Let me try again…
First, I’m going to assume that you’re not getting shocked from touching any metal on any of your components.
Just to be sure, you can pick up an electrical outlet tester at the hardware store that will glow green ( or amber) if the outlet is wired properly and the ground is functioning as it should. I would also recommend you pick up 4 to 6 ground-lifts. (see below) they come in very handy in audio environments such as stage and studio.
Also, your DAW, Mixer and Amplifier ( and other connected equipment ) should all be plugged into the same electrical outlet using a good surge protector ( at least 1000 joules ) or better yet, an A/C line conditioner. I highly recommend Furman PL-PLUS C 15 Amp Power Conditioner. Amazon sells for $239.00
I can’t rave enough about it… read the reviews.
Anyway, back to your hum…
Always turn off your amplifier before plugging and unplugging power cords, Turn down the amplifier volume before plugging and unplugging audio cables.
Now, unplug the electrical cord of all equipment that is connected directly or indirectly to your mixing board. You will leave your power amp and Mixer still connected to the A/C power, but turned off.
With the mixer on and the Master faders on the Mixer pulled down, turn on the Amplifier and bring up the Volume controls on the Amp.
Do you have the Hum?
I would assume not, but let me know.
If you do have hum, you need to install a ground-lift on your Amplifier. a ground-lift plugs onto the end of the electrical cord and converts the 3-prong plug to a 2 prong. Let me know if that doesn’t clear the hum.
Btw, I have never had an issue with using ground-lifts where needed, as long as no one tries to defeat it’s polarity by reversing it in the outlet. NEVER, EVER do that, people!
If you have no hum, bring up the Master faders.
Do you have the hum, now?
If you have no hum, then the electrical connection between the Board and amplifier are functioning properly.
At this point I should tell you that there can be more than one piece of equipment that can contribute to this so it’s important to continue to check the rest of the equipment, but do so one at a time, and disconnect each one before testing the next.
And, there is no point in continuing if you have not cleared the hum on the previous equipment (the Mixer and the Amp).
So assuming we’re making progress, lets connect the power to the DAW (computer). REMEMBER: the Amplifier is powered OFF!
Master fader out of the DAW is pulled down. Mixing board is turned on next. Faders down. Next, turn on the Amplifier.
Amplifier Volume up.
Mixing board Master fader up.
DAW Master fader up.
How are we doing so far?
If you have a hum now, Power amp off, install aground lift on the DAW electrical cord.
By now, I hope you see the pattern were using.
Once the electrical has been straightened out, we can talk about noise coming from audio cables.
I’ll be happy to help you further if needed.
Let me know what’s happening and feel free to ask questions.