@noromance - the purpose of the helix neutral is two fold
#1...
- to stop the alternating voltage in the signal wire from inducing "noise" into the neutral wire, which utlimately is fed back into the neutral side of the circuits of the connected components.
- Noise on the neutral side of the circuit impacts the ability of the circuit to perform as designed
- When used on all cables in a system noise is elimanated throughout the system.
Some say this is negligable, but at each "stage" that noise is amplified and as such creates a significant problem by the time it reaches the speakers.
The speakers have the highest voltages, so they make the biggest impact to the neutral side of the amplifier
On the power cable side of things - any noise on the neutral permates through the entire system via the attached components and contributes greatly to system wide noise issues
#2...
- The helix spiral acts like a faraday cage around the signal wire
- it minimizes the impact of "external noise" on the signal wire(s) by disrupting the "Space" around them
- a bit like a screen
Yes - Noise rejection is very good, both from external sources and internal cable signal induced noise
- e.g. I once held a standard turntable cable (i.e. from the MC cartridge to the phono) tightly n my fist, against a Helix power cable
- to even my surprise, whilst there was a very small amount of hum coming from the speakers is was only audible when the amp was turned to very high levels
Hope that helps - Steve