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Dirty-South Blues Harp forum: wail on! > Anti feedback...easy way
Anti feedback...easy way
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Jehosaphat
365 posts
Dec 05, 2012
8:07 PM
Feedback and how to control it always generates discussion on any Harp forum..I for one have always had problems with it caused by any number of things...too loud bands,trying too hard to get some overdrive on amps etc etc.
Anyways a while back i scored a reasonable deal on a Blues Deville..great amp in its own way but without some fairly serious modifying it can be a Feedback monster.
Thing was when i went to pick up the Amp the guy said he had a Boss GE 7 equaliser sitting around and would i be interested in it for 50$.Well any pedal for 50 bucks seemed a good deal so i bought it thinking that i could resell it for a 100 or so and (for a change)actuallly make some money on a deal.
Thing is i now wouldn't part with it for less than a grand..This thing is brilliant.
Ok i switch the amp on and dial it and my mike to the edge of feedback then i start notching some of the frequencies down bit by bit or in the case of anything above 1.6k hz or below 200Hz cut them completely.
Then by very gradual edging up of the'fat' frequencies i have effectively allowed myself another few DB of volume with the added bonus that the sound is definately fatter.
But another great thing is that i use a Bb harp to set my gear up ,the reasoning being that it is in the middle range but even then sometimes a D harp (or F) still has a bit of shrillness about it.
Problem solved: lean over and drop the 1.6K slider down a tad and suddenly the D or F have a more solid less shrill sound.
This Pedal is magic...anyone else using one in their rig?
Rick Davis
976 posts
Dec 05, 2012
9:19 PM
Yes, I have it on my pedal board but I seldom use it. It does work very well for what you describe: Taming a feedback-prone amp like a Blues Deville. Very good pedal.

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-Rick Davis
The Blues Harp Amps Blog
rogonzab
177 posts
Dec 06, 2012
2:52 AM
"the'fat' frequencies" are....?

I was thinking to buy an EQ for my self, and try to make my 8" amp more "bassier" (That is the word?)
It is possible?
rainman
39 posts
Dec 06, 2012
3:21 AM
Rogonzab, The Lone Wolf Harp Tone+ is a great pedal for doing just that. The pedal is really a 2 band equalizer with a range of 20db +/- for bass and treble frequencies. It helps reduce feedback as well.
rogonzab
178 posts
Dec 06, 2012
4:13 AM
The Tone+ is (I think) the perfect pedal for me. But right now is way to expensive for me. Betwen taxes and shipping the cost of the pedal is close to the 80% of my salary.

I am looking one of those Joyo pedals. They are $40 each, and true bypass. I guess that will help while I save for the real one.
htownfess
271 posts
Dec 06, 2012
4:20 AM
rogonzab, what people call "fat" for harmonica is technically located @ 240 Hz, but an EQ device will usually have a 200 Hz slider, which is more than close enough. However, it will not necessarily make an enormous difference; beyond a couple of dB increase, you may notice no improvement from the pedal alone. You may also be able to milk a little more beef out of the 125 Hz band commonly found on EQ pedals. The Lone Wolf Tone+ pedal is more specifically tailored to harp freqs, as rainman notes, and pushes the "fat" range somewhat harder IMO (I've had a 16-band mono EQ for a couple decades), but the results are still going to be constrained by the nature of your unnamed 8" amp.

Edit: Meant to say 200 Hz slider, not 250

Last Edited by on Dec 06, 2012 5:43 AM
rogonzab
179 posts
Dec 06, 2012
4:34 AM
htownfess,

I am aware of that. I just want to make my amp a litle better (I guess we all do that when we are searching for the best tubes, or speaker or settings)
htownfess
272 posts
Dec 06, 2012
5:42 AM
+1 on that, it's worth doing what we can when we can.

If you can get a $40 pedal with a 250 Hz or 200 Hz band control, that will directly affect what you're after, and is a good tool to have around.

The thing with turning up the "fat" 200-250 Hz bands is that it's like turning up the bass knob on a big Fender amp like a 59 Bassman reissue: there's a point at which you get the maximum clearly projected bass, and past that, the sound "muddies up." Sometimes the latter sounds good for softening or rounding off the overall tone, so long as it doesn't bring on bass feedback.
Rick Davis
977 posts
Dec 06, 2012
7:24 AM
Why is 240 Hz the "fat frequency?" That is a note between A and B below middle C. Wouldn't the fat frequency depend on the harp, amp, and room? Isn't that the point of having a graphic EQ in the first place?

