About silicon wire

[GainFreak]

Recently I decided ti use some silicon stranded wire for a build and my experience was it had many advantages over the "regular" wire.
It's easy to twist, easy to strip, would stay in fixed position and the insulation doesn't melt at all. In fact I tried an open flame from a lighter on it and it wouldn't change a bit after 10 or more seconds. So my question is since silicon wire has some obvious advantages over the "regular" wire why I don't see any used in amps and transformers? Is it just that I liked it or I am missing something here?

[Pedro Vecino]

Wich gauge? (AWG)
I've only experienced with narrow gauges (21 or similar) and the only real advantage I find is flexibility (can reduce certain microphonic symptoms in some circumstances) but overall I do not like. More important to me is the difficulty involved in obtaining a particular final position in the wires. Sometimes impossible.
I imagine there are different types (different stiffness), but that is my experience.

[Chuck H]

I used the flexible stuff that Pedro is talking about. I think it was made for test leads, ergo, flexible. I'm sure "they" also make a NOT so flexible silicone jacketed wire. I think the main reason you don't see it used more often is expense. My soldering skills are mediocre so I did enjoy the heat resistant jacket The last time I spooled up I bought irradiated PVC which, while not nearly as heat resistant only suffers about half the "shrink" of regular PVC jacket. Much more affordable and it works just fine. Since it performs 'well enough' for even me to get good results, there's a real advantage to the cost saving. I can get more colors and I worry less about waste. If cost is literally of no concern, why not buy the silicone if you like it. For myself, I need to look at my bank account and decide if I want to spend $400 to restock spools when $150 will got the job done.

[loudthud]

GainFreak, what are the temperature and Voltage ratings of the wire you used?

[GainFreak]

There's the following printed on the insulation: "SILTOP VDE Reg. Nr 7696". If you google it the first result returned is the manufacturer. This is the datasheet:

http://www.schaffroth.de/fileadmin/c...rmation_01.pdf

A datasheet from another manufacturer:

http://www.connectsolutions.de/download/222.pdf

Breakdown voltage : 5000 V
Test voltage : 2000 V
Operating voltage : Uo/U 300/500 V

It looks like "N2GFAF" is some standard european stuff because if you google it many manufacturers show up.

Data sheet says +180 degC however the insulation wouldn't change a bit when exposed to an open flame from a lighter which is way above that I guess.

[Chuck H]

...however the insulation wouldn't change a bit when exposed to an open flame...

Perhaps not visibly. But how do we know the jacket didn't suffer some change that makes it more prone to conductivity? I (for one) have never tested for that and I'm not sure the bench gear I have is suitable for such tests that may be high voltage dependent. The rating is probably there for a reason. Not many manufacturers spec a rating below their products ability.

[GainFreak]

But how do we know the jacket didn't suffer some change that makes it more prone to conductivity?

I don't know that but if you have an open flame in an amp this is the last thing we should worry about
The cables are rated for 180 degC which means they can handlemore but even that is way above the temperatures you can measure inside a tube amp.
Also all those voltage ratings are usually for AC and many Amperes so I don't think I should worry about either.

[Mick Bailey]

My experience of silicone insulation is that it's more susceptible to cutting through - say on a sharp edge, and not as mechanically robust as other types. If there's a slight nick it will open up pretty quickly under strain or flexing. There are different types though, and where higher mechanical strength is required the silicone is impregnated in glass-fibre. Amp builders generally go for PTFE insulation, and this has the advantage of high mechanical durability as well as heat and chemical resistance.

[GainFreak]

Obviously there are different types of silicon insulation because the one I'm using is more like rubber and would stretch if pulled but definitely not break even when extremely bent.

[Chuck H]

I think Mick is referring strictly to abrasion resistance and not flexibility. He's not suggesting it will crack, he's saying it if it gets nicked or scratched it's more likely to tear. This could happen from inside the jacket (broken stranding) as well as outside (vibrating against unpolished metal parts). But it does seem like an extreme consideration in the real world.

I liked the PTFE jacket too. What I noticed first was how thin it was for the same voltage rating as PVC. I don't get this. I would think that space is space. That is, I would think the distance a voltage can jump an insulator has more to do with the space it occupies rather than the material itself if they can simply be defined as non conductive, but I guess that isn't the case. So, is PVC jacket more conductive than PTFE jacket? I imagine the difference to be some regulated spec of relative goodness at a fixed condition because PVC will carbonize at a much lower temperature than silicone or PTFE. But I'm just guessing.

Hey! At least we're not still stuck with waxed cloth.

[g1]

So, is PVC jacket more conductive than PTFE jacket? I imagine the difference to be some regulated spec of relative goodness at a fixed condition

I believe the spec for dielectric strength is V/Mil (volts per thousandth of inch)

[trobbins]

I have just got some 24AWG 3kVDC rated coming in - but that is for the specific application of P-P wiring between valve sockets and an OT that is some distance away. I wanted to twist the PP and B+ wires to minimise coupling to other circuitry, but also to minimise capacitance between wires and to chassis as its a Williamson amp. The wire has a large insulation diameter, and the voltage rating suits the P-P application.

[trobbins]

The wire has a large insulation diameter ....

Like all photos for items on sale, the perspective of size can catch one out. The received silicone rubber insulated wire is about about 1.5mm diameter - a little smaller than what I had anticipated. I guess I was thinking of a diameter closer to the typical size of multimeter probe wire. Still - it should do the job.