Re-engineering the Cobra (Thanks to Henry Fellner)

Here is a new post after a long break (been busy at work). 

First of all, I would to thank reader Henry Fellner for starting me down this path with his post about removing the outer sheath and fluffing up the cable diameter. 

Experiments: I removed the outer PVC sheath from my 1.5m single pair. Then I tested the following combinations.

1. All original but without the outer PVC sheath. No audible change in sound.
2. Removed the inner 4mm diameter Silicone damper and replaced with same diameter Teflon tube. No audible change in sound. Hmm...
   
3. Replaced the 4mm diameter Teflon inner tube with 10mm diameter cotton braid. Voila, success.
   
4. Added outer sheath of 0.2mm thick clear Poly-olefin Heatshrink tube for protection of the Litz wire. Auditioned again to ensure no degradation from step 3.
   
5. Replaced the heatshrink in step 4 with thin Teflon translucent tubing. Auditioned again to ensure no degradation from step 3.

Note: Comparisons were done with an intact 1.5m pair. The final comparison was by A-B Single Blind test with a retired professional rock guitarist.

Note: The final cable (configuration no 4 above because the the outer sheath  is clear and heatshrinking makes the overall finish look 'professional'.

Note: Although I considered 10mm Teflon tube as internal damper but the following considerations discouraged me.

• Teflon has the similar dielectric constant as Silicon rubber. So, hardly an improvement.
  
• Thicker Teflon tubes of 10mm diameter available in the market are not very flexible. This will make for an difficult to connect cable in the cramped space. 
• If I choose very thin 10 mm Teflon tube for flexibility, the round shape of the cable will not be maintained over time.
  
• Actually, Teflon was my first choice because it is long lasting and tougher than cotton braid. 
• Cotton braid is super flexible, maintains its shape and has dielectric constant nearly the same as air.
  

And now to measurements.

• Capacitance reduced from 1.8nF/m to 1.2nF/m (35% reduction).
• My records showed a 45% reduction in Inductance as measured last year during my experiments but I could not replicate the measurements last week. I think my meter need to be calibrated 😞. So I will include Inductance measurements later after I verify the measurements.
  
• Overall cable diameter increased from 6mm to 12mm.

Note: The overall length of the cable is reduced by about 20% when the diameter is increased from 4mm to 10mm. I started with 1.5m length raw cable and ended with 1.2m of the re-engineered version. Do add in 20% to your required length if you are planning to do this.

I was so happy with results that, over the course of 2024, I converted the Cobra cables in my systems to the re-engineered version (one set of single run, one set of two parallel & one set of six parallel). One more set to go but I need to drill bigger holes in my cabinet first...😒

What next: Following the same logic, one can use 20mm or 25mm diameter cotton braid to further reduce Capacitance and Inductance. You can make imposing fire hose sized speaker cables if that tickles your fancy 😁.

Finally, thanks again Henry.