External PSU connector for 250V and 48V

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bruce0

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Joined
Jan 24, 2010
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I have a safety question.

I want to keep the B+ PSU outside the case of a preamp I am building, so I found a PSU case that will sit on the floor and hold my 250V and 48V supply's.  I plan on using the 48V for Phantom, and for tube heaters in series.

I realize the tube heater current is significant, so my cable will need to be substantial.

What I am concerned about is the connectors.

Can I use a 5 pin XLR connector (female of course) for the PSU or must I use some other connector?

Is there enough separation in a 5 Pin XLR for 250V?
Will 1 pin handle the heater current for 4 tubes (4 12V heaters in series)?

I plan on a pin out of:

1- Chassis
2- Ground
3- No Connection
4- +48V DC
5- +250V DC

Chassis and Ground will be joined in the PSU.

Pins 2 and 4 will have heavy conductors for the heater current.
Cable will be relatively short (3 feet maybe a little longer).

I plan on using Power One open frame PSU's fused in an IEC connector to mains power, and putting a fast blow 50mA fuse on the 250V DC circuit (4 tubes will probably consume 50mA of B+ or less) for safety.  I will also fuse the 48V, but I imagine that will be a pretty high current fuse ( 300mA or so for 4 tubes in series approx. )

Is this a whacko idea? 
What connector should I use instead of 5 pin XLR?

I don't want the PSU in the Preamp Case.
I plan on the PSU being able to supply 3 such preamps (3 separate 5 pin female xlr jacks)

Any advice would be appreciated.

(The current requirement seems reasonable as most of us with API racks are doing more current than that on the bipolar rails using 5 pin xlr, but I am worried about isolation of the 250V and any other safety suggestions).
 
bruce0 said:
(The current requirement seems reasonable as most of us with API racks are doing more current than that on the bipolar rails using 5 pin xlr, but I am worried about isolation of the 250V and any other safety suggestions).

That's right... current won't be a problem.

About isolation, Gyraf uses 160V on a 7 pin XLR. In air you have 60KV to make 1cm arc, so wouldn't be a problem if soldered right, using heat shrink should be safe.

JS
 
BUT if you have any kind of reservoir capacitor behind the XLR-M, you can still burn your fingers by touching it after connector is removed.

Some manufacturers uses a relay that only opens to the HV circuit while another voltage (in this case 48V) is present on the xlr.

Jakob E.
 
bah... 500V only tickles.

I can't imagine the HV would stay above 40V for more than a couple seconds in a typical preamp? If this were a commercial product, I'd agree with Jakob in that you need an extra layer of idiot proofing... but I know you're smarter than the average bear, so I wouldn't bother.
 
Hello,

dielectrical strength on a e.g. Neutrik NC5FD-L-1 is 1,5 kvdc after their specs.

Hope to have helped (and hope to have the german word "Durchschlagsfestigkeit" translated correct),

Udo.
 
Udo - thanks - I looked but couldn't find the spec, yes dielectric or dielectrical are good translations.
Jacob - excellent point.  One preamp is a modified G9, and it does have reservoir caps on the HT (although they would drain fast if the tube was hot a burned out filament could have a big surprise in store (since all 4 tubes would go out) so the relay sounds like a good safety tip, or maybe just a low value drain resistor (I can have a pretty big PSU externally ).
Rodney and JS thanks

You guys are great - this makes me feel more comfortable -.... Long silence.... Zaaap!
 
[silent:arts] said:
You could use speakON if you want to go extra safety and touch proof:

http://www.neutrik.us/en-us/speakon/fc-series/nl8fc

I like the XLR, I don't use 5pin except for power, and I do the power connections myself.  If I had speakon... some bozo would fry the voice coil with 48 volts. or 250.  I mark the power ports and cords yellow on both ends.
 
I think a 5 pin XLR is marginal at 250V dc. The connector is rated at 50V ac which, liberally interpreted, could be as much as 150V dc but definitely not 250V.

Although rather bigger, I would recommend using Speakon connectors.

Cheers

Ian
 
ruffrecords said:
I think a 5 pin XLR is marginal at 250V dc. The connector is rated at 50V ac which, liberally interpreted, could be as much as 150V dc but definitely not 250V.

Although rather bigger, I would recommend using Speakon connectors.

Cheers

Ian
Ian is right,I must have overseen it,pardon!
Here's the link:

http://www.neutrik.de/de-de/xlr/dl-serie/nc5fd-l-1

You must click on "Technische Informationen-------anzeigen".