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-Rick Davis
The Blues Harp Amps Blog
5F6H
1446 posts
Dec 06, 2012
7:41 AM
Hi Rick,

It's not necessarily just the fundamental frequency of the played note that dictates percieved "fatness", it's as much where the harmonics (perhaps an octave below the fundamental) that provide that fatness live. If you heavily scooped the frequencies between 200Hz & 400-500Hz it doesn't matter what key harp, or note you played, the sound wouldn't have the same "body" to it.
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Rick Davis
978 posts
Dec 06, 2012
8:21 AM
Mark, yes, I know that. No doubt, if you pulled down all the low mids the sound would suffer. That is why I asked why htownfess said the fat tones for harmonica are "technically located @ 240 Hz." That is pretty specific.

Mark, how are subhamonics created in the harp amp signal chain? Is it a function of the speaker deforming?


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-Rick Davis
The Blues Harp Amps Blog

Last Edited by on Dec 06, 2012 8:29 AM
Rick Davis
980 posts
Dec 06, 2012
10:22 AM
If you are playing in the key of A, for example, your tonic note is 440 Hz. That's gotta be your fat zone, right? And I'm not sure harp amps create sub-harmonics below the fundamental.

I'm trying hard to understand why 240 Hz is so important. What am I missing?

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-Rick Davis
The Blues Harp Amps Blog
5F6H
1447 posts
Dec 06, 2012
3:07 PM
That 440Hz might simply be 440Hz, and sound thin & cold (run a 440Hz clean sine-wave into your amp), it's what's around it that makes it fat. We generate harmonics even when we play acoustically (ideally). The amp should put out at least what we put in, within reason, when relatively clean. As you push an amp into distortion it tends to shift the focus upwards frequency wise.

Get an A harp, play some 1st position in the low end, then use your EQ to shelve everything below your 1blow (220Hz or as near as you can get) what happens?

On a diatonic the lowest note a lot of folk will play will be G 196Hz, but in practice you need to reproduce way lower than that for a full sound.

The human ear typically gets into it's stride & is most attuned to sounds from around 200-250Hz (though you can usually hear from under 50Hz) up to the 8kHz range, ~2kHz to 5kHz being the most sensitive portion.

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bonedog569
735 posts
Dec 06, 2012
3:57 PM
I've been messing a bit with eq pedals recently - for use with my blackface deluxe reverb. Pushing the 200 hz slider up can generate low end rumble feedback pretty quickly. No free lunch.
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Rick Davis
983 posts
Dec 06, 2012
4:35 PM
My understanding is that harmonics are divisions of the fundamental tone, so they are always higher and never lower (unless you have a sub-harmonic synth).

The little Boss EQ7 pedal is pretty cool. It can adjust + or - 15dB on seven bands, and + or - 15dB overall. The Lone Wolf Harp Tone+ pedal is an active EQ too, but with fewer bands.

When I use the EQ7 pedal I have the sliders in a frown pattern, the opposite of the smile you see on the EQ on many PA boards. I roll off the highest and lowest frequencies a bit to get rid of that low rumble feedback and the high squeal feedback. The 200 Hz band gets diminished a bit. That is why I was curious about all this. In the video I made about the EH 44 Magnum amp pedal you can hear the effect of this: it is the last pedal I click in the middle of the video. Advance the vid to about 1:20.



Jehosaphat's original topic was about using this pedal for feedback control. I think it does a pretty good job of that, too.

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-Rick Davis
The Blues Harp Amps Blog

Last Edited by on Dec 06, 2012 4:37 PM
dougharps
300 posts
Dec 06, 2012
10:22 PM
It isn't necessarily harmonics alone that can give fat tone. If you play more than one note (chords), especially with a just intonation or compromise intonation harp, you can get difference tones that will be lower in frequency than any of the fundamental tones, and really fatten up the sound.

Edit to add: Because each amp/mic combo is different, I suggest when using an EQ, start with a flat EQ, use your ears, experiment, and see what settings work best for you with that combination.
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Doug S.

Last Edited by on Dec 06, 2012 11:07 PM
5F6H
1448 posts
Dec 07, 2012
2:58 AM
@ Rick "My understanding is that harmonics are divisions of the fundamental tone, so they are always higher and never lower (unless you have a sub-harmonic synth)."

