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Help I think my AC is polluted

After months of trouble shooting, I've come to the conclusion that my AC is the culprit of a very annoying hum. The thing that's odd is it only occurs every couple weeks, and only for two or three days at a time. The other thing that's strange is it happens on the weekend and ends usually by Monday night.

Let me give a few details about my system.
- I recently installed two dedicated 20 amp lines. This did not change the intermittent hum.
- I've tried cheater plugs during the hum and they had no effect.
- I'm in the process of auditioning two power conditioners. The Equi=tech Son of Q Jr. and the Furutech e-PT609. Niether of them has had any effect on the hum when it's happening.

I've put my ear right next to each component during the hum and found the Equi=tech transformer humming. I turned off all other components and the Equi=tech continued to hum, even in standby. When the hum is gone, the Equi=tech is dead quite. The hum doesn't change whether the powercords are plugged into the wall or either power conditioner.

I'm going to give the power company a call but I don't expect much help from them. I may try putting in an isolated ground and see if that helps. According to Equi=tech, balanced power should take care of most all ground loop issues, so I don't think an isolated ground will help much with this problem.

Has anyone else ever experienced this? Any ideas on a solution?

mootsdude

Showing 2 responses by stilljd

stilljd
155 posts
 
I have had similar experiences that occur when line voltage is low. I have 2 Arcam amplifiers and came home one day after dark around Christmas when all the houses were lit up with Christmas lights. Both of the amplifiers transformers were humming loudly. Scared the heck out of me. Unplugged the equipment and hooked it back up the next day. No hum in the transformers, everything fine. Later in the day when all the Christmas lights started coming on, back came the transformer hum.

Talked to the local dealer who sold me the amps and they had experienced the low line voltage problem when they first opened. After some research they had isolated the low line voltage and were able to make the local power company adjust the transformer feeding their shop. In our area (Cincinnati) the power company has responsibility to maintain a minimum working line voltage.

In my neighborhood the power transformer that feeds our house blew up shortly after that, and I never got to confirm the low voltage with meter readings or to request the power company check the voltage. I haven't experienced the transformer hum problem again with the replacement by the power company.

Not sure it is the same issue you are having, but just something I had experience with.

Jim S.
stilljd
155 posts
 
All,

Thanks for the discussion and information. It points out a misunderstanding I had about causes of transformers humming - not low voltage - but DC offset voltage (see stilljd above, I started the low voltage stuff). Now I have to understand what DC offset voltage is.

Also explains why my Alpha 9's CDP transformer hummed occasionally at home but not at work.

Appreciate the information and I didn't mean to post erroneous info, just hoping to learn more myself. My apologies.

Best Regards,
Jim S.
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