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Dirty-South Blues Harp forum: wail on! >
No feedback guitar amp
No feedback guitar amp
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eebadeeb
31 posts
Dec 03, 2011
6:55 PM
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I was just given a 10W eleca guitar practice amp. I tried it with harp using a standard sm58 and got plenty of volume and zero feedback even with all knobs full+ and mic touching amp. It would certainly be valuable info to me if someone could explain why this is so. My smokey, honeytone and Fender 35w guitar amp all feedback easily with this mic.
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5F6H
1009 posts
Dec 04, 2011
6:50 AM
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Does your SM58 have an in-line impedance transformer to convert from low impedance to high impedance?
You have gain, volume, treble & bass dimed & the overdrive button engaged?
My guess is that the amp & mic combination simply does not have enough gain to induce feedback. This makes life simpler in that you will find feedback easy to avoid, but it likely means that you are not exploiting the full potential volume that the amp can deliver (if you are just practising or recording then this might not hamper you).
For an amp to deliver full power it should really feedback before the volume pot is dimed, the trick is becoming familiar enough with the amp to determine where this happens, whether it be at "2" or at "8". In many amps being able to turn the volume pot fully up is not particularly helpful as some series resistance in the unused portion of the volume control helps reduce feedback & stop the tone from going too spanky.
Your Smokey amp has no attentuation of the signal (no "volume", "tone" or "treble/bass" controls) so has lots of gain & is always flat out, the simple tone control on the Honeytone may not be cutting as much signal as the tone stack on the Eleca. I would expect ANY 35W guitar amp to feedback. Some modern keyboard & old accordian amps feedback much later because they can be missing a preamp stage & have much less gain (keyboards have a preamp stage built in).
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www.myspace.com/markburness
Last Edited by on Dec 04, 2011 6:51 AM
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Greg Heumann
1364 posts
Dec 04, 2011
1:04 PM
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Mark, you beat me to it. I too would expect ANY amp, regardless of power to feedback with the mic held to the amp and volume knob at full unless the amp was specifically designed with exceptionally low gain - definitely NOT the case with the typical guitar amp. SO - either the amp is faulty (doesn't sound like it), the mic is faulty (might be) or you're using an XLR-to-1/4" cable which delivers something less than half of the mic's output to the amp (most likely.)
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/Greg
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