As all competent DC blockers have, there is a full wave rectifier on both the positive and neutral feeds. These will cause about a 2V drop in the AC voltage to the power transformer due to the forward voltage drop across the diode bridges. Its no big deal.
The Emotiva also has an RF filter consisting of a couple of inductors in series and caps across the line which might cause a little more voltage drop at high current. I don't know what these inductors are rated for, but the unit overall is pretty solidly built, obviously designed to sell at a higher price (extruded aluminum chassis).
Interestingly, the effective blocking capabilities of the various ones we have tried (PS Audio Humbuster, Emotiva CMX-2, and our much simpler unit (two diode bridges and a single 0.47uf 630V "safety cap" across the line after the diodes) varies substantially depending upon the AC source used.
At my shop, when everything is attached to a AC strip I normally use that has a ground fault interrupter built in, using the hair dryer at half power test, and an old Dyna ST-120 with its single ended iron transformer as a test subject, the hair dryer makes its transformer almost leap off the shelf with huge vibrations.
Our simple prototype DC blocker stops the vibrations completely. Neither the PS Audio or Emovita units are as effective. They tame the transformer buzz, but neither eliminate it.
Changing to a separate 20 amp dedicated line, all three units stop the hum completely.
At my engineer Dan's home lab neither the PS Audio or the Emovita units are effective, but our simple blocker is.
My electrical supply is typical suburban buried underground AC. Dan's supply is from a rural cooperative. We have no idea what is "different" from our electrical supply that Dan's. All are properly wired and grounded to code and the AC outlets are properly wired.
Anyone out there have any suggestions as to what could be different between Dan's electricity and mine?
Both the PS Audio and Emovita have lots of capacitors in their circuits. At Dan's lab, working with a PS Audio reverse engineered unit, he found that the ability to remove a DC spike IMPROVED as more of the capacitors were removed, with best results by far the very simple configuration we finally settled on to build into our Fet Valve amplifiers. This keeps our toroid transformers silent under all test conditions we have tried.
Regards, and open to suggestions.
Frank Van Alstine
