d) at least one connector must safely take 360Vdc (equals 250v AC
rating).

Morning Andy.
That's odd. Most connectors and relays have a much *lower*
rating at DC than AC.

I was just doing a standard calculation as for capacitors - usually
about 1.4 to 1. Why is it different with connectors?

I picked a nickel plated NATO style connector These are available
in 9,12,16,21,26 way. The working voltage decreases as the density of
pins increases. RS part number for the 9 pin male plug is 234-685.
They cost about Euro 17. The matching female connector for the PSU end,
and also the cable connectors are
about the same price. So a complete set, of chassis and cable
connectors
comes out at about Euro 70. Both the Hirschman and the Amphenol NATO
connectors are much cheaper at about Euro 8 for the 8 pin. They are
either grey or olive drab. That is not a lot of money for such a good
connector. (Euro 32 for a
set)

I'll look again at Amphenol and the above - they looked expensive in
the Farnell catalogue. 70 euros is quite a lot, 32 is better. The
Speakon 8 way comes in cheaper and is more available, plus Dave made
the excellent point it's shrouded and so no danger on the amplifier end
from B+ caps. Doesn't matter with a preamp, but worth considering with
a three stage amp where to put the smoothing.

I have an uneasy feeling that the D connector female is not
sufficiently touch-proof for safe use above 70VDC.

It wouldn't have to be - it would only need to supply low voltage low
current filaments. The bigger plug would do the B+. Both connections
would have to be earthed. And, as Iain says the one with the B+ would
have to be screened.

Firstly you have to find a connector that is rated for the
DC voltage you need, *in a domestic environment* Some broadcast
and studio connectors, are rated at 1500V industrial but only 70V
domestic.
For your private use, you have a greater freedom of choice, and are
only dependent upon what an insurance company will accept. But if
you plan to sell to the general public then the situation is different.


Bill Beard used 8 pin Speakons for umbilicals. These are presumably
rated 250v for domestic as well as industrial. That's going back a few
years. Neutrik has downgraded all its 250v rating for XLRs to 50v in
latest literature - presumably this is domestic? Same plugs of course -
data sheet still says 250v and their salesman confirms it. I'd be
looking at up to 350v, so may be on dodgy ground here. No free lunches.
I'm OK with the filaments in the D connectors, but still need to look
at the B+ situation. Length of lead is interesting - never thought of
that. Loads of new regs coming in it seems.

"Andy Evans" wrote in message
oups.com...
d) at least one connector must safely take 360Vdc (equals 250v AC
rating).

Morning Andy.
That's odd. Most connectors and relays have a much *lower*
rating at DC than AC.

I was just doing a standard calculation as for capacitors - usually
about 1.4 to 1. Why is it different with connectors?

Odd isn't it. perpelexing too is that the same connector has different
ratings for different uses (military, broadcast or domestic)

I'll look again at Amphenol and the above - they looked expensive in
the Farnell catalogue. 70 euros is quite a lot, 32 is better. The
Speakon 8 way comes in cheaper and is more available, plus Dave made
the excellent point it's shrouded and so no danger on the amplifier end
from B+ caps.

That still may not be enough. You may well find that you are required
to have no DC at all on the chassis connector pins when the cable
connector is removed.

Power amps with separate psu are quite unusual these days. I have a
feeling that the safety regs might well be the reason. Solutions that were
common place in the 60s and 70s, like for instance the octal connector
between psu, amp and preamp, are now strictly forbidden, as are fixed
mains cables, and any other mains connector except the IEC type (with
the possible exception of the Speakon, I am not sure)

You have to be very wary. If your neighbour's world champion, best of
breed Rottweiler bites through your DC cable, it could cost you a pile
of the elusive spondoolicks.

Iain

"Andy Evans" wrote in message
oups.com...

Bill Beard used 8 pin Speakons for umbilicals. These are presumably
rated 250v for domestic as well as industrial.

The Speakon 8 way type NL8MPR is indeed rated at 250VAC.
However, it may *not* be used as a a mains connector.
Presuming it was OK for 250VDC would that he enough for you?

That's going back a few
years. Neutrik has downgraded all its 250v rating for XLRs to 50v in
latest literature - presumably this is domestic?´

Many companies have done the same. The old round Bulgin connector
used widely as a mains on prof audio equipment is now rated at only 50V.
However, it may be used at higher voltage as an interconnect within the
chassis (industrial)


Same plugs of course -
data sheet still says 250v and their salesman confirms it. I'd be
looking at up to 350v, so may be on dodgy ground here.

