Homeplug noise in speakers

[Benedict]

Hi, I've bought a handmade stereo amp from my friend a while ago, and it's a decent amp. However it wasn't designed to filter out the emi coming from homeplugs (ethernet over powerline, from around 500k to 80 mhz signals). At the same time, I need a simple UPS to power my router and switch, things are next to each other and really impossible to move around. I also need to protect those devices from overvoltages. So my question is, what's better:

a) get a line interactive ups? not sure how well their filters work, if at all.
b) build a diy online ups with all the protection / filters?
c) build/get a filter, get some cheap standby/line ups, and make a small box with overvoltage and filters in it to protect the whole thing?
d) something else entirely?

bonus question (lel):
speakers get the 50hz hum too. nothing terrible, but still audible when nothing is playing. Any solutions to that perhaps? Installing a 49-51 Hz filter after the psu part? I'd probably need to check what's going on cause i had no ideas ripples can go past linear regulator chips. It's possible he didn't even put one inside even? Sigh

[macboy]

If you get 50 Hz hum, this indicates poor grounding in the amp itself. You may be able to improve this, but getting it right can be tricky if you have no experience in such things (as evidenced by your friend not getting it right).

[Benedict]

If you get 50 Hz hum, this indicates poor grounding in the amp itself. You may be able to improve this, but getting it right can be tricky if you have no experience in such things (as evidenced by your friend not getting it right).

Well, this will at least put me on the right track. Thx. Any ideas about the other question?

[macboy]

If you get 50 Hz hum, this indicates poor grounding in the amp itself. You may be able to improve this, but getting it right can be tricky if you have no experience in such things (as evidenced by your friend not getting it right).

Well, this will at least put me on the right track. Thx. Any ideas about the other question?

I would start with a snap on ferrite or two on the power cord and maybe even on the interconnects. Then i would move on to an appropriately sized filtered IEC socket. That means do not use a 15A socket if the amp will only draw 3A, since it won't filter as well as a 3A one. You could also add some capacitance across the line ... Use only X2 rated safety capacitors.

[Benedict]

Excellent. Thank you. Cheers. We need a beer smiley. 

[Zero999]

We may be able to provide more advice if you post a schematic. Ask your friend or try reverse engineering it.

Could it be a ground loop? What is connected to the inputs?

Are you using properly screened cable for the input signals?

Have you tried running it off a battery or bench top power supply?

[Benedict]

You're correct. I'll tinker around for now, but if it ends up being some silly ground loop issue, I'll get the schematic, pics, and post it here. Thx for the good will.