• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Teflon (FEP) wire find!

I was shopping for some Teflon wire and not liking the prices... Then I go into my garage where I have a dozen or more 1000 foot spools of cat 6 CMP plenum rated Ethernet cable. (I was working with a local builder about 10 years ago to pre-wire his houses for video and LAN).

I read the boxes, and all the insulation is FEP and the wire is pure copper! And the pairs are impeccably twisted just perfectly. So now I have 96,000 feet of 23 AWG Teflon twisted wire pairs! I think that will last for a while.

23 AWG is rated for 4.7 amps in-chassis and has 20 ohms per 1000 feet. Note non-plenum rated UTP cable uses PVC insulation, so it has to say FEP insulation to be Teflon and be CMP rated. The outer jacket can be FEP or low smoke PVC, you're going to throw that out anyway. Only cat 6 is 23 AWG cat 5 is 24 AWG. There is a stripping thread under the jacket so its easy to pull off the outer jacket for many feet at a time. Good thing I saved all this wire.

Cat 6 also uses 4 different twits rates for the 4 pairs, blue is the tightest, then green, orange, then brown. Not sure why an Ethernet cable uses 4 different twist rates but thats even better for DIY projects.
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Cat 6 more tightly twisted than cat 5. All 4 pairs have the same impedance with 250MHz data down each so are twisted the same.

They are definitely 4 different twist rates, this is 500 mHz cable. the blue pair is obviously the tightest twist, about double the twists for the brown pair. Also the twists are so nicely done and dont fall apart you can use a pair as a single wire if you want to overrate the 4.7 amps of a single wire.
The different twist rates are by design.

There is a world outside of Audio (no, really!) and CATx cable was designed for data transmission by twisted differential pairs.

To reduce cross-talk between pairs, the twist rates differ to reduce inductive coupling between them. This becomes important for >= 1Gb/sec, since all 4 pairs are used at the same time, with different data.
I use plenum rated CAT5 and CAT6 for nearly all my internal wiring for signal. Love the stuff, and I have a huge box leftover from when I use to install the stuff.

Electricians are complaining that the price of FEP is exceeding the price of the copper. CAT 6 plenum has doubled in price over the past 5 years. There are only two plants making FEP in the world right now, Dupont and another. That explains the outrageous prices for Teflon hookup wire.


Paid Member
2003-06-12 7:04 pm
Maine USA
They are definitely 4 different twist rates, this is 500 mHz cable. the blue pair is obviously the tightest twist, about double the twists for the brown pair. Also the twists are so nicely done....

If the twist rate were the SAME it is like no twist at all.

A single pair FAR from interference, each conductor gets on-average the same interference and this can be cancelled-out. Twist only has to be much tighter than the distance to the interference. Typically from a power line a few feet away into a mike cable. 6 twists per foot is fine.

When you put two (or more) pairs very adjacent, with SAME twist rate, one half-twist solid lays next to solid, next half-twist stripe lays next to stripe. You have NO average-out, full crosstalk.

Of course a 4-inch cable with staggered twist rate may not fully average out. But you don't get large crosstalk in a few inches.

Over a 300 foot 100m run the twist-rates will average out and crosstalk will be very low.

In audio the twist-stagger is mostly moot. I have run unbalanced signals through first cheap speaker lead and then into CAT3 TP to a non-differential input. Crosstalk was entirely dominated by the predicted parasitic resistance and more than low enough for my purpose (spaced-pair mikes in a modest room where "stereo" was all time-arrival not intensity difference).
What's the hype about PTFE over PVC besides PVC doesn't like to get hot?


For ethernet you are talking high frequency, which means insulation must be low-loss at 100MHz -- GHz frequencies, which means it must be a material that doesn't absorb moisture (water molecules are very lossy at RF, and also change the capacitance a lot).

Normal ethernet is polyethylene (PE), which is very hydrophobic compared to PVC. The jacket material is less important as its further from the high field strength area between the conductor pairs. RF coax dielectric is almost always PE or PTFE. For coax the jacket material is not important, there's no electric field there.
FEP is not PTFE, but both are fluorocarbons and branded Teflon.

There is a world of difference in dielectric absorption between PVC and fluorocarbons. That's the electrical side. On the safety side, PVC decomposes at much lower temps. than fluorocarbons. Those decomposition products are toxic gasses.

PVC does not produce toxic gases. Acidic, yes. But not toxic. While PTFE, or Ftoroplast, can produce nerve-paralytic gas, but on very high temperature.


Paid Member
2003-06-12 7:04 pm
Maine USA
I get that, and that makes sense, but I'm thinking more like in a tube amp for audio signal and B+... Seems not to make much difference?

The only proper wire for tube amps is Cloth Covered. Not the cloth-over-plastic that one warehouse sells, but the stuff that looks, feels, and tastes line an old Fender.

If you allow post-1930s materials into your amp, it probably does not matter what new-fangled stuff you use. Unless you are selling it: then your product is clearly superior.