Mesa Analog Vs Step Dir

I know I’ve tuned my other machines.
I usually bench test first. Then install and tune, then connect Linuxcnc and tune it. And the trouble start when I connect the analog control.
Even with analog Control and the servos have no load they have 50hz vibration. Which I can’t get rid of. With the spindle I don’t have the issue the wires could be routed differently and I can use other better shielded wire. For the drives I can’t do this easily. I twisted and try to shield the wires with tape. But it didn’t improve. And have no idea what else to do. I could start to add ferrites or try to reroute all other cables and chasing down the issues. But I figured going digital would be quicker

50Hz vibrations are from interference or bad grounding/shielding or miss wiring, always.
Analog grounds are usually not connected to machine ground, but sometimes they are, something that can not be said for sure you should or should not do. It depends on a lot of things.
If you are sure the wiring and grounding is correct, use a 1KOhm resistor between analog ground and machine ground, if it does improve noticeably, use a 100 Ohm resistor then 10 OHm, and see if that helps. If the any of the resistors heat up or burn, stop, remove resistor and check wiring.
Do keep in mind, this is the last resort and not advisable at all, but i had to do this once on an older machine and all was good, but it might cause issues.

It wasn't clear you did tuning from you previous posts(or mu reading), sorry.

Diy shielding never works, twisted pair shielded cable is not that expensive and may be quicker solution.
...thinking now, how analogue signal running 20-30cm from mesa board to servo drive picks up all that noise anyway? Or??? did you install drives next to the motors and ran control cabling all over the machine?

I was kind of lazy and used a prewired dB 50 connector to wire up the drives. They are still in the switching cabinet. But I needed to open them up quite soon to wire in the connection to the limit withes. So then they run open for about 80 cm next to main power an most of the other three phase auxiliary power lines for lubrication, coolant, fans and so on.
I did solder the db 50 connectors for my lathe and used network cables there. But I hated it and needed some troubleshooting later due to mistakes i made. I was hoping to get away with it. But I didn’t. I could spent one night soldering up the cables and another fixing them.
The cables I have are fully connected, so converting to step dir is easy.
I could try solderfree connectors… but they would be more expensive than the additional mesa board I need. And I want to get the machine running before I have to move her to my new shop. I really don’t like these db50 connectors. My spindle driver is better at this point but it’s also much bigger.

@PCW may I ask if is there a ready to use bitfile for the 7i97 and 7i85s I just found some of the 7i85 and the Firmware download on the page 7i85s doesn't work for me.
Many thanks 

You have a 7I97, not a 7I97T?