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Topic: Where is the distortion coming from? |
Michael Hummel
From:
Ottawa, Ontario, Canada
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Posted 27 Sep 2012 9:11 am |
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New to pedal steel, but 50 years playing 6-string electric. I also happen to be an electronic engineer so I know my way around circuits and signals.
My Sho-Bud Pro III has a humbucking pickup on the E9 neck (a knowledgeable forum member thinks it is a Bill Lawrence 710).
It's pretty obvious that the signal from a pedal steel pickup is an intimidating one for any amplifier circuit. I am finding that all of the amplifiers or modelling pedals I have tried have a faint trace of distortion when I play several notes simultaneously. It's not the usual intermodulation distortion you hear when playing two or three notes through an overdrive pedal, but rather a crackly sound.
Turning the input gain way down on amplifiers/pedals doesn't seem to make much difference. Backing off on the volume pedal doesn't seem to make much difference.
This is a fairly subtle thing and I think most people wouldn't notice (except fellow steelers, of course!) but it is bothering me. Is this a common occurrence just because of the complexity of a psg signal, or has anyone experienced a problem like this with a pickup, or some other wiring in the guitar?
(Sorry if this belongs in the Electronics section, but to my way of thinking it is an issue with the overall guitar).
Would appreciate anyone's thoughts on the matter.
Mike
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MSA Classic 5+4
Too many 6-strings and amps to list |
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Bud Angelotti
From:
Larryville, NJ, USA
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Posted 27 Sep 2012 10:13 am
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Plug the steel straight into your amp, clean channel, no reverb or effects. No volume pedal, extra cables or gadgets. Does it still distort? Try another amp. Does it distort? If it does you either have 2 amp problems or 1 pickup or contact problem. And make sure the one cable you use is a good one. it should not distort. Mean & clean.
_________________
Just 'cause I look stupid, don't mean I'm not. |
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Hook Moore
From:
South Charleston,West Virginia
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Jack Stoner
From:
Kansas City, MO
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Posted 28 Sep 2012 3:58 am
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If it's a Lawrence 710 pickup, it needs to be 3/8" below the strings (I have 710's on my Franklin and they are set a "loose" 3/8"). Too close and as Hook notes it can distort. The Lawrence is a great pickup but it is also a high output pickup.
I use a POD XT and do not have any distortion problems running directly from the guitar to the POD.
Here is a picture of a Franklin (for sale) that has Lawrence 710 pickups on it, for reference to what you think is a 710 pickup.
http://bb.steelguitarforum.com/viewtopic.php?t=233895&highlight= |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 28 Sep 2012 6:51 am
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| Quote: |
| Is this a common occurrence just because of the complexity of a psg signal... |
Speaking from an engineering standpoint, what would make you think of a psg signal as "complex"? Compare it to a reproduction of another instrument, such as piano or organ, where notes played simultaneously are often several octaves apart, and you'd have to admit that the psg normally emits a reletively simple frequency structure.
As to what you are hearing, that is difficult to ascertain. To be sure, there is some intermodulation distortion going on, and it increases when you ask a single speaker to reproduce a more and more complex waveform. To simplify your investigation, I would suggest that you try different amps and speakers, and see if you still hear the artifacts that are troubling you. Do you notice these artifacts on the recordings of other players? If not, it's likely that there may be a problem somewhere in your own sound chain. |
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Jim Bates
From:
Alvin, Texas, USA
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Posted 28 Sep 2012 11:11 am
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Other things to check: Check the solder connections on the speaker jacks on the amp; all jacks on the amp chassis; the neck selector switch on your guitar, and the wire solder joints; the volume pedal pot also can have 'dirty spots'; make sure all pots on amp are clean; and do not forget to check the cords for noisy spots (twist and wiggle the cord while playing the chords). All of these things have happened to me through the years. All the above suggestions before mine, I also agree with.
Thanx,
Jim |
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Johan Jansen
From:
Europe
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Posted 29 Sep 2012 1:13 am
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Combination of wider space to the strings and taming the output, with a pre-amp that can be squeesed. Works great for me!
JJ |
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Georg SΓΈrtun
From:
Mandal, Agder, Norway
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Posted 29 Sep 2012 3:50 am
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That you hear a "crackly" sound when playing chords, sounds familiar. I may or may not be right in what goes on in your case, but the following is a description of how sound-chains handle PSG.
