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IggyT · June 26th, 2009, 02:27 PM

Twice last night during rehearsal we had episodes of uncontrolled harmonic or symapathetic feedback with my Blues Jr first and then my friend's hot rod deluxe. In both cases we had to turn the amp off to shut this down.. the two amps were facing each other in the room with two vocal mics running into a separate PA.
anyone ever experience this?? I thought my amp was about to explode!
iggy

Wally · June 26th, 2009, 03:05 PM

Iggy, if this problem has never evidenced itself before, then I am going to think that it is sort of like telling a doctor that it hurts when I do this and the doctor says..."Don't do that anymore." lol
Don't fave the amps toward each other. Don't face the amps toward the mics in close proximity.
IF the problem comes up with more 'normal' arrangement of amps/mics, then you have a problem. I am going to think that the problem won't bother you again...unless you repeat that set-up.

IggyT · June 26th, 2009, 05:26 PM

so far a one shot deal; when his amp went into self oscillation mode like an air raid siren I suspected it was something to do with orientation....
iggy

Wally · June 26th, 2009, 05:38 PM

AS always...it isn't a problem until it reoccurs.

IggyT · June 26th, 2009, 08:16 PM

thanks wally...I will followup if it continues
iggy

e-merlin · June 26th, 2009, 11:05 PM

Sounds like new tube time for both of you. Microphonic tubes, more than likely.

Cleeve · June 26th, 2009, 11:28 PM

Were the reverbs on? Wooden floor? Floor monitors? Everything could have coupled just right to shake the reverbs pans..

IggyT · June 26th, 2009, 11:52 PM

yes...reverb on about 3 or 4..concrete floor..
iggy

Cleeve · June 27th, 2009, 12:06 AM

Hmm still mighta been the reverbs acting like microphones, if a standing wave were set up. My vibrato pedal of all things is microphonic, sorta freaky- modulated washing machine howling action with the guitar all the way down if it's too close to the amp.

IggyT · July 2nd, 2009, 09:40 AM

Quote:

Originally Posted by Cleeve

Hmm still mighta been the reverbs acting like microphones, if a standing wave were set up. My vibrato pedal of all things is microphonic, sorta freaky- modulated washing machine howling action with the guitar all the way down if it's too close to the amp.

I had the experience again last night..howling air raid siren noise...turning guitar volume down did nothing....I stomped the delay off..and SILENCE..other than good guitar sounds...this pedal was about 2 to 3 feet from the amp... so maybe that is the problem...really freaky !

Wally · July 2nd, 2009, 12:46 PM

YEp, eliminating variables is the best way to find out where the problem lies.

June 26th, 2009, 02:27 PM	#1 (permalink)
IggyT Tele-Holic Join Date: Apr 2008 Location: toronto Age: 50 Posts: 593 12 Photos	runaway harmonic feedback ??!!! Twice last night during rehearsal we had episodes of uncontrolled harmonic or symapathetic feedback with my Blues Jr first and then my friend's hot rod deluxe. In both cases we had to turn the amp off to shut this down.. the two amps were facing each other in the room with two vocal mics running into a separate PA. anyone ever experience this?? I thought my amp was about to explode! iggy __________________ I must have had music lessons...." Reverend Jim from Taxi

June 26th, 2009, 05:26 PM	#3 (permalink)
IggyT Tele-Holic Join Date: Apr 2008 Location: toronto Age: 50 Posts: 593 12 Photos	so far a one shot deal; when his amp went into self oscillation mode like an air raid siren I suspected it was something to do with orientation.... iggy __________________ I must have had music lessons...." Reverend Jim from Taxi

June 26th, 2009, 08:16 PM	#5 (permalink)
IggyT Tele-Holic Join Date: Apr 2008 Location: toronto Age: 50 Posts: 593 12 Photos	thanks wally...I will followup if it continues iggy __________________ I must have had music lessons...." Reverend Jim from Taxi

June 26th, 2009, 11:28 PM	#7 (permalink)
Cleeve Tele-Meister Join Date: Feb 2009 Location: Fayetteville, AR Age: 44 Posts: 499	Were the reverbs on? Wooden floor? Floor monitors? Everything could have coupled just right to shake the reverbs pans.. __________________ -Clint

June 26th, 2009, 11:52 PM	#8 (permalink)
IggyT Tele-Holic Join Date: Apr 2008 Location: toronto Age: 50 Posts: 593 12 Photos	yes...reverb on about 3 or 4..concrete floor.. iggy __________________ I must have had music lessons...." Reverend Jim from Taxi

June 26th, 2009, 03:05 PM	#2 (permalink)
Wally Poster Extraordinaire Join Date: Mar 2003 Location: Lubbock, TX Posts: 6,009	Iggy, if this problem has never evidenced itself before, then I am going to think that it is sort of like telling a doctor that it hurts when I do this and the doctor says..."Don't do that anymore." lol Don't fave the amps toward each other. Don't face the amps toward the mics in close proximity. IF the problem comes up with more 'normal' arrangement of amps/mics, then you have a problem. I am going to think that the problem won't bother you again...unless you repeat that set-up.

June 26th, 2009, 05:38 PM	#4 (permalink)
Wally Poster Extraordinaire Join Date: Mar 2003 Location: Lubbock, TX Posts: 6,009	AS always...it isn't a problem until it reoccurs.

June 27th, 2009, 12:06 AM	#9 (permalink)
Cleeve Tele-Meister Join Date: Feb 2009 Location: Fayetteville, AR Age: 44 Posts: 499	Hmm still mighta been the reverbs acting like microphones, if a standing wave were set up. My vibrato pedal of all things is microphonic, sorta freaky- modulated washing machine howling action with the guitar all the way down if it's too close to the amp. __________________ -Clint

July 2nd, 2009, 12:46 PM	#11 (permalink)
Wally Poster Extraordinaire Join Date: Mar 2003 Location: Lubbock, TX Posts: 6,009	YEp, eliminating variables is the best way to find out where the problem lies.

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