[Dr_C2]

That’s great news, thanks Flat4 for sorting this.

To summarise based on our collective findings:

There are several versions of the DSD TECH  SH-U11.

The F version manual says ‘use the jumper if needed’, since this is to reduce signal reflections relating to impedance mismatch I included the jumper - and it works perfectly.

The H version manual says ‘don’t use the jumper for short cable lengths’. By not using the jumper you found it works correctly. Thanks for this Flat4.

All now clear until future revisions arrive!

Meanwhile I hope you enjoy very good PC-to-APB comms with the confidence there can be no ground loops or signal noise spikes between the PC and the APB :)

c

[flat4]

After hours of more intensive testing, thanks to firends joining me yesterday, I can report that this solution went smooth, and is, at least, as reliable as the old cable solution. I also appreciate that there are some LEDs showing com status, as sometimes my APB encounters some weird freezes, and that these LEDS helps to understand what's going on.

Many thanks to Dr_C for sharing this solution.