2. amps-preamps
  3. 149155-45034

power grid issues?

Hi  Agoners. By chance, are there any bright EE around who may have an answer to this? I get "grid hum" on my Balanced Audio Technology tube amp. It is irregular, happens for different intervals and different lengths of time. I have check my house system by shutting evert appliance of during these "hum intervals" and I do know it is not my house systems that are creating this noise, or fluctuation. I had PG&E check their system. They used a neutral detector and said that their neutral to the source is good. The power is stable. This morning the hum, which is audible in the transformer, was a wave. on off on off on off, for a good hour. then it stopped. Yesterday it was just a straight hum for a period of time. no fluctuations at all. What is going on? 
Thanks for any input!
Greg
greg22lz
greg22lz OP
182 posts
 
interesting comments. There isn't anything connected to my pre-amp except CD and amp. No other external sources. The circuit is an isolated circuit. Stereo only. 
Erik, you say that the emotiva reduces your transformer hum. It doesn't eliminate it? My next step in evaluation is to shut off all breakers to see if it is emanating from some DC source in the home, which at this point i doubt.
Thank you for the comments ! I will keep you posted as to the results!
Greg
erik_squires
16,056 posts
 
@theaudiotweak is confusing ground loop issues with DC.

Ground loop issues cause hum out the speakers, and digital jitter which may or may not be audible. 
Mechanical humming from transformers is not caused by this.

Best,
E
greg22lz OP
182 posts
 
@erik_squires yes, I figured that out!
Post removed 
jea48
4,425 posts
 
greg22lz OP

180 posts
05-31-2019 11:22am


the hum i am referring to is my transformer on my tube amp. PG&E has assigned an EMF specialist to help determine where the noise is generated. I do not believe at this time that it is generated from my house due to its irregular intervals, i.e., time of day, inability to duplicate it when it is not there, everything turned off in my house. Yesterday it was a constant hum for at least and hour this morning it was an oscillating hum for about an hour. I am on the same line as my neighbor. We are the only two houses connected to the transformer across the street. They have solar panels that run off of AC. I took my amp and plugged it into different circuits in my house and got the same hum. Maybe I should go to my neighbors house and plug it in to find out if it would hum over there.

Maybe I should go to my neighbors house and plug it in to find out if it would hum over there.

Yes you should!

There is a very good chance your neighbor’s solar system is causing DC offset on the AC power mains in your home. It may also be causing the utility power company’s power transformer to run hotter than it normally would, therein shortening it’s life.

Found this doing a quick Google search.
https://www.researchgate.net/post/What_are_reasons_of_dc_offset_current_in_grid_connected_inverter


PG&E has assigned an EMF specialist to help determine where the noise is generated.
They will have testing equipment that will identify possible harmonic distortion that your neighbor's solar system may be back feeding onto the power company’s AC power system.

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