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Old 8th March 2008, 08:23 PM   #1
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Default Separate power supply - Umblical Cord


I am building a separate power supply for my 2a3 SET amplifier.
What is the best connectors and wire (gauge, stranded/solid?) to build the umbilical power cords?

I am thinking of:

a) XLR 4 pin for the bias voltages (300v, 280v). 23 Gauge solid silver cable
c) XLR 7 pin for the heater supply (2 pin each for the 2x 2a3 Heaters and 2 pins for the driver heater). 18 Gauge stranded copper.

Should I add a copper shield then a PVC insulation over the power cord?

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Old 8th March 2008, 11:53 PM   #2
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Don't use solid wire for cables that need to flex and silver wire in this application sounds like a waste. The connectors sound like they will work fine but I'm sure someone will get upset about the voltage being too high.
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Old 8th March 2008, 11:58 PM   #3
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Agreed, go for the superior mechanical capabilities. Make sure the connectors are rated for voltage/amperage. Stranded wire with more/finer strands is more durable when flexed, but the biggest practical difference will probably be the quality of the insulation (where good insulation is flexible, durable and long-lived).

Silver offers you nothing over copper here. Unless you think it's pretty for some reason and have the money to waste^H^H^H^H^Hspend ;-)

Copper shield on the umbilical gets you absolutely nothing.
"My name's Monty, and I break things."
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Old 9th March 2008, 01:22 AM   #4
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These plugs may do the job.
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Old 9th March 2008, 01:24 AM   #5
mach1 is offline mach1  Australia
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Do a search - the topic has already been covered extensively on this forum.
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Old 9th March 2008, 01:45 AM   #6
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Ya, use stranded copper with proper plugs. Silver power cables are pointless, silver signal cables are IMO also pointless but thats debatable.
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Old 9th March 2008, 03:24 AM   #7
TheMG is offline TheMG  Canada
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I don't really see many applications where silver cable would be any benefit at all especially when you consider the added cost. I mean, we're talking about tiny differences in resistivity.


Silver: 1.5910−8 Ω-m
Copper: 1.7210−8 Ω-m
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Old 9th March 2008, 06:25 AM   #8
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Thanks for all the help. The Cinch plug and socket sounds like the way to go. I will also stick to stranded copper with flexible insulation. It is interesting to learn that the copper shield is not helpful here.

Do we need to twist the copper wires? The heater voltages and biases are all D.C.
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Old 9th March 2008, 03:12 PM   #9
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Twisting the wires can't hurt. It may help with crosstalk being that the filaments are part of the signal chain. I'm surprised that cinch connectors are still being made, they have been around forever.
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Old 9th March 2008, 04:13 PM   #10
pftrvlr is offline pftrvlr  United States
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I ended up with 8 pole speakon NL8MP/NL8FC connectors. They are sturdy and reasonably priced in EBay. This cable is heavy gaugue and good fit for the connector:
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