 10:41:49 +0100, "David Looser"
wrote:

"Don Pearce" wrote

You can use that one spare connection for ground, but is that
something different from the one you already nominate as Earth? Not
too clear about that.


Having two parallel paths for earth reduces the possibility of the chassis
becoming "live" in the event of failure of the earth path between the
chassis.


That protection is better if the other earth connection goes via
another route. Something like a bathroom bonding wire comes to mind.


Don't get me started on earth bonding in bathrooms! Fortunately the rules
have changed in the new edition of the wiring regs, as the old bonding rule
made bathrooms more dangerous, not less.


Valve amp in zone zero, maybe? Provided you could run a valve off 12
volts, of course.

However, to return to the topic. I think it unlikely that any valve amp with
two exposed chassis: one for the PSU and one for the amp, can ever be
entirely safe, especially if the interconnection is done with a plug and
socket. The best solution IMO is to enclose the two in a common enclosure.


Amen to that.

d

Advice on a power supply umbilical needed.
 

"Andy Evans" wrote in message
...
I have some projects with 300b SET amps built on two chassis - power
supply and signal chassis. Right now I'm using amphenol 4 pin AP
series connectors for earth and HT - which is about 440v or 490vDC off
load.

I'm wondering about a simpler coax option, since I really only need HT
and earth (rest can be done with 4/5 pin XLRs and 4/8 pin speakons).
The umbilical can be fixed at the PSU end and detachable at the signal
chassis. So a female socket on the cable and a male one on the
chassis.

I have no experience of coax connectors - there's the cheap and
plentiful BNC, the more robust N type, then TNC, UHF etc etc. The
connector must be comfortable at 500v, but the other requirement would
be that the cable connector - presumably female - should be
sufficiently shrouded that it's very hard to touch since there's over
400vDC on it!!

Best choice here?


I have a valve phono stage with separate PSU and detachable 'Cliffcon'
umbilicals:

http://www.cliffuk.co.uk/products/cliffcon/index.htm

They are have a 'bayonet type' locking ring on the connectors and work very
nicely, but they aren't rated for 500V though. Contact them and ask for
their suggestions/recommendations - I'm sure you won't be the first to have
done so.

Advice on a power supply umbilical needed.
 

In article ,
David Looser wrote:
Don't get me started on earth bonding in bathrooms! Fortunately the
rules have changed in the new edition of the wiring regs, as the old
bonding rule made bathrooms more dangerous, not less.

Think you've misunderstood the reasons. It's *not* earth bonding, but
equipotential bonding. Ie, all the metalwork must be at the same potential.

--
*I'm pretty sure that sex is better than logic, but I can't prove it.

Dave Plowman London SW
To e-mail, change noise into sound.

Advice on a power supply umbilical needed.
 

"Dave Plowman (News)" wrote in message
...
In article ,
David Looser wrote:
Don't get me started on earth bonding in bathrooms! Fortunately the
rules have changed in the new edition of the wiring regs, as the old
bonding rule made bathrooms more dangerous, not less.

Think you've misunderstood the reasons. It's *not* earth bonding, but
equipotential bonding. Ie, all the metalwork must be at the same
potential.


And if that potential is 240V above the earthed floor?

The fact that the regs have changed in line with my suggestions suggests to
me that the wiring regs committee accepted my arguments.

David.

Advice on a power supply umbilical needed.
 

"Dave Plowman (News)" wrote in message
...
In article ,
David Looser wrote:
Don't get me started on earth bonding in bathrooms! Fortunately the
rules have changed in the new edition of the wiring regs, as the old
bonding rule made bathrooms more dangerous, not less.

Think you've misunderstood the reasons. It's *not* earth bonding, but
equipotential bonding. Ie, all the metalwork must be at the same
potential.


Actually it's the fact that it's equipotential bonding that makes it so
dangerous. True (and guarenteed) earth bonding would be fine.

David.

Advice on a power supply umbilical needed.
 

"Andy Evans" wrote in
message

I have some projects with 300b SET amps built on two
chassis - power supply and signal chassis. Right now I'm
using amphenol 4 pin AP series connectors for earth and
HT - which is about 440v or 490vDC off load.

I'm wondering about a simpler coax option, since I really
only need HT and earth (rest can be done with 4/5 pin
XLRs and 4/8 pin speakons). The umbilical can be fixed at
the PSU end and detachable at the signal chassis. So a
female socket on the cable and a male one on the chassis.

I have no experience of coax connectors - there's the
cheap and plentiful BNC, the more robust N type, then
TNC, UHF etc etc. The connector must be comfortable at
500v, but the other requirement would be that the cable
connector - presumably female - should be sufficiently
shrouded that it's very hard to touch since there's over
400vDC on it!!

Best choice here?

http://www.ittcannon.com/uploadedFil...0VoltageDS.pdf

A bit over the top, and probably way too salty for you.