It is a switching method where, in the bypass mode, the signal goes directly from the input jack through the switch to the output jack with no connection to the circuitry in the box. In effect, it is a straight wire through the box and does not degrade the signal because there is only the micro-ohm resistance of the jacks, wires and switches inline with the signal.
Is it necessary?
no. but not all buffered bypasses are created equal. if there weren't many buffered bypasses out there that didn't color the signal, there would be no need for true bypass.
Mind you.... I am NO expert when it comes to this shit. But this is what I believe about true bypass, and all the hype about it. Noob pedal buyers and not so noob users don't know jack about what really goes on inside the equipment. So they buy into the hype of having every pedal made ''true bypass'' whether they need it or not. All in an effort to have a cleaner ''uncolored'' signal from the guitar when the pedals is off.
I've actually gone to a true bypass looper to get the bulk of my pedals out of the signal path and it sounds pretty good. I was reading somewhere (another forum actually) where they felts it was good to have a buffered pedal at the end of the signal chain.
its good to have a buffer somewhere. both my tuner and my delay are buffered.
the overall quality of the pedals from that era is superior to the mainstream pedals we can buy today from the same makers.
crux of the biscuit.
I'm pretty sure the overall quality of the pedal is more important than 'true bypass' is. All I know is many of the classic guitar tones from the 60s & 70's that are so revered today were not performed on 'true bypass' pedals, though the overall quality of the pedals from that era is superior to the mainstream pedals we can buy today from the same makers.
My tuner is 'true bypass' and both my VS pedals are buffered....