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Dirty-South Blues Harp forum: wail on! >
Taming Feedback
Taming Feedback
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HarpNinja
2335 posts
Apr 16, 2012
8:30 AM
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Has anyone experimented with EQ's, noise gates, or high/low pass filters? These seem to, in theory, be good tools.
I've heard around 8,000Hz is going to be shrill and feedback often happens in the 800Hz, 1,000Hz, or 3,000Hz range. Honestly, I am not sure the frequency range of amped harp.
I think the Kinder uses a noise gate combined with some sort of filtering - maybe not notch filtering - but other devices tend to boost/cut frequencies for feedback.
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Mike
VHT Special 6 Mods
Quicksilver Custom Harmonicas - When it needs to come from the soul...
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7LimitJI
651 posts
Apr 16, 2012
8:41 AM
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Randy at Lone Wolf is working on a new pedal.
He posted this on the LW forum:-
Just wanted to give a shout out and let everyone know that I am working on an anti-feedback pedal. It should be ready early next year, it may seem like a long way off but it takes time to do things right. :D
Features to include:
1. Noise gate control
2. A mid frequency notch filter control
3. A high frequency notch filter control
4. Pedal will run on a 9v power adapter
5. Buffered high Z input and output
6. No solid state distortion
The noise gate itself will do a lot in reducing feedback by reducing the coupling between the speaker and the microphone and when the player begins to play the level of the harp will be above the noise gate level and allowed to pass to the amp. If the noise gate level is set from low to medium it will not be noticed but if it is set too high it can effect soft playing. I may not be explaining this well enough and will be working on an better explaination.
The notch filters are tunable to notch out the offending feedback frequencies. They are very narrow filters and will not negatively effect tone.
Set up will be:
1. Position yourself and your amp to where you expect to be playing
2. turn up amp to desired volume, if feedback occurs before you get to the desired level increase the noise gate to the point where soft playing can still pass to the amp.
3. Continue to increase volume. In the event feedback occurs again tune the high frequency notch filter until it is eliminated.
4. Continue to increase volume slightly above the desired level and if feedback returns use the mid frequency notch filter to eliminate it.
5. Turn the volume back down to the desired level.
It should only take a few tries to get the hang of it, just set the noise gate and notch out the feedback frequencies.
The expected price is to be $190.00
Thanks,
Randy Landry
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The Pentatonics Reverbnation
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"Why don't you leave some holes when you play, and maybe some music will fall out".
"It's music,not just complicated noise".
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HarpNinja
2336 posts
Apr 16, 2012
9:01 AM
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I'd buy one, lol! What I don't get, out of ignorance, is how limited notch filtering like that works.
Like what frequencies are we talking? I get that you can either notch a frequency, or have it notch out the frequency with a slope into others, etc.
I think the noise gate idea makes total sense. I also believe there are two types - a normal one and a hard gate. The hard gate is probably "better" and more transparent, but Randy's must be a regular noise gate as there aren't controls for opening and closing.
I have not clue how the Kinder works, but it is unusable with my current rig as it doesn't let you use a totally clean signal. It is fine for amped harp, but wouldn't work for beatboxing.
My solo rig doesn't really feedback, but access to gates and eq's on the POD make me wonder about trying to set up a way loud patch in hopes of learning how to help others control feedback.
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Mike
VHT Special 6 Mods
Quicksilver Custom Harmonicas - When it needs to come from the soul...
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5F6H
1145 posts
Apr 16, 2012
10:36 AM
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@ Harpninja "I've heard around 8,000Hz is going to be shrill and feedback often happens in the 800Hz, 1,000Hz, or 3,000Hz range. Honestly, I am not sure the frequency range of amped harp."
I don't think it is helpful to think of feedback purely as frequency related. Up to a point the more highs in the mix then the more likely feedback is to occur, but there comes a tipping point where cutting back highs adversely affects tone & fidelity...your ear will tell you when you have passed it.
8000Hz is typically beyond the range of a typical guitar speaker's high frequency (for one speaker, as you add more of the same speakers to an array the response range widens). However, you can still hear the effects of putting higher frequencies than this through the amp - e.g. when using a mic with a higher frequency response & noticing improved "edge/clarity/detail", or using the Presence control on a Tweed/Brown Fender (works around the 12KHz range).
