Uh and that is supposed to achieve what exactly?
The diyadio.com forum post seems to be a load of rubbish by folks who don't have an idea about electricity (is that an audiophile forum, by chance?). I think that this gem sums it up pretty well:
Best way to get rid of DC on the trafo is to use an isolation transformer.
The "dc-blocker" schematic shows a gizmo that I seriously hope is not meant to be mains powered! 6.3V rated elcos in series with mains???
Someone thinks that those two anti-parallel diodes are going to keep that safe?? That looks pretty lethal
(Not to mention that those diodes pass whatever comes in right through, minus the forward voltage of the diode, so it will produce a distorted sinewave if anything - possible EMI problems).
The last one is just a variant on the previous one - an excellent way to set your house on fire or worse, because those elcos are certainly
NOT designed to carry so much current, never mind their 35V rating. One bad contact or blown diode and KABOOM the whole contraptions goes. This is like a Darwin award candidate project.
If your amp is humming with 50/100Hz hum, you need to add/fix the filters on the
secondary side of the PSU!