Best,

Udo.
 
kante1603 said:
Ian is right,I must have overseen it,pardon!
Here's the link:

http://www.neutrik.de/de-de/xlr/dl-serie/nc5fd-l-1

You must click on "Technische Informationen-------anzeigen".

Best,

Udo.

No problem. It is a pity really because Speakons are quite big and XLRs are quite neat. It would be nice if there was something in between the two that would do the job.

Cheers

Ian
 
ruffrecords said:
I think a 5 pin XLR is marginal at 250V dc. The connector is rated at 50V ac ....

Hi,
Canon rates XLRS to 133V AC.
I'm using 7pin Neutrik XLRs for tube mics (150-200V DC) without any problem.
Regards,
Milan
 
moamps said:
ruffrecords said:
I think a 5 pin XLR is marginal at 250V dc. The connector is rated at 50V ac ....

Hi,
Canon rates XLRS to 133V AC.
I'm using 7pin Neutrik XLRs for tube mics (150-200V DC) without any problem.
Regards,
Milan

Clearly you need to take care in choosing your manufacturer as Neutrik only rates theirs to 50VAC.

Cheers

Ian
 
These are what I use for all of my power supply connections in various sizes.  A little expensive, but you only have to but (I mean buy) them once.

http://www.mouser.com/Search/ProductDetail.aspx?R=MS3106F18-1Svirtualkey65400000virtualkey654-MS3106F18-1S

http://www.mouser.com/Search/ProductDetail.aspx?R=MS3102E18-1Pvirtualkey65400000virtualkey654-MS3102E18-1P

Best,
Bruno2000
 
bruno2000 said:
These are what I use for all of my power supply connections in various sizes.  A little expensive, but you only have to but them once.

http://www.mouser.com/Search/ProductDetail.aspx?R=MS3106F18-1Svirtualkey65400000virtualkey654-MS3106F18-1S

http://www.mouser.com/Search/ProductDetail.aspx?R=MS3102E18-1Pvirtualkey65400000virtualkey654-MS3102E18-1P

Best,
Bruno2000

Yes, Amphenol are the one and only when it comes to high reliability connectors. The free end is quite expensive but the chassis part is about the same as a Speakon.

I just did a very quick survey of 5 pin XLR specs at Farnell:

Deltron 250V ac
Amphenol 50V ac (consumer) or 133V ac (other)
Pro-signal 60V ac
Canon 133V ac
Neutrik 50V ac

I suspect there's something in the 'consumer' versus 'other' type of application - the Amphenol is the only one that mentions this. The Canon types do seem to be extraordinarily expensive.

Cheers

Ian
 
I see that you only want 4 wires attached in the first post here.
Maybe a Neutrik 4-pole Speakon like NL4xx-xx (a lot of types out there....).
Would fit in a D-Series size mounting hole......

Must search for specs first,bit who knows......
O.k.,found it,specs looking good (250vac,4kv dielectric strength),but later on it says:

Attention speakON is NOT to be used as an AC mains or power supply connector!
:'( :'( :'(
Don't know if that means psu use in general or just on the entrance/primaries side?

Best,

Udo.
 
Thanks for all the input! 

The amphenol connectors look great, but I was wondering if anyone has any experience with the mini-boss or device-net factory automation connectors and assemblies from Amphenol?

They have 3 4 and 5 pin versions.  I think I could use the 4 pin version. One nice thing about these is they have a "Tee" connector, that would let me cascade 2 or three amps in parallel without wiring them all back to the PSU.  Fewer cables, fewer connectors, 16AWG conductors, and they have preassembled cables.

They say they are for factory automation, rated for up to 600V dc.

Anyone used those?

Cables on demand have some, and mouser sells them too.  Cables on demand has good service, and prices seem better.

https://www.cablesondemand.com/ClearSV/True/category/180/URvars/Catalog/Library/InfoManage/FACTORY_AUTOMATION_CABLES.htm

Mouser carries it too.

http://www.mouser.com/catalog/catalogusd/646/2614.pdf
 
I've been using these at a lower voltage but they seem pretty robust - might be worth experimenting. They don't match up with any common audio connectors, and they're very cheap, is why I tried them.

sku_133101_3.jpg


http://dx.com/p/diy-16mm-5-pin-gx16-aviation-plug-socket-connector-silver-5-pieces-pack-133101
 
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