newbie question - SLO 100 grounding question

[GKWallace]

Hi there!
The short question is why would you use a shielded wire and not ground BOTH ends of the shielding?
I'm trying to understand exactly what's going on in the layouts and schematics of an SLO before I attempt a build. I've only built a JTM45 so my experience is very limited.
On every schematic and layout of an slo I've ever seen, pin 2 of V1 is wired to a variable resistor tab 2 with the center wire and the shielding is only grounded at the resistor end on tab 1.
Why?

[pdf64]

It eliminates the possibility of hum loops being created, with no apparent downsides.
What benefit do you perceive from connecting both ends to ground?

[GKWallace]

It eliminates the possibility of hum loops being created, with no apparent downsides.
What benefit do you perceive from connecting both ends to ground?

I really don't perceive anything other than a ground is not a ground unless is connected at both ends.
I had a feeling that might be the answer, but I don't know enough to assume anything.
Thank you so much for your speeding reply and the help.
Have a great Sunday!

[shooter]

a ground is not a ground unless is connected at both ends.

that's 2 grounds, when we ground a shield at only one end, think of it as an AC ground, NOT DC ground
AC "rides" on a DC potential, so any stray AC, get s "shorted" at the single solder point.


The math is sorta crazy but if you ground a wire at 2 ends, there is a chance because of wire length n resistance you "create" a DC potential one end to the other, then AC see's a chance to "jump on" and ping-pong along that potential.

[GKWallace]

a ground is not a ground unless is connected at both ends.

that's 2 grounds, when we ground a shield at only one end, think of it as an AC ground, NOT DC ground
AC "rides" on a DC potential, so any stray AC, get s "shorted" at the single solder point.


The math is sorta crazy but if you ground a wire at 2 ends, there is a chance because of wire length n resistance you "create" a DC potential one end to the other, then AC see's a chance to "jump on" and ping-pong along that potential.

Now that makes perfect sense.
I don't yet have an intuitive feel for differentiating AC and DC when looking at a schematic.
Truth be told, I have no use for yet another amp. I am fascinated by amp circuits. More to the point, bending components and soldering is an effective use of my OCD.

[Willabe]

The short question is why would you use a shielded wire and not ground BOTH ends of the shielding?

It will cause a ground loop that will probably cause noise/buzz.

Signal gets on the outer shield, rides down to the ground connection back through the chassis, goes back onto the outer shields other end and starts to ride back down again. Round and round she goes.

I've read that there's really 1 more part, that is at 1 moment, 1 end of the chassis shield connection looks like the least resistance to ground, then the next moment the other end looks like it has the lowest resistance and so signal riding on the shield keeps changing direction and that causes an ac signal frequency, modulation, being the speed of the switching direction. That's buzz; ac frequency.

And the shield is just that, a shield. It shields the inner center wire that has the signal on it. The shield is not for passing signal from 1 part of the circuit to the next part. It just sucks up any stray air born signal we don't want and bleeds it to ground to keep it from contaminating the ac signal we want. It shields it.   

[GKWallace]

Thanks for the explanation.
Thank you all for being so gracious in your replies.