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Old 16th September 2005, 11:16 PM   #1
alex278 is offline alex278  Netherlands
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Default Wire size for projects?

I'm halfway building my first amp, and halfway, I'm suddenly wondering how thick the wires in a typical tube-amp should be. Before, I've mostly done low-voltage stuff (TTL boards and so on), so I'm used to using 0.25 mm wire.

Of course, I know that for heaters you probably should use 1.0 mm wire or so, but how thick should the wire be in other places? Is 0.25 mm enough, or should I use thicker wire in selected places?
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Old 17th September 2005, 12:27 AM   #2
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If you can handle that tiny stuff, it's fine. I use 22 gauge (maybe 0.5 mm) for everything but filaments, easier for me to strip and solder.
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Old 17th September 2005, 03:31 PM   #3
mr mojo is offline mr mojo  United States
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Hey Alex,

Take a look here:

http://www.powerstream.com/Wire_Size.htm

I just completed my first amp as well:

First DIY amp pics-as promised!

I used 20ga for signal and 18ga for ground and filament.

Best,
mr mojo
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Old 18th September 2005, 09:04 PM   #4
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Default voltage rating for wire

I'd also like to know what other people use for voltage rating on their wire?
I've used 200v insulation on all my guitar amps, but I do have 600v wire available.
Is 200v insulation generally acceptable for a 400v B+?
Glenn
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Old 19th September 2005, 12:26 AM   #5
anatech is offline anatech  Canada
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Hi Glenn,
The voltage rating is the breakdown rating. Therefore, wire rated for 200V service is not safe for 400V service. There is a saftey factor but you wouldn't run a 200V cap at 400V - would you?

So ..... how do you feel about rewiring all those amps? You didn't sell them did you?

-Chris
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Old 19th September 2005, 01:06 AM   #6
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I use 30g wire wrap wire unless i'm lazy in which case i use strands of solid core Cat 5 (24g way easier to work with). Heaters need fatter wire.

dave
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Old 19th September 2005, 01:40 AM   #7
anatech is offline anatech  Canada
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Hi Dave,
I use CAT-5 all the time, for networking and telephone systems. At best the insulation will be 300 VDC. I have my doubts on that rating even.

I have no idea on the rating of your 30GA. Depends on the insulation. I bet it's around 100~150VDC since the wire can not support thicker insulation. Or it's exotic wire and okay for B+.

Quote:
Yeah "Too" all components including wire insulation have a maximum allowable voltage and indeed resitors.
Post #7 here

-Chris
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Old 19th September 2005, 01:55 AM   #8
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Quote:
Originally posted by anatech
I use CAT-5 all the time, for networking... 300 VDC.
That's about the limit of any amps i've done so far. I'm still a rookie so am working my way up with the voltages.

Quote:
I have no idea on the rating of your 30GA. Depends on the insulation. I bet it's around 100~150VDC since the wire can not support thicker insulation. Or it's exotic wire and okay for B+.
Two of my early tube gurus recomended it. I try to mostly use component leads for wiring.

dave
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Old 19th September 2005, 06:21 AM   #9
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When point-to-point wiring, you tend not to let wires cross, rub and lean about, so insulation is pretty moot anyway, I could wire with 20AWG bare if I felt like it

It's not much of a safety issue because if your hand somehow finds its way shoved below a live +400V tube chassis...shocking things are going to happen anyway.

Not recommended, but wire insulation is also overrated. Heck, I had like 5kV threatening the outside of a 24ga. 300V PVC insulated wire the other day, and it didn't say uncle!?

Oh, and also note that insulation isn't going to spontaneously break down and spark. The air around the wire, your primary defense, is much wider (between wires) and has a lower dielectric constant, so by and large, most of the electric field is across the air, not the insulation.

If you have to run hot lines along the chassis or twisted to low voltage wires, appropriate (600V+) insulation would be a good idea.

Tim
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Old 19th September 2005, 12:11 PM   #10
anatech is offline anatech  Canada
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Hi Tim,
At least if the wire is bare, you expect to have to keep it away from other things. It's just that beginners should be aware of the dangers and why things "just blow up".

I am comfortable with bare wire also, and cracked insulation. Still, the proper wire should be used. And yes, air makes a fine dielectric, but it's a crappy barrier. You and I know when it's okay to use bare or low voltage wire. I'll bet you were taught to use the correct stuff. The same should be pointed out to people just starting out. Otherwise, why do they make that expensive 600V (or better) wire anyway?

-Chris
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