Wire and voltage/current requirements

[AtomicMassUnit]

What do you guys use for wire in the power supply? The reason I ask is my local electronics shop has wire rated for 300 volts max, so I'm assuming this wouldnt work in my tube amps with 400+ volts. What were the ratings on the old Fender and Marshalls?

[Tom Phillips]

Atomic,
I use 600V rated wire as my standard. Lower rated wire will "work" in most locations in an amp but I just stock the 600V stuff and don't worry about it. Cost difference is not a factor for what I do and I like the thicker insulation for most uses.
Regards,
Tom

[markbul]

The rating is not for the voltage carried by the wire, it's for the voltage difference between inside the insulation and outside. So if you have a wire at 350V in the air between an eyelet and a tube socket lug, it's not exceeding a 300V rating. If the same wire at 350V is laying directly against the chassis - at ground potential of 0V - then it is exceeding a 300V rating.

I'm sure there's a big safety cushion in the rating - plenty of people build amps with 300V wire. I still have some 300V I'm using, but my last buy was 600V just to be safe. I think I got it from McMaster-Carr.

I think the cloth insulation wire in vintage amps is 300V - the 600V cloth stuff for sale I've seen has extra PVC under the cloth.

[AtomicMassUnit]

That makes me feel a little better. I built an amp using 300 volt wire and another tech was going around saying it was a death trap basically, waiting to electrocute anyone who played it, although I never had a problem. Anyway, I rebuilt it with 600 volt wire to be safe, and ordered a bunch so it won't be an issue later on.

[Amp Kat]

Wire also has a VA rating. It's not how much voltage but how much current X the voltage = power. The AC input wires can be quite small actually but after the primaries of the transformer and the secondaries is where the power starts. Note the large wire for the heaters even though it's only 6.3 volts it's carring up to almost 7 amps in cases. Even tough the b+ is 400 to 500 volts it is only carrying around 100 ma's. The grounds should be a good thick wire around 12 to 14 AG for good contact. The thickness of the wire at certain places would bother me more than the voltage rating.

[Mark Lavelle]

As I understand it, there are two different but equally important issues:

1. Exceeding the voltage rating means a risk of arcing through the insulation.
2. Exceeding the current rating means a risk of melting the wire and/or the insulation.

Either way you risk something shorting out...

FWIW, I don't recall ever seeing a VA rating for plain wire.

[AtomicMassUnit]

Can any of you recommend some really good stranded wire that takes solder well and will stay put when you bend it?

[kg]

Wire also has a VA rating. It's not how much voltage but how much current X the voltage = power. The AC input wires can be quite small actually but after the primaries of the transformer and the secondaries is where the power starts. Note the large wire for the heaters even though it's only 6.3 volts it's carring up to almost 7 amps in cases. Even tough the b+ is 400 to 500 volts it is only carrying around 100 ma's. The grounds should be a good thick wire around 12 to 14 AG for good contact. The thickness of the wire at certain places would bother me more than the voltage rating.

sorry, but wire does NOT have a VA rating.

as mark points out, the conductive metal carries a CURRENT and really could care less about what voltage is impressed upon it.

the insulative jacket protects against creating a conductive path between the conductor and anything else around. it has a VOLTAGE rating which is proportional to its dielectric properties and its thickness, and really could care less about what current the internal conductor is carrying (well, right up to the point where it melts, at least).