Hello Mike,

I'm afraid that external ISDN modems are not suitable for audio links. They are fine for single channel and Internet access, but don't support sustained full rate two channel communication as is used by ISDN audio codecs.

On the AudioTX website there is a section that lists the tested and supported ISDN adapters - Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to or

Using a mic pre-amp will indeed improve the quality of your audio - mainly because it will allow you to use a professional balanced mic, which is something the standard soundblaster mic input does not support.  I don't think a mixer is necessary for a voiceover setup.

You can also opt to go for a professional audio card - these are not that expensive as they used to be ten years ago! With an AudioTX Communicator system the sound quality is mainly defined by your mic and the sound card. If the budget is tight then you can of course just stick with the soundblaster for now and replace it with a professional sound card at a later date, but I would try to get it in from the start as it is an important bit in the setup.

Best regards,

Edwin.