The lowest commonly played note is 1 blow on a 365 or 64 Chrom (~130Hz). The highest note is 10 blow on a F harp (~2794Hz). Ideally you want an octave's leeway at either end to capture full harmonic range, so 65HZ to 5.6KHz...though more realistically resonant frequency of many guitar/harp speakers might be more like 80-95Hz.
But here's the thing, any device with a lot of gain will still feedback at frequencies that you need to use. Many factors affecting this gain & feedback can't simply be altered by turning your EQ controls. However, add-on devices like Randy's proposed pedal and Kinder's AFB+ will always have a market for making "so so" amps more useable & easier to get along with.
Also consider realistic expectation - if you are getting 5 or so Watts out of your single 6V6 amp, then it's doing the job. On the other hand if you are only really getting 20W out of a 100W rated amp, then you need "help".
For vocals, & I guess vocal effects, you do need better clarity than for harp alone, which may be why the Kinder isn't so good for you when beatboxing...but then I guess any device aimed at reducing "harp feedback" may have the same issue regarding vocals and a compromise might be needed unless you can rig up dedicated channels for each?
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www.myspace.com/markburness
Last Edited by on Apr 16, 2012 12:41 PM
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hvyj
2335 posts
Apr 16, 2012
10:48 AM
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I've fooled around with gates quite a bit. In theory, they work fine. In practice, if you use delay or reverb you lose the "fade" on the delay or reverb since the gate cuts it off. Then, if you set the threshold of the gate low enough to accommodate the "fade" or to accommodate soft playing, it isn't set high enough to prevent feedback. I used to use a gate, but don't these days.
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lumpy wafflesquirt
560 posts
Apr 16, 2012
1:01 PM
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Feedback can occur at different frequencies in different venues with the same rig. I can't remember the details, but it is to do with the distance the sound has to travel to get from speaker to mic relative to the wave length of the sound.
If you have a graphic equaliser on the amp you can do similar to the above, turn up the volume until it feeds back and them fade out the band on the graphic equaliser that is feeding back [it doesn't take many goes to work out which one you need first but it won't always be trhe same one]. Then turn the volume up further till it feeds back again and take down that band on the graphic equaliser. Then turn the amp down to the proper level for the gig and what ever you do [short of standing right in front of the speaker you shouldn't get feedback. It always worked for me in a big band situation with 6 mics in a peavey mixer amp.
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"Come on Brackett let's get changed"
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HarpNinja
2338 posts
Apr 16, 2012
1:02 PM
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Went home for lunch...stupidly erased a FANTASTIC patch, but managed to get most of it back. The POD computer interface needs an undo!
I took a totally clean patch and a Bassman patch. I added a noise gate, high pass filter at 80hz, and a high pass at 8000hz. This netted only positive effects in tone and feedback resistance. Remember, I am using a monitor which has a wider spectrum than a guitar speaker, so there needs to be some dialing out of things.
I then took a studio eq and adjusted 1000hz, 2000hz, and 3000hz to taste. This made a huge difference in tone (for the positive) and feedback. I think the most I subtracted was 3db or so.
With the Bassman patch, I then went after tweaking the final tone by using the amp controls. This let me dial in the fight kind of treble and presence.
This made a HUGE difference in volume. I already could get to too loud for solo sets volume, but this was more large amp volume.
The only issues at that stage were some boomy feedback that I dialed out via the cab parameters.
I then turned the patch down to where my other patches are and listened for a huge difference in tone, which there wasn't.
This was in about 15min of work. I am sure I can do a better job with another few minutes. I am mad as I had found THE sound and then accidently changed amp sims erasing all my Bassman settings. I got is mostly dialed back.
Conclusion: It is worth the effort do eq patches to keep nasty sounds for harp from being recreated in a PA speaker. I thought the cab sims would do this, but it is too touch compared to a simple studio eq in the chain.
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Mike
VHT Special 6 Mods
Quicksilver Custom Harmonicas - When it needs to come from the soul...
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