The connector I quoted you is OK to 7.5A at 380V IIRC.

No free lunches.

Indeed no. You need to get a copy of the manufacturer's CE
declaration to be on really safe ground.

I'm OK with the filaments in the D connectors, but still need to look
at the B+ situation. Length of lead is interesting - never thought of
that. Loads of new regs coming in it seems.

These are mainly covered in the CE markings directives. But it is
very complex indeed. They refer to low voltage as 1500V !!

Iain

That still may not be enough. You may well find that you are required

to have no DC at all on the chassis connector pins when the cable
connector is removed.

that would indicate all smoothing in the PSU box. Can be done.

Power amps with separate psu are quite unusual these days. I have a
feeling that the safety regs might well be the reason. Solutions that
were
common place in the 60s and 70s, like for instance the octal connector
between psu, amp and preamp, are now strictly forbidden, as are fixed
mains cables, and any other mains connector except the IEC type (with
the possible exception of the Speakon, I am not sure) You have to be
very wary. If your neighbour's world champion, best of breed
Rottweiler bites through your DC cable, it could cost you a pile of the
elusive spondoolicks.

Two monobloks is looking like the easy solution. I have all the
amplification and PSU stages on seperate top plates, so can plug them
into any chassis - stereo, mono. whatever. I was thinking of a seperate
PSU for development purposes, to try out different valve circuits, but
I can do that in-house and then just construct the final units as
monobloks. Not sure what to do about the preamp - that's an easier
situation as you found.

http://www.rapidonline.com/productin...moduleno=72443

How about these? Rated 415v

"Andy Evans" wrote in message
ups.com...

That still may not be enough. You may well find that you are required
to have no DC at all on the chassis connector pins when the cable
connector is removed.

that would indicate all smoothing in the PSU box. Can be done.

Well, I thought it better to decouple at the amp end of the
umbilical with a pair of 220µF electolytics, and so used a relay there also.

Power amps with separate psu are quite unusual these days. I have a
feeling that the safety regs might well be the reason. Solutions that
were
common place in the 60s and 70s, like for instance the octal connector
between psu, amp and preamp, are now strictly forbidden, as are fixed
mains cables, and any other mains connector except the IEC type (with
the possible exception of the Speakon, I am not sure) You have to be
very wary. If your neighbour's world champion, best of breed
Rottweiler bites through your DC cable, it could cost you a pile of the
elusive spondoolicks.

Two monobloks is looking like the easy solution. I have all the
amplification and PSU stages on seperate top plates, so can plug them
into any chassis - stereo, mono. whatever.

Now that sounds like an excellent "modular" idea, Andy.

I was thinking of a seperate
PSU for development purposes, to try out different valve circuits,

That's what I do. I have a Solartron regulated bench PSU 600V at
0.5A plus heaters and a bias tap. I also have a separate Farnell reg
supply 10A at 10V for heaters, plus another 100V at 100mA which I invert
as a bias supply. With clean DC you know that your development modules
are as good as they can be.

but
I can do that in-house and then just construct the final units as
monobloks. Not sure what to do about the preamp - that's an easier
situation as you found.

Yes indeed. When you get down to 265VDC things are not quite so
problematic. But you will still need the safety relay.

regards
Iain

"Andy Evans" wrote in message
ups.com...
http://www.rapidonline.com/productin...moduleno=72443

How about these? Rated 415v


:-.))))

Three phase mains connectors?

Iain Churches wrote:
"Andy Evans" wrote in message
ups.com...
http://www.rapidonline.com/productin...moduleno=72443

How about these? Rated 415v


:-.))))

Three phase mains connectors?

http://www.waltherelectric.com/produ...e/overview.cfm

these are splashproof connectors, but unfortunately are huge, like
100mm by 50mm

In article .com,
Andy Evans wrote:
That's going back a few years. Neutrik has downgraded all its 250v
rating for XLRs to 50v in latest literature - presumably this is
domestic?

Yes - a latching mains connector doesn't conform to UK regs for domestic
use. The LNE disappeared some years ago because of this, IIRC. There are
also regulations on some outlets being shuttered. So all in all Neutrik
probably just decided to restrict the recommended applications to extra
low voltage.

--
*I speak fluent patriarchy but it's not my mother tongue

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