Interesting discussion Rick - Yeah, but the harmonics of what? If you the player & the peculiarities of the instrument give rise to apparent subharmonics at source, the amp will reproduce these until pushed to the point where it primarily accentuates higher harmonics...I guess when things go really non-linear that all bets are off when components are failing to produce clean tone and what happens "happens"?

If the harmonica can only produce the fundamental tone and harmonics above it, how do folk achieve "fat/deep" tone whilst keeping correct pitch and playing a single note? (A genuine question, I'm no expert in acoustic physics and am just as keen to have this explained to me).

"On the other hand, if a reed is set too low, the suction flow will not generate enough tension energy for the reed to come to full amplitude right from the start. Reeds that are set too low will speak right away with low or moderate air pressure, but will produce a ‘thin’ sound, which misses some of the lower harmonics due to insufficient reed swing. If the air pressure is high at the moment the key is
pressed, the reed won’t speak at all."

...taken from www.concertinaconnection.com


In "Reed vibration in lingual organ pipes without the resonators." Miklós A, Angster J, Pitsch S, Rossing TD...

"The appearance of subharmonics is explained by taking into account the periodic modulation of the stress in the reed material by the sound field. Therefore, a parametric instability appears in the differential equation of vibration, leading to the appearance of subharmonics."

If there is nothing happening at 200Hz with a diatonic higher than G, what is there to boost, or cut, with an EQ?

Perhaps David Payne might be able to shed some light on the subject?


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Last Edited by on Dec 07, 2012 3:29 AM
colman
213 posts
Dec 07, 2012
3:32 AM
all this discussion is about fat tone and feed back and it`s important to study all aspects.,but if you have a thin non resonating tone comming out of your mouth, all the hot amp in the house is going to help you.there`s a woodshead job for a harper ,to develop
a tone that rings with overtones and can cut it thin like a razor on a note then back to the fat sound...
the amp is icing but real control of a harp in your mouth is the cake.......also:i just cut the highs 2,
and around 7 on mid&low`s and i can usualy turn up to 7 or 8 on volume on a champ,30/65 musicman,silvertone twelve,or a fender twin.works for me for 42 yrs.
Rick Davis
985 posts
Dec 07, 2012
7:31 AM
Mark, yes, very interesting. Your quote about sub-harmonics in organ pipes seems to plausibly explain what happens with blues harp. I mean, our ears tell us the best players get sub-harmonics -- or they certainly seem to.

I need a spectrum analyzer...

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-Rick Davis
The Blues Harp Amps Blog
willymmx
1 post
Jan 10, 2022
7:13 PM
I just wanna say thanks to Jehosaphat. Just cutting that 1.6k freq was the solution to fight against the feedback. Problem solved with just a cheep Joyo EQ. Thanks again from Argentina. All the Best!
garry
798 posts
Jan 13, 2022
6:51 PM
For those playing through a wireless rig, I've found that it helps a lot to just not be standing in front of your amp. At the jam I attend, the only place I can plug in is on the opposite side of the stage from where I stand. And I can turn my amp up past the feedback point without t being a problem. It's a little weird, because I can't really hear it as well, or tell how loud it is in the room. But in loud situations I generally can't hear myself anyway, and this at least ensures that the audience can.

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SuperBee
7033 posts
Jan 13, 2022
10:18 PM
lol, the member formerly known as Jehoshaphat.
I used to read these feedback related posts with great interest. They’re good. I learned lots of things to try and eventually I worked out some stuff.
Number one best fix was to get a band which could turn down.
Frequency cuts helped too, before I sorted out fix number one.
There’s another thing I just worked out more recently which works where you can mic or line out the amp, which is to set it in front of you and facing you, much like a vocal monitor wedge.
But the boss ge-7 pedal which indigo, I mean Jehoshaphat, mentioned in op is interesting and I still should get one to go with my sonny jr. Gary O wrote a addendum to his SJ2 owners manual which advocated for the use of this pedal with the amp not so much as a feed back solution but just to get a great sound. I still haven’t tried it because frankly the amp sounds pretty great by itself and I’ve given up using any pedals with it but this is something which should be explored
2plankr
98 posts
Jan 17, 2022
5:11 PM
Couldn't you just use a "Little Fatty" pedal from Memphis Blues Amps?


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