With your latest experiment were you straight into the wall or into the Equitech? Didn’t last night you had no noise with the amps into the wall and no cheaters and the noise only came back when you connected the preamp. Do you think the problem could be the Equitech? If you have another power strip around you might try it with all three pieces. If you can get the amps to work quietly without the cheater plugs on their own then the BHK preamp just may not be the answer in your situation but there are a lot of other options out there. Though I still have mine it has been sitting since December.
That sure sounds like a grounding problem, open neutral, or neutral-hot leg swapped somewhere. Did you happen to check the outlets with a tester? How about turning every other breaker in the house off except for the line you are using?
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There’s a thread on them here somewhere. Try doing a search using D&D or Dutch & Dutch. For me they were the best solution for the system they are in. My stereo stack is in a closet on the other side of the room and I would have needed 32 foot or slightly longer speaker cables if I used passive speakers. I ended up using Belden BAV XLR’s to connect them to my BHK preamp. They are a great sounding set of speakers. I ended up adding a set of SVS 3000 stereo subs for some low volume listening fill. They are crisp and clean and will play as loud as you want. Being class D amps they also dont generate any noticeable heat.
Last experiment was straight into the wall.
I put a cheater on preamp first but hum was still there the minute I connected an IC from pre to amp. Putting cheaters on everything made it all quiet until pre power up
Having one of the tester just to plug into a wall receptacle is very helpful, in an instant it will tell you if the receptacle is wired properly and if there is a ground present.
I know polarity isn’t reversed and it cannot be an open neutral otherwise nothing would work since an open neutral is not a complete circuit.
That’s a great idea though to shut off every breaker in the house except for that one, will try that tonight.
The neutral and ground are bonded in the main panel, so it is possible for the neutral to be open some where and the ground is being use for the return.
I’ll look at that more closely later but I just quickly tested the outlet before heading to work using a multimeter on the ohm/continuity setting and from neutral slot to ground slot there is continuity and very very low ohms, which leads me to believe they are bonded back at the source.
As @tmcqueen says, there can still be an open neutral and if they are bonded at the box. The hot leg will make 120 VAC with only the ground but that causes all kinds of problems. I have had open neutral problems in the past. Not saying this is one but its certainly worth the price of a plug in circuit tester to find out. Gremlins are always waiting in the wings for an opportunity.
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I chased a neutral problem with my tube amps a few years ago. My house is 70 years old and has been remodeled by the previous owner. The electrical is old and new, some outlets are grounded and some aren’t. The gizmo checker is the ticket to quickly check the outlets.
I will definitely check that, I’m not ruling anything out. I know the electrical is done properly though, I ran the circuit myself and recently changed my panel. I know my earth connection is properly bonded to the neutral at my panel but I won’t rule out any mistakes on my part.
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The ground and neutral should be bonded only at the main panel. Some knob and tube wiring from older buildings do not have a ground and if you tie the ground and neutral together at the outlet to use the newer standard three prong outlets, you will get a lot of hum.
My stereo system has new 20 amp circuits with proper ground wires and I was getting intermediate hum and noise from a Bruce Moore tubed preamp no matter what I do. The preamp came from the factory with the ground not connected as standard. I opened the unit and connected the ground and the hum is still there. I believe it is in the circuit because my brother has the same preamp and he brought it over and it was the same problem with the noise. Now I have a solid state preamp and no more noise, dead quiet.
I forgot to mention the Bruce Moore was also noisy in my brother’s system as well, but not as bad as my system. Sometime I can hear a radio station on the background as well. But with my new preamp, not a peep of noise.
Grabbed a greenlee plug tester. Everything lights up indicating the circuit is good.
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This is getting really frustrating but I think it’s pretty much narrowed down.
I started testing with every single breaker off in my house except for the single dedicated circuit. Everything was plugged into a simple power bar. No cheater plugs used.
I left the bhk 300’s in and connected them to two other preamps. 1 active and 1 passive. Hum with both, Just like with the BHK pre.
Next I decided to hook up the bhk pre to some DIY ncore 400 monoblocks I made years ago. No hum when everything is connected, interesting. Power everything on, and I was a bit shocked at the result. It was actually really quiet. The ncores are dead silent so all I was hearing was the preamp.
There was only 1 problem though, the left channel had some odd fluttering noise that I mentioned above. Right channel is dead quiet. Just that smooth consistent white noise when ear is near the tweeter.
I swapped tubes in the preamp but that doesn’t change that staticy flutter sound. Swap IC at preamp output and noise moves to the right speakers, so that sound is coming from the left output jack.
So from what I can tell, the ground loop issue is being cause by the amplifiers and the preamp has some weird noise on the left channel output.
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You have done a lot of police work and must be rightfully disapointed. Sounds like one channel in the pre needs a doctor. Just for shiggs does the HP amp make the same left channel noise?
Sorry, what do you mean by HP? I’m confused by that acronym.
Sorry for the abbreviation. HeadPhone 
Haha can’t believe I didn’t catch that. I will try that out , that’s a good idea.
The noise from the amps though is still very worrisome
Yes indeed. I don’t have any more ideas to offer. This stuff can sure be temperamental. My system was glitchy today so I decided to power everything off and boot it all back up again. When everything was back up and running I had no output at all. Turns out my EtherRegen switch forgot how to relay a signal. After pulling the plug on it and powering it up again everything was working. Sometimes I think having a plain ole Denon receiver and nothing else might just be OK.
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Just as a last resort, you don’t happen to know someone with a Shunyata Alpha NR or Sigma NR power cable to try on the 300’s (or just one of them)?
Also it might be the power distribution strip too if it has any safety features built in.