Dead spot caused by AMP?

I recently bought a new bass and I have been very satisfied by using it for recording in my studio and low to medium volume playing in my home.

Nice even sound & zero "dead spots".

Yesterday I took it to band practice and the craziest thing happened when I plugged into a battered PV TNT amp the studio had for band use.

All notes were sounding great w/ the exception of the G note (E string 3rd fret) that had at least a 30% volume drop!!

I've never heard of a dead spot under the low E string & especially that low!

The bass when played acoustically or through an amp in my home or when recorded (flat w/o comp or a pre amp) sounds great on the particular note w/o a dead spot.

Is it possible that this "dead spot" was caused by some strange interaction between the bass and the amp (or the room) ?I played very close to the amp almost facing it & at a high volume.

Yeah, I am wondering if it might be a frequency problem.
I would also check my pup heights.

Maybe a speaker problem?

That's a weird one, Nick!!!

Cheers, Tim

It's definitely not anything on the bass, since it's fine with other amps or recorded direct.

Keep in mind that a dead spot is nothing more than a frequency cancellation. The amp head isn't a likely suspect, but either the speaker cab or some interaction between the cab and the room is hitting the same frequency as that note -- either the note's fundamental or one of the lower overtones.

First thing I'd try would be to move the cab around.