Tube amp wiring and temperatures

[teemumm]

When you are doing internal wiring (including heater wiring) what kind of wires you are using? Normal electrical wires with PVC-insulation are specified normally for temperature ranges -25-70 centigrades (-13 -158F). Do you think the wiring should stand higher temperatures in tube amps?

There are also other insulation types available like silicone and teflon that would stand much higher temperatures.

 

[scid714]

I believe that the temp rating corralates with the voltage rating. I would go for heavy Teflon insulation rated for 600v or higher. But I'm sure someone more knowledgeable than my self will chime in.

 

[Merlinb]

The max temperature quoted is normally for the conductor rather than the insulation. I've never seen PVC wire rated for less than 85 celsius. I wouldn't even give it a second thought.

 

[trobbins]

Of course in a valve amp, the cable insulation is typically exposed to high temp from outside the cable, not inside due to thermal heating from the wire current. But the cable temp rating is appropriate to consider, especially considering the aged, stiff and often degraded insulation found in old amps around the bases of the output valves.

Conductor temp ratings of 75, 90C and 110C are typical for AC mains cables where I am - with 75C probably being a standard for a couple of decades. Modern cables (even with the 75C rating) would likely do better at aging than that available a few decades ago, but the higher tech PVC's with 90+C rating should be fine if you can get them in small sizes. There certainly is an esoteric world of cable coverings and standards for specialist applications, of which telfon is one type of insulation pointed to.

 

[kevinkr]

I mostly use stranded teflon insulated wire of various gauges in my gear. Temperature ratings are much higher than PVC so no concern with the stuff even at the output tube sockets.

 

[Jaimo]

I use silver plated teflon wire that you can get from Apex Jr. and others in the vendor forum. You can also make up your own wire by using small diameter teflon tubing a la Morgan Jones.

 

[multi]

Small bore teflon tubing costs much more than using teflon coated wire.

 

[mark02131]

I found teflon wire is very hard to work with because it's so slippery. I use solid core cloth wire from tube depot. The cotton braid is woven over PVC insulated wire rated at 600 volts and 105 degrees

They also have aerospace grade, militery spec wire that I have had very good luck with. 600v high temp stuff.

 

[teemumm]

Actually I found this kind of wire from one supplier (www.elfa.se). Price was about 1eur/m for 0.75mm^2 wire. This should stand about 600V and 155 centigrades.

http://www.sibel.bg/upl_doc/RADOX 155_en.pdf

 

[trobbins]

I came across some Radox 125 - certainly good for wiring from hotter output tube sockets, and for HT wiring where you may want a bit more assurance. Even though it has class 5 flexibility, it was still a bit stiff, and not that easy to solder to - so perhaps be aware.