Well I guess that if you have a Gibson, a Marshall/Vox/Fender and a good guitar player, this plug won't be much of a change!

I don't know for sure, but from my relatively cynical perspective, it seems like yet another gimmick to wring a couple more bucks out of gear obsessed guitarists.

I mean, surely if you're in a context where this precise kind of thing matters, you're either recording with access to EQ/amp/mixer channels/processors/DAW that can 'sweeten' your 'tone' to your liking — not just to some preset, arbitrarily predetermined setting — or you're performing with sound reinforcement of similar capability.

I don't know. Really seems like crap to me.

Looks to me like that rotary switch just cycles through different capacitors. It's tantamount to changing/adding capacitors to the circuits inside your instrument. I doubt it's a terribly complicated circuit, so you could probably build a more flexible one with a wider range of values pretty cheaply yourself.

Neutrik generally doesn't come out with gimmicky crap, so this is a little surprising. I suppose it's smart - get a little cash out of the tone-obsessed guitar players, but even their graph does not show a huge different. It's not a scam (like Monster, Mogami....), but probably not really worth it.

You do KNOW that the super-premium cable makers have to be gunning to have exclusive rights to put these on their oxygen free cables!

Never used the plug but impedance CAN make a big difference in how a guitar sounds. Dynamic mics and to a lesser extent condenser mics also.

It would be resistors in parallel to get the impedance change rather than capacitors.

Do some cables sound better than others? I dunno for sure but some cables do sound like ass compared to others in my experience.

The Radial Dragster is another device to alter guitar impedance for tone and profit http://www.tonebone.com/tb-dragster.htm