Having trouble diagnosing rig issue

[Largedon]

Rig: Markbass F1 into a Epifani UL2 410 cab. (I also use a full pedal board and compressor but I know these aren't the problem.)

The problem I'm having is that during gigs I'm starting to get a distortion out of the tweeter after about 1.5-2 hours of usage. I've tried to recreate it at home and can't get it to do it, so I'm really having trouble diagnosing the problem.

It originally happened at a Halloween gig when I was playing a song that required using a pick (which I rarely use). I assumed that I had blown the tweeter, but when I hooked up the rig at home, it sounded great even at full volume so I didn't stress about it. Rig worked fine for the next few gigs and then its done it again at the last two gigs I've played. If I turn down the tweeter it goes away so it doesn't appear to be affecting the 10's.

I don't think its a blown tweeter because it would sound distorted all the time (or at least I would think so). Could it possibly be the crossover or other electronic in the cabinet. It's almost like once something gets hot it starts distorting. I was thinking that maybe the head was clipping too much and could possibly cause the problem, but last night I made sure the head didn't clip at all and it still happened.

The Markbass F1 appears to be working correctly, I don't believe it's the source of the issue but I guess anything is possible. The only issue I've head with the head is that the fan will whine a little bit when I first turn it on until it warms up and then it goes quiet. I'm assuming that the lubricant either gets too viscous when cold or there's not quite enough in there until its runs for a minute and lubes it up well. Not sure if this could be the problem but I've seen stranger stuff happen.

Thanks in advance for any help you can provide.

[Jim Carr]

Assorted questions: Do you have a back-up head and/or cab for testing? Are you using an active bass? You said the effects/pedals are not involved. Care to elaborate how you know? Have you called Epifani?

[dmusic148]

+1 to Jim's post. Also, yes, it's possible that the crossover is the culprit, but very, very unlikely.
Years ago I had a pedal tuner that developed a problem and created exactly the problem you describe. I mean Exactly.

[Largedon]

Originally Posted by Jim Carr

Assorted questions: Do you have a back-up head and/or cab for testing? Are you using an active bass? You said the effects/pedals are not involved. Care to elaborate how you know? Have you called Epifani?

The only other amps I have are combo amps but I just can't recreate the problem at home. Both of my basses are active and it's done it with both of those and also happened when a friend was sitting in with his bass. Haven't contacted Epifani yet since I haven't definitively determined that it is the cabinet.

[Largedon]

Originally Posted by dmusic148

+1 to Jim's post. Also, yes, it's possible that the crossover is the culprit, but very, very unlikely.
Years ago I had a pedal tuner that developed a problem and created exactly the problem you describe. I mean Exactly.

This is interesting, I just never thought a pedal would behave like this. Anytime I've had a pedal go out it's always been easy to diagnose. Maybe I'll spend some more time messing with the board and see if I can recreate it there.

So frustrating because if I could just get it to start doing it at home I could start removing things from the chain and go from there and narrow it down. I've got a couple of big gigs coming up next month and really would like to get this taken care of before then.

[Stumbo]

Originally Posted by Largedon

Rig worked fine for the next few gigs and then its done it again at the last two gigs I've played.

Seems to me that it may not be your rig. Maybe one of your pedals is overheating or has a minor bad connection/solder joint or maybe a cable is going bad?

If it happens at your next gig, as a test, I suggest you unplug all your pedals and go direct into your rig.

You can also try another rig at a gig with your pedal board and hear what happens.

[dmusic148]

Yes, intermittent problems are difficult to find. Do you use a Boss tuner pedal? Don't mean to throw Boss under the bus, but its the one I had, which caused the problem.