Starting first restore

peterh wrote:Is the preamp AND st70 both grounded via 3 prong cables ?
An additional cable, connected in cover screws could be tested.
Grounding stuff with the signal cables only is a way to introduce hum.

Peter W. wrote:

peterh wrote:Is the preamp AND st70 both grounded via 3 prong cables ?
An additional cable, connected in cover screws could be tested.
Grounding stuff with the signal cables only is a way to introduce hum.

Without being the slightest bit snarky, I am of the opinion that Europeans, what with IEC mandated grounded line-cords simply do not understand the potential (pun intended) issues with US grounded receptacles.

May I suggest, with all due respect, that you not opine on US systems unless/until you have a better understanding of these issues. For the most part, multiple equipment line-cord grounds, unless very carefully managed and *designed into* the equipment are a bad idea, at least in the US.

https://en.wikipedia.org/wiki/File:TT-earthing.svg is what we use here in the US.   Neutral and ground are bonded in the panel and so there is very nearly always some potential to-ground for obvious reasons. And a bad neutral, while not ideal, is covered by the local ground. But, this is why grounds must be so carefully managed.

From my understanding, you use (mostly) this:    https://en.wikipedia.org/wiki/File:TN-C-S-earthing.svg   Please correct me if this is a false impression.

Accordingly, local differences in potential are less of an issue for you, whereas a bad neutral is not good at all. So, there are very real functional differences in how things work.

peterh wrote:
Equipment in europe has both incoming AC lines isolated from ground, all AC is
"floating" as regards to chassies and or signal ground.  No special treatment
of "live" or "neutral" is done, all wires are considered "live" for security purposes.
The ground cable in the outlet that has them is not connected to either
wire but to a ground post in the electric distribution center.

Understood. In such a case, a bad neutral will lead to havoc with the entire live circuit above-ground thereby. On this side of the pond, ground and neutral are bonded in the panel, and local grounds are required.

As for the equipments, signal ground and chassie ground  may be separated
by some amount, but neither is allowed to be connected to any mains AC line.

Also understood. But, component failure could lead to mains-potential on the signal lines given that Euro systems have what amounts to an isolated ground system - not a local ground.

Interconnecting equipment by the groundline is common practice and will
normally prevent hum issues due to leakage of AC internally. Additional
interconnects of equipment done in industrial racking or with external
"grounding cables" helps to prevent ground loops.

Yes, and here is the biggest difference - under the system you describe, there is, ultimately, a single ground option which, perforce is at a single potential. So, loop grounding vs. star grounding is less of an issue than here. In the US, no two receptacles will have exactly the same ground potential, nor will the neutral necessarily be at the same potential as the ground. The difference may be in millivolts, but it is real enough to cause all sorts of hum issues THAT ARE NOT DUE TO LEAKAGE.

I am not aware of US equipment or AC distribution methods. But apart
from "death caps" used in some older stuff i do think AC lines are
floating relative chassies and signal grounds.

Death Caps is an apt descriptive, but largely replaced these days by properly rated caps. Only the hot is isolated, as noted before. Just as an example: We have a central ground-rod our incoming service. We also ground to the water utility line (cast iron, 2 meters underground, 100' to a ductile-iron main. Our service (overhead triplex aluminum) consists of two hots (120/240) and a neutral. The transformer is isolated but the shell is grounded. and it is fed by 13,200 VAC single-phase power. The neutral is also overhead, and grounded at each transformer, bonded to ground in our panel, and bonded to the local ground rod and water-service as well.

Leaving units floating with no ground whatsoever will leave them humming
at half mains voltage, some units may leak more to one ac-conductor
then the other, creating a weak but real hum-loop. This is easily observed
by slight touching with a dry finger, any "humming" will be an indication
of a floating amp.

Only if there is leakage. But, in the US, as there are multiple ground options, and as grounding is also local, picking a *SINGLE* ground to bleed off any leakage will effectively eliminate ground loops and the associated hum. having two separate ground options will create a loop. Why it is that Star-Grounding or single-ended series grounding is typical here. If you look at most US designs, the signal ground and the chassis ground are one-and-the-same. Exceptions include head and phono amps, but even then not in every case. This puts _ALL_ equipment grounds at equal potential within the system if properly laid out. Where things go bad is when the cable shields doing the grounding from A to B are usurped by an extraneous ground. Or these shields are damaged, or not making good contact, or any of a dozen other ways they could fail. But the idea is to have them NOT fail, not to add more grounds.

As  we also have a lethal AC in europe ( 230V ) it's even more importent to
make sure that chassies are not only isolated but also grounded to prevent
accidents even if faults occurs in the equipments.

Do interconnect your amps  chassies. This will normally decrease hum, any
residual hum is due to other reasons. And its easy to implement ( or remove)

Each component in my systems are all grounded to a single ground in a single-ended series-ground configuration. The exceptions to this are the turntables, where the chassis grounds are sent to the left phono headshell. I do not have hum problems.

