Heater/Filament wire gauge

Haych

The last thing I need to do on my HP Princeton building is wire up the heater connections.

The supplied wire in the kit is a bit like telephone cable, very thick with a rubber insulation and a cotton overbraid.  It doesn't twist at all well and I reckon wiring up the tube sockets will be very difficult as it's quite a heavy gauge, especially the preamp sockets!

In terms of AWG, what's an appropriate gauge wire to use for this application?

Thanks in advance.

RiftAmps

18awg is standard

Haych

Thank you

jpfamps

Assuming the usual arrangement where the filaments are daisy chained in parallel, then you can use thinner wire for the pre-amp valves as current passing through the filament wire diminishes down the daisy chain.

18 AWG is rated to handle 16 A for chassis wiring (and this rating is conservative).

 So say 4 x 12A*7s and 2 x 6V6 would require 2.1 A of filament current in total (4 x 300 mA  + 2 x 450 mA), and 1.2 A for the 4 pre-amp valves. 

18 AWG is total over kill (not a bad idea mind), but you could use 18 AWG for the power valves and say 22 AWG (current rating 7A) for the pre-amp valves perfectly safely.

Haych

Again, thank you. It’s all very useful information. 

Will the the fact that I’m using 6L6s make any difference at all?

Modulus_Amps

You still only need 3 Amp current rating, so 22AWG would be fine and easy to handle. Cloth covered wire is commonly available in 20AWG which would be easier to work with too.

If in doubt read the gauge on the heater wire coming out the transformers. do not use smaller than that for the power valves, for the pre-amp valves 20 - 22 AWG is totally fine.

Modulus_Amps

Valve data sheets always list the heater current required if you are ever stuck trying to work this stuff out. Most transformer builders I have used use tri-rated cable that is always marked with the wire gauge on the wire, so using the same gauge is always the safest way to go for the first few connections in a daisy chain.

jpfamps

Haych said:

Again, thank you. It’s all very useful information. 

Will the the fact that I’m using 6L6s make any difference at all?

6L6s require 0.9 A of filament current each c.f. 0.45 A each for 6V6s, so 3 A total as stated above.

Haych

Awesome, thanks y'all!