I’ve been using this 6ch preamp board

To regulate the volume of this 5.1 decoder

because the 5.1 decoder’s output needs pre amplification and the IR is randomly affected by the TV’s remote. I can use the TV’s variable analog output to control volume but of course only with analog input to decoder providing suto surround. Using optical I loose the tv control and as a result use the 6ch preamp for signal magnification and control.

The preamp serves it’s purpose well, no cross IR remote codes causing mischief, volume control, and adequate signal magnification. However it’s seemingly not a very well built unit. The usb-c power input broke off and required soldering and the subwoofer level adjustment jumps all over the place, the potentiometer dial isn’t super accurate as it is. Seller has nearly perfect rating but the repair would take forever and it still might be a fixed troublesome unit.

I’m looking at some other compact 6ch preamps that have a nicer display that better matches the decoders display. The two others I see both have what looks like jst connectors but with a common ground. If I were to give one of these a go, how would I wire it with only one ground spot? I’m really still quite green behind the ears with this end of the hobby and my only idea would be to splice the six outputs grounds into one wire going into that ground location. The reason I bought the original preamp was because the grounds were internally connected with a straightforward rca connection bank. I yanked the rca’s and added these phoenix connectors for simple 3 conductor wire connecting between the two boards and amplifiers.

Here’s one I'm looking at

[IMG align="left" alt="Lawnboy"]https://www.diyaudio.com/community/data/avatars/s/542/542821.jpg?1667862181[/IMG]

 

It's really not clear what you are trying to do.

But yes, if you are connecting audio sources, connect all the grounds together at the mixer/preamp input

 

I’m just wondering how to ground each channel cleanly. Just seems like there should be a better way than to wire nut the six grounds into one wire going into the one spot. On the 6ch preamp I have now, there’s an easily accessible ground for every two channels. For instance, I was able to solder three connector phoenix jacks where left and right shared a common ground.