Peter W. wrote:Some snippage, some interpolations.

peterh wrote:
Equipment in europe has both incoming AC lines isolated from ground, all AC is
"floating" as regards to chassies and or signal ground.  No special treatment
of "live" or "neutral" is done, all wires are considered "live" for security purposes.
The ground cable in the outlet that has them is not connected to either
wire but to a ground post in the electric distribution center.

Understood. In such a case, a bad neutral will lead to havoc with the entire live circuit above-ground thereby. On this side of the pond, ground and neutral are bonded in the panel, and local grounds are required.

As for the equipments, signal ground and chassie ground  may be separated
by some amount, but neither is allowed to be connected to any mains AC line.

Also understood. But, component failure could lead to mains-potential on the signal lines given that Euro systems have what amounts to an isolated ground system - not a local ground.

Interconnecting equipment by the groundline is common practice and will
normally prevent hum issues due to leakage of AC internally. Additional
interconnects of equipment done in industrial racking or with external
"grounding cables" helps to prevent ground loops.

Yes, and here is the biggest difference - under the system you describe, there is, ultimately, a single ground option which, perforce is at a single potential. So, loop grounding vs. star grounding is less of an issue than here. In the US, no two receptacles will  have exactly the same ground potential, nor will the neutral necessarily be at the same potential as the ground. The difference may be in millivolts, but it is real enough to cause all sorts of hum issues THAT ARE NOT DUE TO LEAKAGE.

I am not aware of US equipment or AC distribution methods. But apart
from "death caps" used in some older stuff i do think AC lines are
floating relative chassies and signal grounds.

Death Caps is an apt descriptive, but largely replaced these days by properly rated caps. Only the hot is isolated, as noted before. Just as an example: We have a central ground-rod our incoming service. We also ground to the water utility line (cast iron, 2 meters underground, 100' to a ductile-iron main. Our service (overhead triplex aluminum) consists of two hots (120/240) and a neutral. The transformer is isolated but the shell is grounded. and it is fed by 13,200 VAC single-phase power. The neutral is also overhead, and grounded at each transformer, bonded to ground in our panel, and bonded to the local ground rod and water-service as well.  

Leaving units floating with no ground whatsoever will leave them humming
at half mains voltage, some units may leak more to one ac-conductor
then the other, creating a weak but real hum-loop. This is easily observed
by slight touching with a dry finger, any "humming" will be an indication
of a floating amp.

Only if there is leakage. But, in the US, as there are multiple ground options, and as grounding is also local, picking a *SINGLE* ground to bleed off any leakage will effectively eliminate ground loops and the associated hum. having two separate ground options will create a loop. Why it is that Star-Grounding or single-ended series grounding is typical here. If you look at most US designs, the signal ground and the chassis ground are one-and-the-same. Exceptions include head and phono amps, but even then not in every case. This puts _ALL_ equipment grounds at equal potential within the system if properly laid out. Where things go bad is when the cable shields doing the grounding from A to B are usurped by an extraneous ground. Or these shields are damaged, or not making good contact, or any of a dozen other ways they could fail. But the idea is to have them NOT fail, not to add more grounds.  

As  we also have a lethal AC in europe ( 230V ) it's even more importent to
make sure that chassies are not only isolated but also grounded to prevent
accidents even if faults occurs in the equipments.

Do interconnect your amps  chassies. This will normally decrease hum, any
residual hum is due to other reasons. And its easy to implement ( or remove)

Each component in my systems are all grounded to a single ground in a single-ended series-ground configuration. The exceptions to this are the turntables, where the chassis grounds are sent to the left phono headshell. I do not have hum problems.

ttownscott wrote:Yes. It is quiet now that I have changed out the cable.
After the one in the picture, I picked up a shielded cable on Amazon that two people on another forum said eliminated their hum. It further reduced the hum on my amp as well. It is totally gone now.

https://www.amazon.com/gp/product/B016QVZEZM/

ttownscott wrote:Now that I have been living with it for a month, I'm wondering about what would be a good upgrade.
I have two pairs of 12AU7 type tubes, so I was of course thinking to pick up the VTA board probably with a cap upgrade.

Not sure if upgrading the PA060 and possibly the choke would buy me any performance increase.

another thought is to see if it sells for say $800 and build the vta-70. It would be fresh, but I would have to buy output tubes and maybe a cage.

As it is now, I am happy with the chassis and the nice but vintage look to my cage. Also the triode swich is not a big appeal to me. Trying KT88's after the EL34's wear out sounds like something I would try.

ttownscott wrote:Now that I have been living with it for a month, I'm wondering about what would be a good upgrade.
I have two pairs of 12AU7 type tubes, so I was of course thinking to pick up the VTA board probably with a cap upgrade.

Not sure if upgrading the PA060 and possibly the choke would buy me any performance increase.

another thought is to see if it sells for say $800 and build the vta-70. It would be fresh, but I would have to buy output tubes and maybe a cage.

As it is now, I am happy with the chassis and the nice but vintage look to my cage. Also the triode swich is not a big appeal to me. Trying KT88's after the EL34's wear out sounds like something I would try.