What causes feedback in my PA system? - Audio Players & Recorders

sounds like an internal connection problem. open access panel and check the solder connection is not broken or loose. Be sure the metal mesh jacket is not touching the lead wire as that would cause a scratchy noise and feedback, or maybe near the internal cable causing feedback

The effects should be the same as the EPA900 unit. Get the brochure here and look for "Effects Table." Hope this helps! http://www.behringer.com/assets/EPA900_P0431_M_EN.pdf

You are proabably getting regeneration. This is nothing more than feedback as these acoustic guitars are good microphones. Make sure the guitar CANNOT "hear" the speakers of the PA system. Crank the high frequency EQ for that channel all the way down. This is common when soundment decide they ALSO need to boost the high frequencies of the PA up when they shouldn't. Regeneration is a feedback that is below that to fully sustain, but will cause a ringing "tail" on notes.

Proper level setting of the mixer is important. HOWEVER if the clipping is occuring at the speakers the only possible problem MIGHT be that you have a supersonic feedback that is saturating the speakers above your hearing range, Be sure you don't boost the highs too much with the EQ as this can cause the feedback that you can't hear. Also make sure that you power the speakers from the SAME receptacle as the mixer, even if it means running an extension cord to bring power to the mixer. This is to avoid a low frequency hum and common mode distortion/damage. A low frequency hum could cause the clipping.
It would be a good idea to get a sound meter to check the sound level. You should be able to reach 85 Db from this system without clipping. If you need more than that, you MAY need more speakers if the band instruments are too loud. Also if the band has amps that get into the vocal microphones that adds to the clipping level... make sure the mics don't "hear" the band instruments. Make sure your speakers are toward the audience from the mics to avoid the supersonic feedback problem. If the vocalists can't hear themselves with that configuration you need to set up seperate stage monitors.

There are some pretty good videos on YouTube about proper mixer level setup.

The correct distance is when the feedback goes away - avoid placing the microphone directly in front of the speakers.

The main mix controls ALL outputs simultaneously.

The mic channels are controlled individually by the sliders.

It sounds like you are on the verge of feedback where the mics are picking up the PA speakers.

Make sure you have loaded the support SW and make sure you have disabled ECHO as the mics may be looping back through the computer causing the rattle.

are they still under warranty?
Worth checking into ... JBL has a good warranty program for this series and local authorized repair centers ... if you are under warranty you could have a fix for free in about a week ...

For audio expertise and PA system help with feedback and noise, try our new DVD "PA Systems for Small Groups" at www.rexark.com

We have the same phones in our office. The feedback happens with our phones if the handset is left on the base. Picking up the handset and speaking through it as if your are on a phone call during the page should solve the problem of the feedback. If not, you may want to look at your P.A. system settings.

The feedback unit should be connected between the pre-amp section and the power amp section. As you descrubed the ST-out and P.Amp IN are the ones to use.

Dan

WRONG INPUT?