I bought 4 metres of this on a whim and thought I'd give it a try. I soldered on a brace of Neutriks (silver solder), checked all parameters (resistances & capacitance) and used it directly between my quitar and amp.
Making statements without context is difficult so I A/B'ed it numerous times to an old reference cable I have, (very transparent, clear, almost like having a buffer on, 2 solid copper cores, stiff as a coat hanger and not made any more :) ).
As others, I too have found that in this application there is an apparent volume loss with the Corona (apt name but I guess chosen before C19 was a thing, otherwise it would've been negative advertising). It's not a huge loss but is very detectable to me. It appears that the lows and low-mids are less pronounced and defined perhaps leading to the effect that the highs and high-mids in comparison are put more into prominence. The highs are not shrill but seems quite sweet to my ears actually. I would not say that this cable gives the a guitar a "hifi" sound: in my imagination more treble response, perhaps tending towards shrill would be necessary for this adjective to hold.
I don't know if the loss of lows contributes to the apparent loss of volume. From a sonic point of view the Corona seems more controlled & restrained than the reference cable I'm comparing it to (Two Rock Crystal Clear), which in comparison sounds more dynamic, alive or uncontolled. (Forgive my use of adjectives - this is all very subjective of course).
There are many folks that might like this "sound" (ok, filter). It isn't bad to my ears but personally I am more happy with the more neutral responses of the LLX and XXL cables also from Sommer. I can't explain the reason for the EQ I think I'm hearing: the cable capacitance can't explain it. In a live situation I could see that this reduction of lows and low mids could help a lot in cutting through the mush but of course amp volume and tone controls can also be effectively used to EQ for this.
Anyway not a bad sounding cable, just not EQ'ed for my taste. I might try it post buffer as a patch cable wiring on a pedalboard and I will certainly use it with some RCA connectors in a couple if HiFi applications in the house where I believe it will (might) give sonic improvements.
The cable does look great but it is spendy compared to other Sommer cables that imho are more suitable to pre-buffer instrument applications.
I couldn't imagine use of this cable with a passive (non-active) bass but I bet there are those out there who have already & successfully proven me wrong :)
So my advice, in a line & delivered with a pinch of salt: Save your money & buy the XXL or LLX instead.