Improving performance of Tigertronics SIGNALINK USB

I use SIGNALINK USB modem interface for digital modes on HF (mainly FT-8) and Meteor Scatter on VHF.  It is very handy because the volume of TX and RX can be adjusted by pots on the front panel, and it has a built-in VOX circuit - eliminating PTT keying through a serial port. And as I always connect up the transceiver  for DATA through the DATA ports on the back panel, the built-in VOX of the transceiver is not active (at least : with ICOM rigs).

What can be improved on this modem ? There are several things to do ...

Original audio passband

Several HAMS have done a wonderful and valuable job to improve the modem, e.g. Peter OZ1PIF - see and Matt AB8VJ.

I can only recommend the following modifications (download pdf summary, should above hyperlink not work), which proved to be very effective :

Passband with ETAL transformers

Good luck with the mods and CU in digital mode !