persistent 60 cycle hum only on tube gear

As you've requested, I've turned my explanations into a blog post, with better explanations about the difference between running an isolated ground wire from the panel and creating a new grounding system. 

I even had AI create a graphic to help with the illustration. 

Enjoy! 

@atmasphere 

Here are the schematic diagrams for the ARC VT130 amp and the ARC SP-15 preamp.

https://www.arcdb.ws/model/VT130  (Click on VT130 schematic)

Note: It appears the circuit signal ground is connected solidly, directly, to the EGC grounded chassis. (Not good). Therein, signal ground is not connected, (for example), to a 10 ohm resistor then to the grounded chassis. 

B- of the DC power supplies is connected to a 10 ohm resistor (R88) then to the EGC grounded chassis. (Good design).  (EGC = Equipment Grounding Conductor)

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https://www.arcdb.ws/Database/SP15/ARC_SP15_schematic_and_parts_list.pdf  

Note the capacitors on the AC mains line input. One from Hot to EGC ground. One from the Neutral to EGC ground.  Could those be leaking AC current? Especially the one connected to the Hot conductor?

Note: The signal ground on the phono input runs through a couple of caps in parallel and then connect to the EGC grounded chassis. There is another cap used on the same signal ground to EGC grounded chassis by RCA line inputs.

  What if there is a small ac voltage present on the grounded chassis. Wouldn’t the caps pass AC current to the signal ground. Would that cause a 60Hz hum?

FYI The Branch circuit EGC is lifted at the wall outlet. Also worth noting who knows what's coming in on the wire from the ground rod outdoors. There could be a difference of potential, voltage, between the IG rod and the AC mains neutral conductor. (There are stay AC voltages all over the place in the earth)

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Erik,

Your exlanation is one of the best I’ve seen, and you are performing a great service to the community.  On my power cable page I warn people about defeating the ground on any power cables in their system.  I’ve yet to cover isoalted grounds.

In any case, I’m putting a link to your blog post on that page.

Cheers,

Thom @ Galibier Design

Great post @erik_squires , thank you.

@yesiam_a_pirate 

I suggest you watch this You Tube video on the Puritan Audio Laboratories GroundMaster.

Note: He says, Do not defeat the AC mains safety equipment ground.

Note: His mention of installing a Supplementary Ground Rod. This Is Not an Isolated Ground Rod. A Supplementary Ground Rod must be connected directly to the branch circuit EGC (Equipment Grounding Conductor) per NEC code for electrical safety. He should of mentioned that in the video.

For the Ground Master you can connect an additional ground wire from the ground rod to the Ground Master. One ground wire to the AC mains EGC connection in the wall outlet box. One for the Ground Master. 

https://www.youtube.com/watch?v=2G8-Z3BMDcw

FYI, "Supplementary" Ground Rod, is an old name used years ago replaced by,  "Auxiliary" Grounding Electrodes. Therein Auxiliary ground rod.

(NEC, 250.54)

If you must, use a ground cheater on the power cord(s) of the equipment to lift the ground from the chassis. (Not recommended for electrical safety though.) 

Hopefully @atmasphere will look at the schematic wiring diagrams I provided in my above post for your ARC equipment. 

@atmasphere said:

Does the amp make a buzz or hum without the preamp connected?

If yes, Is it both channels or just one?

If neither channel, The amp is OK.

You need to do this test. If you still have a buzz or hum with just the amp, (ICs not connected to inputs), 

You may need to use shorting plugs on the R & L inputs.

Still have buzz, hum? Try moving all the digital streaming equipment away from the amp and unplug it from the AC main oulet for the test.  

Read @bruce19 above post.

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