Is it possible to use a SansAmp Bass Driver DI just as a DI and not have it change your tone? I currently use it for better tone with my small rig but I have been having issues with my DI jack in my big Ampeg Classic amp at some venues. If they don't have a DI box for me to use can I use the SansAmp the same as a DI box?
The Bass Driver DI utilizes a high quality buffer and if anything should help preserve your tone into your amp and to the board. You didn't mention if you have a passive or active bass. If you have a passive instrument and use a passive DI, many times the input impedance of those boxes is too low for a passive instrument and will load down your signal. Hopefully if you are at a venue the sound person will provide the appropriate DI.
The original intention with the Bass Driver DI was to plug into the unit and send the "parallel" output to your bass amp and use that as you normally would for your stage sound and monitor. You would send the effected SansAmp XLR output to the PA to give you the sound of a mic'd tube amp. You should explore that option unless you just want the sound of your bass guitars pickups coming through the system.
The DI's on most amps are fine but in general don't have a frequency compensated output. That's cool if you play clean but if you use distortion it's nice to have a speaker sim to warm up the tone. If you're using a full range bass cab and like that tone it probably isn't a big issue.