Finally went and cleaned up this project. Posted a while back about 60hz hum and got lots of help but unfortunately not specific enough. Yes we knew it was a ground loop problem but how to solve it. Thought I would post the solution in case it helps anyone else. 
Basically in a nutshell...dont wire the ground scheme the way the f5 board is labelled. The f5 board has an input and ground, power +24v, -24v and ground and output and ground. My first wiring arrangement had the power ground going to ground on the ps board and the other two grounds leading to the barrel of the input rca and black output rca (both isolated from chassis). Slight but very noticeable hum on drivers when ear brought closer than 50cm to the drivers.
New solution: connect L input Rca ground to L black speaker out, do same on Rhs. Connect the two black speaker outs with a wire. Connect the centre of the wire going between black speaker outputs to the ground on the power supply. Connect the power grounds on each f5 board to the same ground point on the power supply that you just connected the input and output terminals to. DO NOT use the input and output ground points on the f5 boards. The f5 board should be connected to ground with only 1 cable.
Think this isnt big news to some of the old hands but wasnt that obvious to me. I was using recipe book approach i.e. connect everything labelled as labelled. Not connecting some of the labelled grounds wasnt immediately obvious as a newbie.
Just putting it out there if it can help any other newbie hummers as its flippin frustrating to be told "oh its a ground loop issue" without an exact instructions on something to try to resolve it. Hope it works for you if you need it.
Thanks again for the advice. Cheers!
Basically in a nutshell...dont wire the ground scheme the way the f5 board is labelled. The f5 board has an input and ground, power +24v, -24v and ground and output and ground. My first wiring arrangement had the power ground going to ground on the ps board and the other two grounds leading to the barrel of the input rca and black output rca (both isolated from chassis). Slight but very noticeable hum on drivers when ear brought closer than 50cm to the drivers.
New solution: connect L input Rca ground to L black speaker out, do same on Rhs. Connect the two black speaker outs with a wire. Connect the centre of the wire going between black speaker outputs to the ground on the power supply. Connect the power grounds on each f5 board to the same ground point on the power supply that you just connected the input and output terminals to. DO NOT use the input and output ground points on the f5 boards. The f5 board should be connected to ground with only 1 cable.
Think this isnt big news to some of the old hands but wasnt that obvious to me. I was using recipe book approach i.e. connect everything labelled as labelled. Not connecting some of the labelled grounds wasnt immediately obvious as a newbie.
Just putting it out there if it can help any other newbie hummers as its flippin frustrating to be told "oh its a ground loop issue" without an exact instructions on something to try to resolve it. Hope it works for you if you need it.
Thanks again for the advice. Cheers!
