Preamp Noise with High-Efficiency Speakers

This thread has been quiet for some time but has yielded some well sorted out theories.
I stumbled on it with hopes of finding a solution to a hum problem that seems to center around a phono preamp and like others on here, brought to light by some high efficiency speakers.
I've tried a star grounding system, moving power/ICs, etc.
Have dedicated lines and sub panel, a Balanced Power Technologies 3.5 Sig Plus. After I installed the BPT, the edge I was hearing in the presentation took a step back, and yes, the presentation became more natural.
Along with it came the hum, which was previously more subdued.
I will spend some time this weekend chasing down possible sources, not looking forward to this.
Question is: could the Power conditioner's large transformer be reaching 3 feet or so to the phono pre?

Hello Dentdog,
I hope you soon find an answer to your system hum issue. I use the same BPT unit and it's terrific! I have no hum problems with its use un my system.

Hum is 60 or 120 Hz noise from the power, and there are two way to pick it up, either conducted or radiated.

Radiated powerline noise is when you have a high current device and it throws out a magnetic field. Any high impedance conductors (your line levels and phono lines) in the field will have an induced 60 or 120 Hz voltage picked up on their wires. You test for this by moving the high impedance wires around. If that causes any change, you have a radiated energy pickup problem. Knowing that, then you can do things like try to improve wire separation (the energy falls off as the inverse of the square of the distance, i.e. it falls off rapidly), or use shorter wires (less pickup area), or re-orient the wires to make them perpendicular to the radiating source (max pickup is when they are parallel to the radiating field).

This radiating magnetic field normally comes from the powerlines or from the power transformer in the high current devices like the final amp power supply.

Trying to shield lines from the 60 or 120 Hz magnetic fields is useless, because at that low frequency the magnetic field cuts through shielding materials very easily. Shielding only works to guard against high frequency pickup. Distance, wire length, and orientation are your best friends.

The other way to pick up hum is by a conducted path. The 60 or 120 Hz noise is traveling through the conductors and getting back onto the input source. If the test above for radiated pickup doesn't work, then you should try electrical isolation methods such as messing with power routing (star or independent outlets) or putting a noise suppressor/filter on the phono power.

Divide and conquer... find out which of the two problems you have first, so you narrow down the type of action you need to take.

Hi Charles1,
As with most things audio the devil is in the details. The BPT certainly does a lot of things favorably, a sense of ease permeates the music now and is very pleasing. Will have to don my Sherlock hat although Inspector Gadget is a more appropriate. I'll get it, and along with the solution a bit of education.

Dentdog,
You were certainly given very solid feedback from Tom32. I believe you'll get this problem solved.