Grounding Metal Outlet Boxes and Isolated Ground Receptacles

bflowers,

IF the dedicated branch circuit wiring for the power amp is braided (hot, neutral, an IG ground conductors braided) together that might be the problem. Think of it as an 8ft shielded power cord. ( 3 braided conductors inside a steel outer shield) With the braid basically you have 1 hot ungrounded conductor, (120V above ground potential), and 2 conductors at ground potential. (The neutral, the grounded conductor, and the equipment ground, the grounding conductor.)
Most power amps do not like shielded power cords. My experience it sucks the air from the sound of the amp.

For a couple hundred dollars labor plus material you could find out for sure if my theory is correct.

Have your electrician pull out the braided wire from the conduit that feeds the Boulder 3060 power amp.

You didn’t say the size of the conduits used.... I am going to assume they are 1/2" EMT. https://www.google.com/shopping/product/15351473063369031769?lsf=seller:8740,store:11486162617141277...
Or possibly 1/2" flexible metal conduit.

For the new wire that will be pulled back in the conduit use solid core, not stranded, THHN/THWN. (Stranded wire can smear the sound)

Ask the electrician to slightly, to moderately, twist the hot and neutral conductors together the entire length of the conduit run. The IG equipment ground conductor will be pulled straight along side the hot and neutral twisted pair.


Read pages 16 through 35. Mainly 31 through 35.

https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

bflowers said,
 In metal conduits. Single run of 12G braided wire in each conduit. Run from subpanel is <8 ft in all cases. Probably 20 or so lines coming of the subpanel. Don't know about the interconnects. There are 2 legs, but all my equipment fits on one leg.

There are 2 legs, but all my equipment fits on one leg

I just learned from almarg the amp is 240V.  Hopefully almarg will read your posts on this thread. He may have some thoughts.
Jim

 

Jim, thanks for calling this thread thread to my attention, via your post in the directional interconnects thread. My response there on 12-6-2016, near the bottom of page 3 if posts are sorted most recent last, may be of interest to some here.

Stickman’s wiring may already have been finalized, but FWIW re:

Jea48 11-14-2016

I would wonder if the floating insulated wire might act as an antenna and pick up air born RFI. I would probably connect the end at the panel to the ground bar. Nothing wrong with that as far as a code issue. Ask your electrician if he has a problem with it.

It would be nice to hear from Al, (almarg), what he thinks. Would he connect the end of the spare insulated wire at the electrical panel to the ground bar, or leave it floating above ground?

I agree. Antenna and RFI effects are always hard to predict, of course, and it might not matter either way. But grounding the wire at the panel, in addition to perhaps reducing RFI pickup, would add a bit of capacitance between the AC conductors and ground that I suppose might provide at least a slight benefit in terms of filtering RF noise that may be present on the incoming AC.

Regarding Bflowers issue, the only thoughts that occur to me beyond what Jim has said are:

1)It would probably be a good idea to measure the AC voltages (120 volts on each leg, relative to neutral, and the 240 volt difference between the legs), during typical listening hours. If practical it would be preferable to do that while the system is powered up and playing music at normal volumes.

2)Regarding:

Bflowers 12-1-2016
BTW, had serious ground loops in the old room, but the Boulder gear was fairly impervious to it. I demoed a single ended Lamm amp and it buzzed like a fiend!

Not sure which Lamm model you tried, but I see that the currently produced models that are described as single-ended provide unbalanced inputs on their XLR connectors. Which if connected to the balanced outputs of your Boulder preamp via an XLR cable would short the inverted signal on XLR pin 3 to the circuit grounds of both the amp and the preamp. Given the relatively low output impedance of the Boulder preamp (spec’d at 100 ohms, which probably corresponds to 50 ohms per leg), that could conceivably have resulted in the buzzing you heard. See this thread for an example of a situation in which exactly that occurred, although very different equipment was involved.

Also, while very unlikely it is conceivable that the output stage of the preamp which drives XLR pin 3 on each channel might have suffered some damage as a result of having that signal shorted to ground. So to be sure, subsequent to the Lamm audition did you put the older Boulder amp back in place, and find the system to perform the same as previously?

Good luck. Regards,
-- Al