Speaker jack ground

[g-man]

Deleted

[pompeiisneaks]

I need to start doing this, I've always been lazy and let the jack connection to the chassis provide the backup ground, but from what I gather the right way to do it is to ground it at the same potential as the power side of things, but I can't remember where I read/saw this.  It was on a recent layout for an amp and they were pointing that out.

~Phil

[drgonzonm]

It is not necessary to ground your output jack.
Yet, why deviate from the original design?  where the output jack provided a ground.   
As an example of an amp that that does not ground the output jack, Look in the amp tool section look at Stromberg-Carlson amp, it has a balanced output, that allows the user to set up the amp without a ground. (That amp does have NFB, but it has dedicated winding).  In that particular amp, one tap of the secondary was grounded by choice per note 10. 

[labb]

I think that in the early versions of the fender deluxe the OT ground was the frame of the transformer. Did not have a ground wire to go to the output jack. I have grounded speaker jacks by just the jack mounted to the chassis, jack mounted to chassis and ground wire run to the amp power end ground, jack isolated from chassis and just the OT ground wire, and the jack isolated from chassis and a ground wire run to the power end ground and I can tell no difference.

[sluckey]

so I'm wondering if that ground is actually needed. This amp doesn't have a negative feedback loop. I guess you would have to have it grounded if there was a NFB circuit?

That's your answer. No NFB, no ground needed. Got NFB that comes from the OT secondary, got to ground the OT secondary.

[g-man]

Deleted

[PRR]

You want it grounded in-case the OT gets an internal short and puts 400V on the secondary and speaker line. This is probably mandated by safety agencies. What you do in DIY is your own choice. But I see no reason to un-ground it.

The usual NFB affairs expect the secondary to be grounded, and preferably to somewhere near where NFB returns in the tube before the power tubes. But since signal levels are high here, and you have not(?) put your rectifier spikes through chassis, it may not be critical, and power ground rail may be fine.

[EKDENTON]

PRR, aren't  they  talking about the ground at the speaker jack, the OT rather than the PT?

[MFowler]

Ground the speaker jacks to the B+ cap ground point.

[jojokeo]

Ground the speaker jacks to the B+ cap ground point.

+1
There are high currents in the OT secondary. Do not ground it anywhere near a preamp ground and why multiple ground points in a chassis is asking for trouble in noise and oscillation issues. In general - amp signal grounds are "returns" and they also have currents in them and this is not the same as chassis ground. Ground is NOT some mythical place where everything goes to die into a black hole abyss never to be seen again.

Another point of interest: yes you don't have to ground your preamp pots when they have the ground lug soldered to their backs, using Switchcraft input jacks, etc...BUT if anything comes loose or develops a tiny bit of corrosion - which does happen a lot - then your circuit and live or recording performance is jeopardized rendering your amp a failure or being embarrassed because Mr Murphy's Law is always lurking to bite you in the ass at the worst possible moments. The lesson is to mind your grounds properly and carefully.