Hot PU on a PSG, into a relative high-ohm input, means subharmonics get through - producing strong beating between notes. As these subharmonics go all the way down in frequency to where they affect the DC levels through the first stages of the sound-chain, with all audible sound overlayed on the varying DC levels, VP pots, capacitors and active stages get pushed out of DC-balance into saturation in sync with the subharmonic beating, resulting in what can best be described as "a crackly sound". Later stages in the sound-chain will then amplify this minute "crackling", and not the subharmonics and swinging DC-levels themselves as there are plenty of high-pass filtering and decoupling in and between these later amp-stages to reduce the DC-swing to nothing.
More on the issue...
In set-ups with passive VPs first, the DC-swing tends to result in rapid wear and scratchy pots since pots are not handling DC variations well - pots in sound-chains are for handling AC (sound waves above a certain frequency) only.
Input capacitors in amps and effect units get charged out of zero balance, feeding DC back towards previous stage - the VP if that comes before them. This "DC feedback" disturbs and amplify imbalance in previous stages that do not load it hard enough to zero it out continuously, which is why passive VP pots are so vulnerable and won't last long in certain set-ups.
Solution...
Dampen DC swing caused by subharmonics from the PU as much as possible, before it enters passive VP pots and the amplifier's input. Easier said than done in some set-ups, but various match-boxes and active VPs made for PSG usually do just that.
I used trial and error to find the right match-box combo for controlling subharmonics without "killing" them, and keep the DC levels stable. Means I can hear the beating and balance the bar to reduce/eliminate them, and still have the solid bottom (low frequency) sound I want.
Advice: Try out various match-boxes as first stage, and see if that won't reduce the irritating "crackly" sound you're hearing now. |
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Bob Hoffnar
From:
Austin, Tx
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Posted 29 Sep 2012 7:39 am
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I had that same problem with the 710. I'll join in with the back the pickup off the strings solution. Or you can put a buffer of some sort between the steel and volume pedal. If you are using an old Fender amp try plugging into the 2nd (attenuated) input.
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Bob |
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Jim Bates
From:
Alvin, Texas, USA
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Posted 29 Sep 2012 8:05 am
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You never have said what amp you are using. If it is an older 'vintage' amp of the 50's, then that may be the problem. Too little headroom for input.
A couple of other obvious things to check that can cause your problems: 1) Junk or trash around the speaker area (or if it's metal, may be stuck to magnet so that in can interfere with movement of the cone; and 2) on older 15" speakers, the cone can take a 'droop' or warp that can change gap during travel, causing a static or breakup. Simple fix is to remount speaker with a 90 or 180 deg rotation.
Thanx,
Jim |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 29 Sep 2012 9:51 am
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| Are you using a buffer amp? If so, please read Brad Sarno's comments ---> Click Here |
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Michael Hummel
From:
Ottawa, Ontario, Canada
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Posted 1 Oct 2012 2:14 pm
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Thanks to everyone for some great advice. Sorry for the delay -- I was off on a mini-vacation for the last 5 days to see some old friends. They all think I am crazy trying to learn the pedal steel!
I will try all of the suggestions posted and see what is going on, and report back. Might take a few days as I have band rehearsal tomorrow night, and we have some new tunes to learn!
Cheers,
Mike
_________________
MSA Classic 5+4
Too many 6-strings and amps to list |
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Michael Hummel
From:
Ottawa, Ontario, Canada
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Posted 4 Nov 2012 8:39 am
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I've been working at this for some time now. Yesterday I had a bit of a revelation.
COMPLETELY UNPLUGGED, just listening to the guitar all by itself...I can hear a buzzy, crackly distortion kind of sound on either neck. If I play all the open strings loudly, I don't hear it. With the steel on just about any fret, I hear it.
I've tried using lots of pressure on the steel, thinking that maybe I wasn't making good string contact. I put my hand underneath, thinking that maybe the pull rods or something mechanical was vibrating.
I'm using a very high-quality BJs bar with no obvious signs of oxidation or gunk. Can this be the result of slightly old strings (they are maybe 3 to 4 months old with not that much playing time)?
I'm baffled as to what is causing this sound, but it seems to me that if the guitar itself is producing some sort of undesirable noise, it is just being transmitted to the pickups and that is what I am hearing out of the amplifier.
I hate to think this beautiful old Sho-Bud is disintegrating or something...
