Reddit mentions of InstallGear Ground Loop Isolator Amp Noise Filter

Analog is the cheapest, fastest, and easiest.

Get a 3.5mm to RCA (stereo) Y adapter in the length you need:

https://www.amazon.com/Cable-iXCC-Shielded-Gold-Plated-Stereo/dp/B019D048XC/

Problem is, you may get buzzing from poor grounding, in which case you'll need to "lift" (isolate) the ground loop -

Plug something like this in-line, after the Y adapter, before the stereo AUX RCA inputs -

https://www.amazon.com/InstallGear-Ground-Isolator-Noise-Filter/dp/B077Y5DLBB/

or a newer type (plug this into the computer first, then that Y adapter):

https://www.amazon.com/REIIE-Ground-Isolator-Bluetooth-System/dp/B01JUOWB2Q/

Just read through your post again and a few more things came to mind:

All Deepminds have balanced outputs - make sure you are using a proper 3-conductor (TRS->XLR) cable to connect to your UMC

Check your gain-staging. you want to make sure your source signal is nice and high so you aren't raising the noise floor by amplifying it at your interface so your deepmind ought to be turned up quite high and your UMC should not have the gains cranked if possible. Even if you have some bus noise, proper gain staging can sometimes reduce it to the point where you can barely perceive it.

You mention that the noise changes with keyboard action which is a sure-fire indication it's bus noise from your computer. Try connecting your UMC to different usb ports to see if there is a difference. On my setup the high speed (blue) usb ports seem to be isolated better than the others.

Make sure your phantom power (+48v) on the UMC is turned off)

Check the USB cable that you are using to connect your UMC to the computer: some cables have a ferrite core, otherwise know as a ferrite bead or "choke" that looks like a little cylinder on the cable: https://en.wikipedia.org/wiki/Ferrite_bead This is meant to keep high frequency noise from messing up the USB signal and it shouldn't effect any of the frequencies that are in the audible range but just in case it's encouraging the ground to go one way or the other try a cable both with and without to see if it helps.

The MicroHD will most likely solve the problem but so will these for a lower price:

https://www.amazon.com/InstallGear-Ground-Isolator-Noise-Filter/dp/B077Y5DLBB/ref=sr_1_6?crid=KUPCV1LLYM77

https://www.ebay.com/itm/HKATOPS-3-5mm-RCA-Ground-Loop-Isolator-AudioStereo-Hum-Noise-Filter-Audio-W27/202731548848

*note that when using these you will no longer have a balanced signal so keep your cable runs short, and you will have to get RCA->TRS adaptors to connect it between your synth and your interface.

Transformer isolators take an unbalanced signal in one side and induce the same signal into the output without any physical connection between the wires - so you immediately get rid of any DC bias and the system has to find a different route to ground (usually through the chassis or the ground pin on your power supply as it was intended)

If, down the line, you want to get a real swiss-army-knife isolator box I suggest:

https://www.ebay.com/itm/Mackie-MDB-2P-Stereo-Passive-Direct-Box-DI-Box/392059765174

...or something similar. A good passive DI will let you attenuate the signal and lift the ground so you can use them to solve a lot of different issues.

Yep i think that’s what i’m going to get. Was recommended a ground loop isolator

(https://www.amazon.com/dp/B077Y5DLBB/ref=cm_sw_r_cp_awdb_t1_5HazCbG8DWADK)

If that fails i found this - https://www.amazon.co.uk/dp/B01BYIP4IE/ref=cm_sw_r_cp_api_i_lKazCbDZ83MYT

Do you think that could solve the issues as that has two balanced TRS outputs.

Just a lot to spend on something that might not solve my problem

Update 2: I have found the cause of the problem and what was needed to fix. I will post below what i found so if anyone else gets this, they can fix it.

https://www.youtube.com/watch?v=wnN31snqR9o
Everything needed to fix this in this video. It was a grounding problem caused by a crappy PC. This little box eliminated all static noises, and has actually increased audio quality. With this i also bought a 2x1/4" jack to RCA cable, as that is the type of input my monitors take, all equipment used listed here: (UK Amazon)
Ground Loop Isolator: https://www.amazon.co.uk/AV-Link-Ground-Loop-Isolator/dp/B000NVWB9O/ref=sr_1_1?ie=UTF8&qid=1522861082&sr=8-1&keywords=ground+loop&dpID=413Ja6ofpeL&preST=_SX300_QL70_&dpSrc=srch
2x1/4" Jack to RCA: https://www.amazon.co.uk/dp/B006H0E4YA/ref=psdc_407727031_t2_B004EBKV1Y
(Amazon.com products):
Ground Loop Isolator: https://www.amazon.com/InstallGear-Ground-Isolator-Noise-Filter/dp/B077Y5DLBB/ref=sr_1_2?ie=UTF8&qid=1522861210&sr=8-2&keywords=ground+loop+isolator
2x1/4" Jack to RCA: https://www.amazon.com/dp/B000068O19/ref=psdc_3236443011_t1_B004NCYVY2