This converter works with both analog video and audio input and outputs SDI with embedded audio.
Please keep in mind that your source is 3/4" U-Matic and you will likely also need a time base corrector in the signal path between the output of the 3/4" VTR and the input of the HD10AVA Mini Converter; AJA does not offer timebase correctors, but you can find them from companies like Datavideo, Hotronic,TV One, etc. So your likely signal path would be: composite analog video output to timebase corrector, composite output of timebase corrector to HD10AVA Mini Converter, SDI out of HD10AVA Mini Converter to SDI input of the AJA Io Express. The analog audio out of the VTR can be routed to the HD10AVA Mini Converter, but you will need to check to see if the VTR is outputting professional or consumer levels (that model uses RCA audio outputs as opposed to XLR connectors and therefore may be outputting a consumer level); if so the HD10AVA can be configured for consumer audio levels via dip switch number four on the unit. Another thing to consider is if the timebase corrector introduces processing delay, you may need to route audio as well as video through the timebase corrector before connecting audio to the HD10AVA converter for optimal A/V sync.