Which Wire Where?

[Kregg]

Now that I have a few builds under my belt I'm curious about wire selection.
I noticed that power transformer, heater, and filament wires tend to be stranded wire and are the largest gauge in most amplifiers.
Also, the closer we get toward the preamp tubes the thinner the gauge.

What determines where solid or stranded wire is used?

[collinsamps]

You can use either as long as the current requirement of the circuit is met by the gauge selection. I can't stand trying to thread noval socket pins with any stranded wire and use solid for everything except shielded input / output wires. Transformers are 9 times out of 10 going to be 18ga stranded.

[Kregg]

Good enough, thanks!

[Bob-I]

I use 20AWG PTFE wire from Apex Jr for everything. If you tin it right it'll fit in the novel socket just fine and it doesn fracture as easily as solid. Of course I'm a clutz, if you're careful solid will hold up just as well.

[benoit]

I use 20AWG PTFE wire from Apex Jr for everything. If you tin it right it'll fit in the novel socket just fine and it doesn fracture as easily as solid. Of course I'm a clutz, if you're careful solid will hold up just as well.

+1 on the goods from apexjr.

[rmb550]

You should also confirm that the voltage rating of the insulation exceeds that of the circuit in question.

[Structo]

I use the stranded teflon stuff like Apex sells.

A little harder to strip but it is small diameter for the voltage rating.

18 ga on the heaters, fuse and power switches, 20 on everything else.

I had an issue with a broken solid wire once that drove me crazy trying to track it down.

[Bob Simpson]

You should also confirm that the voltage rating of the insulation exceeds that of the circuit in question.

Is 300V 18AWG stranded enough for power tube heaters?

Bob Simpson

[Kregg]

I picked up my wire here, http://www.bulkwire.com/
The stranded was rated 600v, the solid 300v.

[benoit]

You should also confirm that the voltage rating of the insulation exceeds that of the circuit in question.

Is 300V 18AWG stranded enough for power tube heaters?

Bob Simpson

That'll do fine.

[Phil_S]

Is 300V 18AWG stranded enough for power tube heaters?

Here's how the question gets answered. Add up the filament current. Your typical 3x 12AX7 required 0.3A ea. plus, lets say a pair of EL84 require 0.76A ea. That's 2.42A * 6.3V = ~15.3W. 300V is well above the 6.3V running on the heater circuit. This is why you really want something heavy enough, it's the watts and the wire is relatively cheap.

Go here for a chart on wire gauge and current limits.
http://www.powerstream.com/Wire_Size.htm
It says 18 ga is good for 16A. So, yes, you'll be good with 300V rated wire there.

I find stranded 18ga is much to much of a hassle to thread two pairs into a noval socket. I use 20ga solid for that. With octal sockets, it's not a problem and just about anything goes.

[Kregg]

Gotta love The Amp Garage. Thanks for the information you bring to the table gentlemen.

[Zippy]

Here's how the question gets answered. Add up the filament current. Your typical 3x 12AX7 required 0.3A ea. plus, lets say a pair of EL84 require 0.76A ea. That's 2.42A * 6.3V = ~15.3W. 300V is well above the 6.3V running on the heater circuit. This is why you really want something heavy enough, it's the watts and the wire is relatively cheap.

While it is true that voltage x current equals power, that is not how to determine the correct ratings for wire. Insulation is rated for breakdown voltage - pay attention to the voltage rating. Current handling capability is limited by conductivity and conductor cross section - pay attention to the wire's current rating (amps). You'll never see wire rated for power (watts).

It's not semantics.

[tonestack]

Is 300V 18AWG stranded enough for power tube heaters?

Here's how the question gets answered. Add up the filament current. Your typical 3x 12AX7 required 0.3A ea. plus, lets say a pair of EL84 require 0.76A ea. That's 2.42A * 6.3V = ~15.3W. 300V is well above the 6.3V running on the heater circuit. This is why you really want something heavy enough, it's the watts and the wire is relatively cheap.

Go here for a chart on wire gauge and current limits.
http://www.powerstream.com/Wire_Size.htm
It says 18 ga is good for 16A. So, yes, you'll be good with 300V rated wire there.

Actually, wire is rated for current carrying capacity and insulation breakdown voltage. A wire's insulation breakdown voltage is usually a function of insulator thickness. Current carrying capacity is a function of conductor diameter. Here's a link to a table that outline's the current carrying capacity of different wire gauges: http://www.powerstream.com/Wire_Size.htm. As one can ascertain from viewing this table, 22 AWG wire is rated to handle up to seven amps when used in chassis wiring.