Which is better for cables FEP or PTFE

FEP by a margin,
don't know why and don't care it just is and dialectric is key to any electronically generated signal transmission - air is the best dialectric (Heaviside) but as I understand it, a digital conductor should be equidistant from it's sheild, so needs a dialectric to keep it in a centred position but then again some say this is b/s and no sheild is nec. - whatever, you can't go wrong using FEP.
 
kuribo said:
If you believe the lowest dielectric constant is best
Why would you believe that? The usual requirement is for a 75ohm characteristic impedance, and reasonable screening. Given that these links are usually short, almost any reasonable quality 75ohm coax should do. Frequency components only go up to VHF, so not very demanding.

There may be a very slight advantage in using a slightly lossy cable, as that will help to damp down any reflections due to poor termination
 
I said "why would you", not "why do you". I was leaving open the possibility of your current belief by questioning the reasons for such a belief, were it to be true.

Perhaps you could enlighten me. Given that you don't believe it yourself, I can only assume that you have heard others say it. Did they give reasons for their belief?
 
OK. Here is what I found in a 6moons cable review (so usual 6moons pinch of salt needed):
"The 'Anti-Compression Technology' is used in all of ZCable's current interconnects and digital cables including the Live v5, Live Ref1, Digital Duet, Digital Ref1 as well as the new Passion Ref1 speaker cables. A.C.T has to do with the interaction between the dielectric and the signal's electric charge. We know that any good musical cable should have a low dielectric constant. As the dielectric constant increases -- and if all other factors remain unchanged -- the electric flux density increases. This causes cables to hold their electric charge (or quantities thereof) for long periods of time.

Simply put, high dielectric constants cause signal distortion. Almost all audio cable implement their dielectric in such a way as to have a dielectric constant of 2.0 to 3.4. The following are the most commonly used dielectrics and their dielectric constants: PVC (3.4), Polyethylene (2.2), PTFE Teflon (2.0) and FEP Teflon (2.1). With ZCable's 'Anti-Compression Technology', our cables have an approximate dielectric constant of 1.3. [While the general value data here is perfectly factual, the preceding claim that most all audio cables exhibit dielectric constants greater than two is not where superior cables are concerned. Most bona fide HighEnd designs based on actual engineering use variations on air dielectric schemes to reduce their dielectric constant to below 1.6. ZCable is certainly not alone in knowing about the deleterious time smearing effects that insulation-induced signal absorption and re-release causes - Ed.]

Secondarily, as we tested dielectrics and their applications, we found a subjective aspect to do with signal glare and harshness. As we experimented with reducing the dielectric constant, we simultaneously discovered a way to reduce the glare and bite which many audio systems exhibit as the signal compresses during music passages of high dynamics or transients.

Lastly, we have discovered that the ratio of dielectric versus conductor quantity also influences the naturalness of the sound. Our cables use a very high conductor-to-dielectric ratio to give greater body and better dynamics while decreasing dielectric interaction. However, it is very difficult to increase conductor amounts while maintaining overall design and sonic balance. In other words, it takes plenty of trial and error to get it right.
I note there is assertion but no explanation. The words they use might be sufficient to appear to be an explanation to someone who, like them, doesn't know what they are talking about. They may be talking about Dielectric Absoption, but clearly not understanding it.
 

coresta

Member
2005-03-20 10:31 pm
Paris
Mmmh, seems to be only a "different" explanation of the Z transmission line formula ... where the lower the distance between conductors, the lower the impedance of the transmission line. Look at 75 and 50ohms coax : the 50 ohms one is norrower insulated the the 75 one ... :D
 
If you believe the lowest dielectric constant is best, then PTFE is better than FEP.

Also, FEP has a much higher (relative) Dissipation Factor than PTFE. So, lower DC, lower DF...a better insulation...right?.
Certainly in audio applications. Interestingly, as I think someone already pointed out, most teflon insulated CAT5 plenum cable etc. seem to have FEP insulation. Other factors at play I'm sure.
 
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FWIW,
back home from hospital after arrhythmia heart problems (going back next week) I made a discovery useful for those who make their own cables.

The drip and oxygen tubing was made of - FEP. It's easy to identify as it is much clearer and has a blueish tinge whereas TEFLON which has a slightly milky colour.

The oxygen tubing is about 5mm and 3 metres long before branching into much smaller gauge. This will be perfect for making air/FEP speaker cables.

Used once for each patient it is then thrown away - I just need to convince the nursing staff to save another 7 pieces for me rather than throwing it into the poubelle sac/rubbish bin.
 
Also, FEP has a much higher (relative) Dissipation Factor than PTFE. So, lower DC, lower DF...a better insulation...right?.
Certainly in audio applications. Interestingly, as I think someone already pointed out, most teflon insulated CAT5 plenum cable etc. seem to have FEP insulation. Other factors at play I'm sure.
Gigabit rate Ethernet signals are very fussy about cable loss, impedance and crosstalk. Fortunately they don't read cable salesmens BS