Distorting Amp

If the sound starts to distort after about 30 minutes, then that sounds to me like some of the circuit components are going bad. Capacitors in particular can go bad after some years of use, and other components may as well. You could have a skilled amp tech re-cap and calibrate it, or you could sell it off to somebody who wants a repair project.

 

Definitely the amp. If the speaker isn't distorting when the amp isn't, then the speaker is fine. Either way, don't sweat it. Sometimes you have to put money into your gear if you want to keep it working. You forget about the money eventually.

 

Hey, since you two guys are here (bongomania & JimmyM) - I got a new MoMark 500W yesterday - oddest thing (to me) happens ..
I inadvertently cranked the high (treble) knob on the EBMM Bongo all the way up, and stepped over to the amp - and got the most ungodly high pictched squeal. The amp was a 1/4 power through a single Avatar 2x12 (which is a good speaker, no issues with other amps). The feedback squeal is sensitive to (a) proximity of the bass to the amp and (b) amp volume. Turning the volume or the treble back down, or backing away from the amp solves the problem...and I'd probably never do that (dime the treble on an active bass and stand within 6" of the amp) but have never ever had that happen with any combination of gear I've had before.
What's up with that? The Bongo has a single coil + HB configutation. Hot coil + hot amp?

 

Hot coil, and more particularly a resonant peak in the circuit at a frequency that the treble knob boosted. By "circuit" in this case I actually mean the entire feedback loop from the bass to the amp out the speaker through the air and back into the bass. You never know when you'll hit a "perfect storm" where all of the parts are boosted, sensitive, or resonant at the same frequency.

 

Thanks B-mania; haven't had that issue since, but of course haven't tried to duplicate it either. Interesting but hard to characterize differences between the MoMark and LMII.

 

Hahaha....so true.

 

How to deflect a thread completely away from the question the OP asked!

Paul

 

What speakers are you using with the amp?

Paul