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Old 12-30-2004, 01:26 AM
jim_n_virginia jim_n_virginia is offline
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Default "A" string feedback

Just curious as to how many folks when they are plugged in to a PA suffer from the infamous "A string feedback syndrome"

I EQ the lows down. Make the sound kind of tinny.

What do you do for low noise feedback?

I plug straight into my PA, would it be easier if I got one of them Fishman Pro Platinum EQ boxes with the notch filter?

What about soundhole covers when playing plugged in, are they essential? I have one but have never used it.

As you can probably guess I know next to nothing about sound engineering.
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Old 12-30-2004, 01:27 AM
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That's when a notch filter comes in handy... it's a very limited cut and only cuts where you're getting the feedback. A soundhole cover can work, but I don't like them much...
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Old 12-30-2004, 01:34 AM
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It's funny, whenever I encounter a "wolf tone" (plugged or unplugged) it's usually the A string--either it resonates along with one or more of the braces or the open high E string causes the A to vibrate sympathetically (I'll pluck the open E, immediately damp it, and it'll still ring until I damp the A as well).
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Old 12-30-2004, 08:18 PM
4Gtrs 4Gtrs is offline
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There is something common about the resonant frequency of the A string. I first encountered it after we had finished our 'welcome & gathering' songs at church, with the guitar on the stand, me sitting with the congregation. It started as a low rumble, which grew in volume as folks looked around. The sound level grew and this possessed guitar was jumping on the stand! We now mute every open mic or instrument when it is not in use.
I also experience A string feedback with my acoustic bass. Our regular bassist, using a P-bass, also gets feedback through the PA. He no longer plugs into the PA. So, since it happened to three instruments, we surmised that it had nothing to do with the particular guitar(s) itself.
I understand that the 'correct' procedure is to use a 'pink' noise generator CD, then notch out the offending frequency (55, 110, 220 hz) on the PA equalizer. We haven't been able to do this because of some personal dynamics with the gent operating the PA (he packaged and installed the system). I'm almost certain notching the preamp would work, as it would decrease that particular frequency. I did attempt to attenuate the frequency using a Gigpro, however the cut isn't enough. The rubber plug 'feedback buster' helps immensely, but doesn't eliminate it completely for the higher volume songs.
Best wishes. The feedback really distracts my playing (I have enough trouble just keeping time) to the point that I am considering a thinline/semi-solid body acoustic.
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Old 12-30-2004, 11:46 PM
jim_n_virginia jim_n_virginia is offline
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THanks Wade I think I am going to start watching for the Fishman Pro Platinum EQ it has a notch filter on it plus I have been wanting volume control anyways.

Happy New Years all!
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Old 12-31-2004, 02:39 AM
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In our P&W Band, we've actually been blessed with few feedback problems, but we're also pretty anal about monitor and mike placement. The few times we've had feedback (from high-pitch earsplitting to the wolf howl), it was because a monitor was getting into a microphone.

For my guitars, I have Fishman USTs in both and have not had feedback problems at all. The Martin has the Prefix Pro preamp that includes EQ, Notch Fileter and Phase switch. The Taylor just has the Fishman UST and whatever inline preamp (there's no barn door) it came with. I do have a rubber sound hole cover, but I rarely use it. I do make sure my Martin's volume level is at zero when I'm not holding it. The Taylor has no volume control, but I connect it and my Martin to the PA through an A/B Box, so I make sure the Martin is selected and volume at zero when I'm not playing.

We've also found that if we take the bass through a DI Box (we use Beringher DI100s) first and then use the pass-through connection to go to the bass amp, that helps out a lot as well.

Of course, all of the above is based on my observations and experience being the lead "go-to" guy for sound problems, I have no training other than what I got from this forum (which has been a lot!) and the research I've done on the internet.

Good Luck!
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Old 12-31-2004, 07:10 AM
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Default Tons of options

Jim,

That soundhole muff will help a lot. On my HD28 it's the E. And dropped D is really lively!

If you're looking at preamps with notch filters take a look at the Baggs Para DI. It's has a Parametric EQ. Basically it allows you to pick the fequency (labeled as the actual note) and then contol how much cut you need. It's a bit more subtle than the pure notch filter. Some amps like the Rivera Sedona 55 also have this function.

You might also just start with playing with your monitor placement.

I've found using an amp and getting the sound behind me in as opposed to in front of me in the monitor facing the soundhole is helping.

And a 32 band EQ on the monitor feed along with one of those spectrum analyzers is a great way to find the exact frequency and eliminate it.

dbx also makes a unit called a Drive Rack PA. It is a processor you place between the poweramps and the speakers. It has a number of processors in a line including limiter, compressor, EQ, and auto feedback suppression. This unit is a great protection for expensive speakers, but what's really cool is it comes with an optional microphone that you hang in the space your going to play, set the speaker volumes to your desired level, and then use the pink noise generator to paint the room. The mic picks up the signals and automatically EQs the system to get rid of all those stray, bouncing, harsh frequencies. Now I'm sure a real sound guy will tell you he can set-up a room way better than this auto feature, and I'm sure he can, but not all of us can have a sound guy following us around. So using this system gets the EQ set-up right for the room, and it's amazing how much feedback one can eliminate when the baseline EQ is right for the room. The unit can then store those settings for multiple rooms.

I have one on our mains, and as soon as I can afford it, I putting one on the monitors.

Good luck.

max
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