Umbilical cord construction

[jcareysr]

I am thinking about a separate power supply for my Tubelab SE and need some advice about how to make the umbilical cord. I have about three feet in mind.
Need advice about wire size, connectors, etc.
thanks for any help

 

[Cold Macaroni]

I can't offer much insight, but I recently spent a lot of time in the understanding star grounding thread, and I think I recall a few pages that were dedicated to connector type and selection and grounding schemes for umbilical cords and external power supplies.

 

[jcareysr]

Umbilical

Thanks for referring me to the grounding thread. Lots of helpful information there.

 

[Evenharmonics]

Try these plugs. http://www.mouser.com/Catalog/catalogusd/645/1499.pdf
http://www.mouser.com/catalog/catalogusd/645/1525.pdf

 

[jcareysr]

Umbilical

Thanks Evenharmonics--that's very helpful. Lots of choices and adequate current and voltage ratings.

 

[boywonder]

How much power supply will be located remote from the amp?

I used Tubelab's PCB and only had the power transformer remote since the board makes it convenient to hang on to the caps.

I used a 9 pin Amp circular plastic connector to mount the power tranny on a separate enclosure, and I ended up needing all 9 pins to do it. I had some hum and needed to run a separate ground for the CT, and fortunately I had one extra conductor to do it. I originally had the transformer CT grounded in the PS chassis, all the grounds in the amp chassis tied together and one conductor tying the two chassis together. I ended up with the CT on one umbilical conductor and the chassis grounds on another.

The gory details are here:

http://www.diyaudio.com/forums/tubelab/184051-reducing-filament-hum-tubelab-se.html

I had a piece of Belden 9 conductor cable, but you can easily use separate wires in braided sleeving, just make sure the wire insulation voltage rating is adequate (600V rated wire for B+ conductors)

The Amp circular plastic connectors (CPC series) are affordable and are available in several shell sizes, sexes, pin counts and tin plate or gold plated pins. Also make sure your live power supply side connector is sockets to avoid the potential of having live voltage on pins when the connector is disconnected (assuming you want a connector). The pins for these require a crimper.

 

[jcareysr]

Umbilical

Thanks Boywonder. There's a lot to consider when using an umbilical setup--putting everything on one chassis is becoming more attractive.

 

[qusp]

if youve got the budget and a fetish for milspec connectors you really cant go past the ITT cannons

 

[boywonder]

if youve got the budget and a fetish for milspec connectors you really cant go past the ITT cannons

.....or Amphenol metal shell connectors........these were leftovers from a medical device prototype built about 10 years ago....

 

[qusp]

yep, i picked up a box of the above for a song from the FS section here @ 100EU for 10 x cable mount and 7 x panel mount, gotta be happy with that. they still make that model, nearly 140ea and ~50ea respectively at Farnell =) I like the amphenol too, but not as much as the Cannons. the Amphenol are more readily available than the ITT as the ITT have export restrictions.

I use the Amphenol hybrid Dsub mixed signal umbilical connectors too, very nice.

 

[jcareysr]

Umbilical

Thanks but my fetish and budget are more in the five to ten dollar range.

 

[qusp]

then your options are very limited

 

[Nikon1975]

The cable I did for the Tubelab SE was using two coaxials for the HV DC and two twisted wire for the AC. I would add an additional conductor for the earth.

I used a connector only on the PSU side. You can look for the "Cinderella castle" tube lab in the pictures.

D.

 

[boywonder]

Thanks but my fetish and budget are more in the five to ten dollar range.

The circular plastic ones (CPC connectors) should make the budget; you'll need a crimper, though (beg/borrow/buy). Strain relief on one end, connector on the other.

 

[jcareysr]

Umbilical

Thank you all for the very helpful ideas. It looks like there are lots of choices. One of the things I am unsure about has to do with the voltage ratings of the connectors--sometimes this is stated in the description and sometimes not. If I were to use an umbilical carrying b+ of about 400vdc I would want to use wire rated for that voltage, right? But do I need to be concerned about the sort of connector I would use or are they all capable of safely carrying that?

 

[Nikon1975]

To be picky, at startup your voltages are higher.

D.

 

[boywonder]

Thank you all for the very helpful ideas. It looks like there are lots of choices. One of the things I am unsure about has to do with the voltage ratings of the connectors--sometimes this is stated in the description and sometimes not. If I were to use an umbilical carrying b+ of about 400vdc I would want to use wire rated for that voltage, right? But do I need to be concerned about the sort of connector I would use or are they all capable of safely carrying that?

You do need to be concerned about the connector voltage rating, and you may end up exceeding the specs a bit since connectors rated for greater than 250V or so can be difficult to find. Keeping in mind that there is some margin built in for creepage clearance, folks here have exceeded the voltage rating successfully but YMMV. You won't be getting UL or CSA approval on your amp so you can stretch the specs a bit at your own discretion if you want to (you may not want to, though-completely up to you).

There are several tricks you can play also to increase the creepage clearing between pins such as using a connector with a greater pin count than you need and leaving out the pins around the B+ conductor, etc. if the connector has removable pins. Note also that many connectors rated for 250V working voltage have AC breakdown voltages exceeding 2KV; this will give you some idea of the safety margin. I just quickly scanned Digi-key, and there are some circular plastic connectors rated for 600V (some flavors of the Bulgin Buccaneer line, perhaps others).

My amp has been happily running 360V B+ through a 9 pin CPC connector for a couple of years now.

As far as wire goes, it's typically going to be either 300V or 600V rated. I would use 600V for the B+ and either rating for the other conductors, depending on what you have or what you can source. 300V rated wire for the other conductors may be the way to go if you want to keep the umbilical flexible.

As Nikon mentioned, your max B+ will be at startup and can be as high as 1.41 times your power transformer secondary voltage.

 

[qusp]

good tip boywonder, didnt think to mention the connector one end trick, even though ive used it myself on occasion. there are indeed good voltage margins on a lot of this stuff and ways to extend it further. current rating is more important than voltage here i believe

 

[buzzforb]

Easy and high quality option is speakon or powercon connectors. Have built safety of no exposed contacts and also allws for larger cables. I am using dh labs ac cable.

 

[boywonder]

depends on which conductor.....

current rating is more important than voltage here i believe

The B+ current is a mouse-fart (100-150ma or so), B+ voltage is 350-450V or so

Filaments are 5V and a couple of amps......