Wire gauge for replacement console PSU cable

[Potato Cakes]

Hello, everyone.

I need to make a replacement PSU cable that uses a 7 pin XLR, but I'm not quite sure which kind of wire to use. I looked at some of the tube mic PSU cable as a couple of conductors are larger and seem appropriate for the +/- rails. My hangup is the PSU fuses for the power rails are rated at 10amps,  and I don't know if the gauge of wire needed for proper heat dissipation for DC is the same for AC. The console is a TAC Scorpion 24x16 that is being fixed up with potentially higher draw chips. The distance of the PSU to the console will be about 30 feet. Any insight would be appreciated.

Thanks!

Paul

 

[PRR]

You want a wire-table.

Here's a fish for appetizer.

Will it melt? #16 will easily carry 10 Amps.

Will it sag? You don't say what voltage. Assuming 15V and wanting <1V sag you need <1V/10A = 0.1r. Your run is 30 feet. Wire tables commonly list Ohms per 1,000 feet. So look for 3.3 Ohms. This is #15, not a common size, use #14. #14 is 2.6r/1000', so 0.08r in 30', and 0.8V drop.

Will it melt? (part 2) #14, three wires in cable, is rated 20A with 140F wire. I suspect 4 of your 7 wires actually carry 10A current. This seems safe.

Will it sag? (part 2) 0.8V sag is not-large compared to 15V, but also not negligible. Do you care? Alternates are +/-24V in the cable with local on-board regulation to +/-15; or remote-sense supply which will force 15.8V if needed to get 15V at the far end. Obviously these techniques need more stuff. It may be that the system you have "assumed" the power supply would be "near" the console, and remoting it may get complicated.

 

[ruffrecords]

Two things concern me about what you plan:

1. A potential 10 amps through the pins of a 5 pin XLR connector which is only rated for 7.5A

2. PSU 30 feet from the console. This is bad news in so many ways. The common mode impedances are bad news for noise. crosstalk, stability. Thick cable may make the  dc resistance may be low but  the inductance will still be an issue.

Cheers

Ian

 

[Newmarket]

Worth bearing in mind that while it's reasonable enough to use the 10A Fuse Rating as a 'Design Value', the actual max current used is hopefully significantly less.
Ordinary fuses are fairly crude devices and their basic function is to protect against overheating and fire.
They won't blow quickly unless the current is significantly more than the rated current. The rated current is given for a specified temperature rise of the fuse element under stated conditions.
So if you have, say a 10A rated fuse carrying 10.5A it's unlikely to blow - at least not for a while - but there will be some temperature rise of the fuse and hence additional resistance in the power path.

 

[Potato Cakes]

Thanks for all the replies. I apologize for not stating the voltage. It's +/-17V and 48V. Also, I was mistaken, it is a 4 pin XLR not a 7 pin. 0V reference goes down the cable and is separated from ground by a 10R resistor. I don't actually need the 48V for my purposes as the console will be line input only. Maybe if I try some 14/3 stranded copper.

Thanks again for all the info. I have a better understanding of what I should be testing for when I get to that point in the restoring process.

Thanks!

Paul