Mike
_________________
MSA Classic 5+4
Too many 6-strings and amps to list |
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Lane Gray
From:
Topeka, KS
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Posted 4 Nov 2012 9:14 am
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Try new strings. A rust spot will do that
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects |
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Jim Bates
From:
Alvin, Texas, USA
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Posted 4 Nov 2012 10:13 am
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Do you have a loose fretboard? Are the pickups loose in the mounts? Can you tell whihc end the crackling is? Is there a loose tuning key button? or shaft?
Good luck being the detective.
Thanx,
Jim |
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Joseph Meditz
From:
Sierra Vista, AZ
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Posted 4 Nov 2012 10:28 am
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| Michael Hummel wrote: |
| COMPLETELY UNPLUGGED, just listening to the guitar all by itself...I can hear a buzzy, crackly distortion kind of sound on either neck. If I play all the open strings loudly, I don't hear it. With the steel on just about any fret, I hear it. |
The distortion may be from a buzz coming from the back of the bar, i.e., on the roller nut side, that comes from insufficient damping. With the guitar unplugged, make sure you are really damping the strings to the left of the bar with your left hand. |
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b0b
From:
Cloverdale, CA, USA
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Greg Cutshaw
From:
Corry, PA, USA
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Posted 4 Nov 2012 11:13 am
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See if there are any grooves worn into the changer! Also really old strings will buzz if they've worn flat spots into the bottom of them. ALL of the pedal steels I have owned have had some degree of buzzing on certain strings. It's usually a bit worse when the strings are barred.
Greg |
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Michael Hummel
From:
Ottawa, Ontario, Canada
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Posted 4 Nov 2012 1:15 pm
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Thanks for all of the inputs. I've spent a while doing some detective work.
The legs are tight. The pickups are tight. I don't hear any noise from the rollers at the nut. The buzz seems to be coming directly from the changer area, on both necks. Although it's hard to do, I've tried playing a full chord with the steel, and then putting my hand underneath to damp all the mechanisms and the changer area -- doesn't seem to help.
I have noticed a bit of wear on the changer area where the string wraps around, especially on the third string. I wonder if I need the whole changer rebuilt?
This wouldn't bother me too much except that some of the buzz gets picked up by the pickup (I guess that's why they call it a "pickup") and the amplified sound isn't quite as pristine as I would like.
Mike
_________________
MSA Classic 5+4
Too many 6-strings and amps to list |
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John Billings
From:
Ohio, USA
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Posted 4 Nov 2012 2:30 pm
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"from the changer area, on both necks."
That makes me think it's not coming from the changer finger that has a bit of a groove, although you do want to fix that. How about folding up a towel, and putting it on each neck in turn. from above the roller nutz to beyond the changer. You could also put a piece of soft foam, or something, woven around the pull rods. See if that narrows it down.??????
Edited to add, are there any rods that seem loose. Can you pull any of them back and forth without "changing" the changer? I'm a ShoBud guy, so I'm not familiar with this make of guitar.Just shooting in the dark,,,,,,,,,, |
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Frank Montmarquet
From:
The North Coast, New York, USA
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Michael Hummel
From:
Ottawa, Ontario, Canada
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Posted 4 Nov 2012 3:25 pm
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John:
It *is* a Sho-Bud...I'm hoping fellows like you DO know what is going on.
I will try the spring thing later tonight.
Mike
_________________
MSA Classic 5+4
Too many 6-strings and amps to list |
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b0b
From:
Cloverdale, CA, USA
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Posted 6 Nov 2012 8:27 am
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I suspect flat spots on the top of the changer fingers. The curve on the fingers needs to be maintained about once a decade with very fine grain sandpaper, followed by a good polishing.
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Michael Hummel
From:
Ottawa, Ontario, Canada
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Posted 6 Nov 2012 8:54 am
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Bob:
Finally something that makes sense. I've checked springs, rods, legs, rollers.
Is that a job I dare try myself? I'm betting that's never been done on this 35 year-old guitar. Maybe I should take it to Al Brisco for an overhaul.
Mike
_________________
MSA Classic 5+4
Too many 6-strings and amps to list |
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John Billings
From:
Ohio, USA
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Posted 6 Nov 2012 9:14 am
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Oops! Sorry. I had been reading on a Marlin thread, and got lost!
Flat spots, or wear grooves, usually occur only under the strings. Usually, but I suppose not always. So,,, loosen the strings, and slide them over off center on the fingers. Then tune them back up. The string spacing etc., will be messed up, but that doesn't matter, as this is just a test to determine if the fingers have been flat-spotted or worn. |
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