No doubt they work and enhance the overall listening pleasure. For those who are keen to fine tune and optimize their current hifi investment this is something you really must have.

A bit pricey therefore probably worthwhile if your hifi system value is at least 5 to 10 times or greater. Can be a bit unsightly as they are not that small.

I purchase a pair of the Zcable Ultra Z sleeves and a pair of Extra heavy after stumbling on the zcable website not so long ago. I bought this because I am convince of the technology used and thought I give it a try. Thankfully the results are very satisfying. I used the ultra on the CD interconnect and the preamp to power amp and the pair of extra heavy (incidentally cost USD399 each compared to the Ultra at USD299 each) on my speaker cables closer to the speaker end.

The immediate effect I heard is that the background is so much quieter and resulting in so much more detai being revealed and the high frequency is so much more airy. As far as voice is concerned the harmonic quality and texture is so much more natural and makes the music more involving.

Down at the low frequency, the bass is much more defined and distinct.

Sound stage and depth improved significantly as spatial resolution is now very much enhanced.

To ensure that it is not a placebo effect, I remove them after listening to them for more than 48 hours. Immediately the edginess and veiling effect come into play and makes listening more fatiguing, so after half hour or so the z-sleeves are back on. The thing to try now is to switch between the Ultra and Extra heavy to see if a different arrangement will produce a different effect. Maybe there are hidden surprises.

Customer Service

Excellent.