Hey Nick,

Richard, I wasn't aware of a previous thread about the bass amp having it's own di...I'd forgotten all about that. With a di ahead of the amp you're getting the sound of the bass itself w/no eq other than the tone/volume pots. I used to have a bass amp w/a built in low-z out. After a couple of gigs ended up getting a Whirlwind di as it seemd the 'preamp sound' was more difficult to mix.

Here's my basic bass rig:
76 Gibson Grabber w/reverse p-bass pickup configuration(the E-A string pickup is towards the bridge, giving a little more 'punch' to the low end) It's not stock. Came w/a sliding p.u.
Peavey B112 50w bass amp w/4 eq pots, pre and master volumes.
Whirlwind EDB1 direct box.
Boss GEB-7 bass eq.
Boss inline bass tuner...can't think of the model #.(I use the Boss transformers for the eq and tuner as I've found batteries to be unreliable...though I keep a couple just in case)

When setting up I run the bass onboard tone/volume pots both wide open. Tone all the way towards treble. Bass to the tuner. Tuner to the direct box. Direct box to the eq, eq to the amp. All 1/4" patch cords. I set the master volume on the amp wide open/back an eighth of a turn. The pre-amp is on 2 or 3. I control the overall volume with the eq. The amp eqs are straight up. I run a 25' mic cable from the direct box to the pa channel. I use the tuner as a 'kill switch' during breaks.

This is the rig I've been using for about 15 years in a variety of acoustic or electic settings including, bluegrass, honky-tonk, swing, Irish/Celtic(my personal favorite) and backing singer-songwriters.

Nick, I hope any or all of this is helpful to your situation, but Richard is right on w/the technical info re the pa system...it would be to your advantage to print out this thread and keep it in a 3-ring binder. I know I'm going to. Hope your gig goes well.   Jeff