Can someone edumacate me on DI boxes?

Nope, a DI is not necessary if you're just plugging your bass into an amp. The amp is designed to interface directly with the bass.

 

Though there are some DI pedals that can also be used to flavor your tone, even if you run straight to your amp, such as the Tech21 Sans Amp or (Im pretty sure) the MXR M80

 

In a live performance context, a DI is used to send a signal to the front-of-house and monitor engineers to be amplified by the PA. While micing your amplifier also can accomplish this, it has become standard procedure to rely more heavily on a DI instead. Additionally, a whole other dimension of sound is possible when DI's and amplifiers are used together properly.

Most professional players who use an amplifier also employ a DI when playing a venue with a significant PA. That DI may be built in to the amplifier, or a separate component used in conjunction with the amplifier. Some modern players prefer to skip an amp altogether & rely on a DI exclusively (while praying for a competent monitor engineer).

By the way, there is no wrong approach. DI w/ amp; DI vs. amp...

 

A DI is not necessary unless you want to record or gig without miking your amp. The reason so many bassists discuss DIs is because most soundguys at gigs (and producers/engineers in the studio) don't want to mike bass amps, and insist on taking a direct signal from your bass. I personally hate it, but it is what it is.

 

At a minimum it's a good idea to have a DI (either a separate box or an output on the back of your amp) which you know is good -works reliably, sounds good, no noise, etc. ...Because you're going to need it one day. Your speakers may blow, or some part of the amp craps out, or you forget the speaker cable at home, or the venue has terrible boomy acoustics and they keep telling you to turn your amp down until you can't hear yourself over the drummer... That day you will be glad you had a reliable and good-sounding DI handy.

 

...and the DI goes at the end of your pedal path, with the XLR out going to the house and the 1/4inch out going into your amp (if you're using both) yes? Never owned a DI and have relied on others to set them up for me at gigs with PAs...

 

Yes, unless the soundman hates effects (and some do)- they will insist on taking the DI signal straight from the bass, with the 1/4" split then going into your pedals and thence to the amp. At that point it's a question of balancing your tonal desires against the will of the soundman.

 

Sorry to bring up an older thread, but I have a stupid question. Say that I like my fingerstyle tone on my amp, but it translates to a not-so-good slap tone. I'm thinking of getting an MXR M80 or Seymour-Duncan Paranormal to function as a slap EQ and as a DI. But here comes the stupid question... does the DI send everything to the FOH, even if I have not engaged the pedal, or does it only send a signal when I have pressed the footswitch? Once again, sorry... I'm a DI box noob, I've only used the DI on my amp up until now.

 

I've never used the specific pedals you are asking about, but in general a DI should always send its signal regardless of whether any additional tone controls, etc. that it might have are switched on or off.

Somewhat related: On many amps or preamps that have a built-in DI, you'll find a "Pre/Post EQ" switch that will determine whether your EQ/tone settings are applied to the sound coming out of the DI.