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Thanks again mm, appreciate the extra brain cycles you are putting into this for me
Haven't had much of a chance to fiddle around yet due to life/wife/work etc, however...
Tired of looking for a 'cheater pulg' or earth lift, I made one with a double adapter and a pair of pliers heh... Broke off the earth prong. Using this on the amp solves the problem. Wont leave it there as it's dangerous. Doesn't make a difference on the TV or PC. Tried the desktop with the corsair PSU, still hums. No dust in the amp.
Found this site which was very interesting. Also has interesting reading on cable 'snake oil' merchants. In the conclusion part it talks about switched mode PSUs ie PC PSUs not really being grounded, in fact devices with SMPS's chassis 'float' at around 50% of line in current if I read it correctly. Not sure why this doesn't cause instadeath whenever I touch my PC, but I will never ever remove/insert the signal cable with the amp or pc on.... If this was the case, I would have thought EVERYONE with an HTPC and analogue signal leads would have issues, but search hits are rare.
One other interesting thing I found out which is why I got confused in my first post... I get a loop (hum) via the audio interconnect between the PC and Amp when the amp and PC are earthed through the same wall plug and nothing else is plugged in. If I unplug the PC from the wall, hum is gone, but if I then plug the VGA lead to the TV into the PC and the TV is earthed, hum returns.
As in my first post I tried connecting the chassis of my amp and PC together with some hook up wire. Was fairly light gauge and only made the problem worse, introducing lots of digital noise to the hum. I forgot about electrons being lazy, so will try this again with some heavy cable from my old car audio set up, will also ensure sound card has an extra ground from mounting plate to chassis. I will remove the VGA lead to the TV when I do this (cant remember if I did last time). Am going to muck around with different locations for this grounding wire as well, next to PC PSU, straight off sound card plate etc. My amp already has a grounding point for a turntable, so can assume this is good to use. Was also wondering if I grounded one of the line in RCAs on the amp to earth if this would help.
All this mucking around with electrons does make me nervous as it involves 240V AC but I reckon as long as Im only touching the earth side of things I should be okay.
I had a chat with a mate last night who reckons most modern appliances (my TV, maybe PC) are earthed through neutral rather than ground. If this is the case, it could explain the porblem, but then why does my TV have a three pinned power plug?
Oh well, will keep fiddling on and update as results permit....

<blockquote data-quote="littlematt" data-source="post: 879355" data-attributes="member: 25302">Thanks again mm, appreciate the extra brain cycles you are putting into this for me <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite24" alt="(y)" title="Thumbs Up&nbsp; &nbsp; (y)" loading="lazy" data-shortname="(y)" />Haven't had much of a chance to fiddle around yet due to life/wife/work etc, however...Tired of looking for a 'cheater pulg' or earth lift, I made one with a double adapter and a pair of pliers heh... Broke off the earth prong. Using this on the amp solves the problem. Wont leave it there as it's dangerous. Doesn't make a difference on the TV or PC. Tried the desktop with the corsair PSU, still hums. No dust in the amp.Found<a href="http://sound.westhost.com/earthing.htm" target="_blank"> this</a> site which was very interesting. Also has interesting reading on cable 'snake oil' merchants. In the conclusion part it talks about switched mode PSUs ie PC PSUs not really being grounded, in fact devices with SMPS's chassis 'float' at around 50% of line in current if I read it correctly. Not sure why this doesn't cause instadeath whenever I touch my PC, but I will never ever remove/insert the signal cable with the amp or pc on.... If this was the case, I would have thought EVERYONE with an HTPC and analogue signal leads would have issues, but search hits are rare. One other interesting thing I found out which is why I got confused in my first post... I get a loop (hum) via the audio interconnect between the PC and Amp when the amp and PC are earthed through the same wall plug and nothing else is plugged in. If I unplug the PC from the wall, hum is gone, but if I then plug the VGA lead to the TV into the PC and the TV is earthed, hum returns.As in my first post I tried connecting the chassis of my amp and PC together with some hook up wire. Was fairly light gauge and only made the problem worse, introducing lots of digital noise to the hum. I forgot about electrons being lazy, so will try this again with some heavy cable from my old car audio set up, will also ensure sound card has an extra ground from mounting plate to chassis. I will remove the VGA lead to the TV when I do this (cant remember if I did last time). Am going to muck around with different locations for this grounding wire as well, next to PC PSU, straight off sound card plate etc. My amp already has a grounding point for a turntable, so can assume this is good to use. Was also wondering if I grounded one of the line in RCAs on the amp to earth if this would help.All this mucking around with electrons does make me nervous as it involves 240V AC but I reckon as long as Im only touching the earth side of things I should be okay.I had a chat with a mate last night who reckons most modern appliances (my TV, maybe PC) are earthed through neutral rather than ground. If this is the case, it could explain the porblem, but then why does my TV have a three pinned power plug?Oh well, will keep fiddling on and update as results permit....<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite5" alt=":confused:" title="Confused&nbsp; &nbsp; :confused:" loading="lazy" data-shortname=":confused:" /></blockquote>

[QUOTE="littlematt, post: 879355, member: 25302"] Thanks again mm, appreciate the extra brain cycles you are putting into this for me (y) Haven't had much of a chance to fiddle around yet due to life/wife/work etc, however... Tired of looking for a 'cheater pulg' or earth lift, I made one with a double adapter and a pair of pliers heh... Broke off the earth prong. Using this on the amp solves the problem. Wont leave it there as it's dangerous. Doesn't make a difference on the TV or PC. Tried the desktop with the corsair PSU, still hums. No dust in the amp. Found[URL='http://sound.westhost.com/earthing.htm'] this[/URL] site which was very interesting. Also has interesting reading on cable 'snake oil' merchants. In the conclusion part it talks about switched mode PSUs ie PC PSUs not really being grounded, in fact devices with SMPS's chassis 'float' at around 50% of line in current if I read it correctly. Not sure why this doesn't cause instadeath whenever I touch my PC, but I will never ever remove/insert the signal cable with the amp or pc on.... If this was the case, I would have thought EVERYONE with an HTPC and analogue signal leads would have issues, but search hits are rare. One other interesting thing I found out which is why I got confused in my first post... I get a loop (hum) via the audio interconnect between the PC and Amp when the amp and PC are earthed through the same wall plug and nothing else is plugged in. If I unplug the PC from the wall, hum is gone, but if I then plug the VGA lead to the TV into the PC and the TV is earthed, hum returns. As in my first post I tried connecting the chassis of my amp and PC together with some hook up wire. Was fairly light gauge and only made the problem worse, introducing lots of digital noise to the hum. I forgot about electrons being lazy, so will try this again with some heavy cable from my old car audio set up, will also ensure sound card has an extra ground from mounting plate to chassis. I will remove the VGA lead to the TV when I do this (cant remember if I did last time). Am going to muck around with different locations for this grounding wire as well, next to PC PSU, straight off sound card plate etc. My amp already has a grounding point for a turntable, so can assume this is good to use. Was also wondering if I grounded one of the line in RCAs on the amp to earth if this would help. All this mucking around with electrons does make me nervous as it involves 240V AC but I reckon as long as Im only touching the earth side of things I should be okay. I had a chat with a mate last night who reckons most modern appliances (my TV, maybe PC) are earthed through neutral rather than ground. If this is the case, it could explain the porblem, but then why does my TV have a three pinned power plug? Oh well, will keep fiddling on and update as results permit....:confused: [/QUOTE]