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Feedback problems with OP 40, and not OP30?

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omegaman
Posted 2003-12-31 1:42 AM (#198150)
Subject: Feedback problems with OP 40, and not OP30?


Joined:
December 2003
Posts: 28

Location: Chicagoland U.S.A.
I just upgraded from a Korean 2003 collectors ed. to a USA 2003 Collectors Ed. with OP 40. Plugged her into my Fender Acoustasonic and am getting feedback beyond the halfway mark on my preamp volume setting with the amp at levels that I was getting no feedback on the OP 30 with the Korean model. Cannot figure it really. I also plugged into my Mesa boogie F 50 and it is giving me the same reaction, there is no phase switch on the Mesa by the way. Thoughts? Is it the guitar or the electronics or what? The notch filter seems of no value, I find it confusing to use as the instructions are vague.

Thank you in advance...
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Paul Templeman
Posted 2003-12-31 5:39 AM (#198151 - in reply to #198150)
Subject: Re: Feedback problems with OP 40, and not OP30?


Joined:
February 2002
Posts: 5750

Location: Scotland
The major factor here is not the electronics but the fact that that you have gone from a plywood-topped guitar to a solid-topped, far superior guitar. The paradox here is that a cheaper less resonant guitar will usually be more feedback resistant. It's a general rule that the better a guitar is acoustically, the bigger a pain it becomes to amplify. Also remember that the pickups in each guitar are different & the original Ovation pickup in the USA guitar appears to have a slightly higher output than the Thinline in the Celeb, so you'll probably need less gain at the pre and the input stage.

As far as the preamps go, they are slightly different. According to the spec sheet the gain on both pre's is identical, but the EQ centres are not, so if you are using a "standard" or favourite EQ setting then the pre's will sound & behave differently. The Low eq on the Op30 is centred at 60Hz, but it's 84Hz on the Op40. 84Hz is closer to the guitars fundamental frequency than 60Hz, so a boost of more than a couple of Db is likely to encourage feedback. The mid & treble EQ centres are different also, but not to the extent that they should cause feedback problems. The other major difference is the overal frequency response of each preamp. The OP40 is 27Hz-90KHz while the 30 is 50Hz-100KHz and the Op50 is 40Hz-87Khz. God only knows why they want it that low but the fact that the Op40 goes down to 27Hz could also be a factor in encouraging low-end feedback. The preshape function includes a rumble filter, see if that helps, and experiment with the EQ. Always start with a flat setting and keep eq boosts to a couple of Db at the most, and don't expect the same settings you used on the Celeb Collectors to work for the USA Collectors

In my experience the notch filters work perfectly, are you sure you are using it correctly?
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omegaman
Posted 2003-12-31 8:19 AM (#198152 - in reply to #198150)
Subject: Re: Feedback problems with OP 40, and not OP30?


Joined:
December 2003
Posts: 28

Location: Chicagoland U.S.A.
Thanks for all of that Paul, you are making some sense to me although the meaning of the electronic nomenclature is tough for me to grasp. I am not sure just how to set the notch filter, can you offer some tips there? I will try your advice when I get home from work and see how it goes...thanks so much Paul...best regards
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Paul Templeman
Posted 2003-12-31 9:32 AM (#198153 - in reply to #198150)
Subject: Re: Feedback problems with OP 40, and not OP30?


Joined:
February 2002
Posts: 5750

Location: Scotland
Switch on the Notch filter on turn it all the way anti-clockwise. Make the guitar feedback (best to do this at a soundcheck or in a controlled environment, not during a gig!) You'll find it will want to feedback at two or more frequencies. Find the most prominent feedback frequency and try to get the feedback pretty constant. While it's feeding-back turn the notch control slowly through it's range. At some point in it's range the feedback will lessen or disapear completely. I know it sounds a little fiddly, but once you get the hang of it, it takes seconds. A set of Ovation "Airlocks" will help also. Al should be able to get a set for you.
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alpep
Posted 2003-12-31 9:42 AM (#198154 - in reply to #198150)
Subject: Re: Feedback problems with OP 40, and not OP30?


Joined:
December 2001
Posts: 10483

Location: NJ
Originally posted by Paul Templeman:
[QB]Switch on the Notch filter on turn it all the way anti-clockwise.

that would be counter clockwise to us "yanks"
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Paul Templeman
Posted 2003-12-31 9:47 AM (#198155 - in reply to #198150)
Subject: Re: Feedback problems with OP 40, and not OP30?


Joined:
February 2002
Posts: 5750

Location: Scotland
Sorry, I stand corrected. I do make an effort to screw up the English language so yous guys will get whatever the hell I'm rambling on about, but sometimes I don't quite make it.
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omegaman
Posted 2003-12-31 10:21 PM (#198156 - in reply to #198150)
Subject: Re: Feedback problems with OP 40, and not OP30?


Joined:
December 2003
Posts: 28

Location: Chicagoland U.S.A.
Your tips worked like a charm, feedback gone, even on the Mesa. I lowered the bass on the eq., kicked in the notch as you said, awesome!

And employed the shape thingamajig, as you said.

She cranks!

Best regards and Hapy New Year!
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TRboy
Posted 2003-12-31 11:52 PM (#198157 - in reply to #198150)
Subject: Re: Feedback problems with OP 40, and not OP30?



Joined:
February 2003
Posts: 2177

Location: the BIG Metropolis of TR
I LOVE IT WHEN A PLAN COMES TOGETHER!!!


****HAPPY NEW YEAR EVERYONE****


. . . . .
Mike :D
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peterbright
Posted 2004-01-01 12:09 PM (#198158 - in reply to #198150)
Subject: Re: Feedback problems with OP 40, and not OP30?


Joined:
December 2003
Posts: 420

Location: On the beach in Southwest Florida
Glad it worked out for you.
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