Transformers humimg........again

A balanced transformer does not seem to sort the problem of DC on the line although it does have advantages.

There is a simple circuit consisting of a bridge rectifier and four electrolytic capacitors (bypassing the rectifiers in the bridge in reverse bias mode) that can block DC. They are effective enough and cheap enough that they are often included in equipment to help prevent the noisy transformer issue.

http://www.diyaudio.com/forums/solid-state/2080-dc-filter-16.html
Scroll down to post 159.

They can also be inserted in the AC line although this should be done by a qualified technician. The circuit is compact enough that it can be installed in an electrical junction box.

Hi Shawn,
First off, you should know that transformers in NAIM gear tend to hum.
My Superline top line phono stage powered by HiCap DR power supply hums. Not all the time. When I have and can measure residual DC on the line. Also, when any dimmers are used in the house. My original Nait5's transformer also hums. I am not sure as to what extend Naim audio specs their transformers for core saturation but this is another element that triggers it at times. They are very high tech audio grade custom transformers and sometimes that is a drawback in  real world conditions. NAIM has always been an idiosyncratic company producing product as so. Much better after the passing of Julian Vereker the founder, CEO, and past designer. 
I hope this helps. Good luck with everything.

PS: You can also contact Chris West (ex-service manager at NAIM UK) at AV Options in IL (the only factory trained and authorized service center in US).

Best,

Puiu

High core saturation  margin I meant.

atmasphere
What is your line voltage? It should not exceed 125V for more than a second. If its high that could explain the problem.

+1 for checking this.

Canada is supposed to be 120v.
In Australia we’re supposed to be 230v mine measured quite constantly around 250v, incandescent light globes would last a couple of months, yes my transformers were a little noisy with a screwdriver to the ear test, but the worst is your paying more for your power, when using unregulated appliances, fridges, aircon, heaters,lighting, poweramps, microwaves ect ect.
I complained very hard, and eventually they put the whole street on a different tap on the pole transformer down the road. Now I have correct 230- 235v no more globes blowing, and my usage is down. And I swear my system sounds better, even after I re-biased my amps, back to what they were with the 250v.

Cheers George

You can put in a large isolation transformer and create your own neutral.  It is called a "separately derived system" in the NEC handbook.  I designed a 50 KVA split phase line system, 120V-0V-120V, from 3 phase 208VAC using two 25KVA isolation transformers for a solar energy lab here in CA.  This is the basic 120V/240V mains in North America.  You will also need a suitable earth ground on the output neutral.  For your system, a 10 to 12KVA isolation transformer will do, such as a Square D or equivalent.  Do get a good one, the cheaper ones have very little headroom.

The hum in my I have found in my system deals with the transformer magnetic field driving into the chassis and creating a leakage current flowing to the earth ground wire or through the RCA shields.   I don't recommend isolating your equipment from earth but you can isolate your transformers in your equipment from the chassis using grommets.  To test this theory, remove all connecting cables and plug the unit into the mains, then turn it on, and see if you have hum.  If the unit does not hum and if it does not have a earth ground in the power cord, connect the chassis to earth and see if it starts to hum.  If it does, you have found part of your problem.   Do this for each piece of equipment that plugs into the wall.

Also, I did have one obscure hum problem once but it was the receptacle where line and neutral were swapped.  I had hum every time I plugged something into this outlet.  Given what you published, I assume this is not your problem.   You can get a outlet wire checker at your local hardware store for 10 bucks or less - it will save you from opening up each outlet to check the wiring.