Dynaco PAS I/O PCB Grounding

[petercapo]

I'm working on an I/O PCB (ExpressPCB) for my Dynaco PAS to replace the original jacks. At the moment, my "design" utilizes a ground plane foil on the inside. I am wondering if there might be a good reason not to use a ground plane here and if just daisy-chaining a wire through all the ground lugs might be better (though the ground plane foil is much more convenient and does not add to the cost).

There are other replacement I/O PCBs available for the PAS that also use a ground plane foil to some extent. But, my ground plane has much more area than some of the others. Does this matter?

This is actually my second rebuild of this PAS. I had a problem of hum increasing with the volume control in the first rebuild. For the first rebuild, the I/O PCB ground plane was in direct contact with the back panel. For this second rebuild, I was going to try it with the new I/O PCB ground plane not contacting the back panel and with a wire running from the ground plane foil to a star ground elsewhere (closest thing I can get to a star ground, anyway).

Thoughts?

Thanks.
Peter

[TerrySmith]

Yes, isolating the ground makes a big difference in the PAS preamps. I usually just etch off all the copper on a pcb, drill what I need and just wire the gnd lugs together. Using the foil as a ground plane is a good idea, however you're at the mercy of the quality of the jacks themselves.

[petercapo]

I read something about how ground planes are not optimal for audio circuits, something to the effect suggesting there could be local ground loops on the plane, how the ground current(s) flow (eddy currents?) or something like that. Not sure that it really matters much in this case, anyway. But, in addition to isolating the I/O from the back panel, I still wonder if daisy-chaining a wire might further reduce the possibility of hum. On the other hand, with broad ground plane coverage, perhaps the ground plane might provide some shielding from EMI at the openings on the back panel...

[snitch56]

I had the same question when I rebuilt a PAT4, so I just used both the ground plane and chained them together. I did isolate the phono inputs on the left with the tape head and special inputs (with nylon washers) to see if it made a difference. There was no difference at all. Seems to work good.

[petercapo]

Yeah, a lot of folks use the ground plane. I am sure it's fine.