HA Mode latency

Can someone explain to me how HA mode works.
What I’m trying to do is route the inputs to the line outputs.
I tried this on my UR-RT4 e.g.: Input 1 routed to Line out 1 , Input 4 to Line out 4. The line outs fed into a mixer . This was for a live recording interfacing with an in house P.A. that no sends available.
The only issue I came across was there was some latency. No effects or processing , just dry signal in and out.
I have 2 UR816C interfaces. If I use them in HA mode, will I be able to run 8 inputs to 8 outputs without latency.

What is HA?

It’s a mode that allows 2 UR816C interfaces to work together, just not sure on the intricacies of how it works

I think your expectations are wrong.
HA mode on the UR816C sends the inputs to the ADAT outputs with no other routing possibility.
The 8 preamps work as input extension only, and the ADAT input is routed to the available line outs.Remember to connect the word clock.

As far as I know, the UR-RT4 doesn’t support the HA mode.

I guess the HA means head amp.