Modulus + GK = fart?

Discussion in 'Amps [BG]' started by Axxis, Jan 5, 2013.


  1. Axxis

    Axxis

    Joined:
    Mar 8, 2011
    Location:
    Oslo, Norway
    Hey.

    I own a Gallien Krueger 1001RB-II with two GK Neo 212 cabs.
    I´ve owned this for a long time.

    My main bass is a Modulus Flea with LP pickup and OBP-1 18V preamp.

    The setup has been working really great the last year, gigged a lot with it and played a lot with it. At the band practice today I got an awful farting sound when played at higher volumes. It`s a nice sound as long as I am keeping the volume under 9 O´clock. All the EQ are 12 O´clock and boost and woofer is at a very low stage. If Im play any louder it beginning to fart.

    I´ve tried another cable, change the batteries in my Modulus and no difference.

    I´ve tried an EBS 350 amp on the cabs and it´s a lot better, but the amp is a lot less powerful. I also tried my GK 1001 on a EBS cab and its awful.

    It´s so hard to troubleshoot it, and I need some help from you guys. Is it possible that my amp is not working, but cabs do?
  2. ale29

    ale29

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    Crank the Woofer knob, adjust the boost to taste and set Volume as high as you can without getting unpleasing distortion (even 9 o'clock is fine if needed)
    If you used this very same setup in the past without problems, it just may be that the battery for the OBP electronics is dying.
  3. CL400Peavey

    CL400Peavey Supporting Member

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    Get a second matching 212.
  4. AdamR

    AdamR Supporting Member

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    Hes running two 212's al ready, Maybe to much bass ? try turning the eq down.
  5. christw

    christw Get low!

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    Do you use the 5 string switch or contour on the GK? Both will suck up all of your useful tone and headroom quickly IMO. If you're boosting bass on the OBP-3 it can have the same effect.

    edit: Then again, if things have been consistent all year, I don't see any of these being the issue.
  6. Razman

    Razman Supporting Member

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    Orange Park, FL
    Battery good in the preamp?
  7. Bassmec

    Bassmec

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    I would be thinking that the LP pickup might be overdriving the output of the OB3 if the bass was boosted by much and if the volume control on the bass was dimed.
    Perhaps if you tried to see where the distortion was occurring by changing you ratio of gains and frequency boosts.
    IE open up the master volume and reduce levels at the bass guitar volume and or the amp gain to see if your headroom improves if not
    You will need to buy more speakers to meet your volume and VLF goals.
    :bassist:
  8. Axxis

    Axxis

    Joined:
    Mar 8, 2011
    Location:
    Oslo, Norway
    Hey.

    LP pickup has been there all the time
    It's a OBP-1 not 3.


    I've tested it more this morning and found out this:


    Batteries are completely new

    I can turn of bass on both the bass and amp, but no change.

    If I turn the volume down on the bass the distortion goes away, but that is not an option for me.

    When I'm just playing the E string while turning the volume up on the amp, the sound is good to 9 o`clock, but as soon as I go past that the volume stays the same all the way to full twist on the knob, but the distortion gets worse. So the volume won't get any louder than to 9 O`clock.
  9. Kenner

    Kenner

    Joined:
    Sep 1, 2007
    Location:
    The Mini of Apolis........
    ...for giggles...try
    Volume - 12
    Contour - 2
    Presence - 10
    Treble - 2
    Mid H - 12
    Low mid - 1
    bass - 12
    Boost - 1
    Tweeter 10
    Woofer - anywhere you wanna
    use the 5 string/ rather 4 string tone switch

    This is what I use for settings (along with other toys in the chain) with an Alembic

    it is into a 700RB/112 combo into a 1001RB/210 bottom without the 1001RB (just an extention cab) at 4ohms.... screams loud....

    give it a shot....
  10. Codger

    Codger Supporting Member

    Joined:
    Apr 13, 2008
    * Bass into GK 1001 into dual 2x10s farts bad.
    * Bass into EBS amp into dual 2x10s farts but not so bad.
    * Bass into GK 1001 into EBS cab farts bad.

    That the GK1001 farts with both cabs seems to clear up the speakers as the problem, so could be GK 1001 or bass.

    That the EBS amp farts also seems to clear the GK 1001 as the problem, so it could be the bass.

    I'd look at the bass. Try it with a different one and crank it up.
  11. Axxis

    Axxis

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    Location:
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    I am playing with a Fender MIA Jazz std.
    It farts here aswell, but im able to get a higher volume before it starts. And, its not as bad, but still...
  12. Axxis

    Axxis

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    When playing some of the higher strings and over 12th fret the GK farts at 9 o'clock, but playing the EBS amp at same volume (almost maxed out) it playes without any distortion. Starting to think its my amp.
  13. Bassmec

    Bassmec

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    I think you are running out of X max on the loudspeakers as that's what I think of as farting as a separate sound from amp clipping.
    My Wilkes frankenray sliding pickup 5 string has a Nordstrand MM 5.2 pickup which wont be that different in its VLF output to your Lane Poor pickup tuned to B.
    The std jazz bass is not going to fart out the speakers half as much because it has half the very low frequency energy.
    I don't like to run out of headroom in my onboard pre amp, I like to abuse a tube pre amp for any filth I require.:bassist:
  14. wvbass

    wvbass Supporting Member

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    IME, and supported by the block diagrams, it is possible to overdrive the input of a GK with a high output bass, regardless of knob settings.
  15. Axxis

    Axxis

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    Yeah, but disrtion comes with the Jazz aswell
  16. 1958Bassman

    1958Bassman

    Joined:
    Oct 20, 2007
    I would bet that the port and cabinet are tuned too close to the lowest notes of the bass and/or the power handling capability of the driver in that specific cabinet isn't high enough to use that amp.

    This is from the GK manual- "Frequency Resp. (-3dB): 53 Hz to 19 kHz" and if you're using a Flea 5, it may be the cause. It's hard enough to make high power and small ported cabinets work, but adding low frequency extension makes it even harder to do. If it's the Flea 4 and with 18dB of boost @40Hz, you're going to kill your drivers. 18dB of boost is a helluva lot- almost 1000x the level of 0dB. If the amp is putting out 2W, the 18dB of boost is making it send far too much bass to the cabinet, which is not what it's designed for.

    Try it with the Low cut ON, then work with the bass control- the low cut is made to reduce this kind of problem and the bass control is centered at 60Hz but still affects frequencies an octave above and below.

    Here's a link to an Eminence BassLite S2012 driver-Make note of this at the top "Displacement Limited to 125 Watts."

    The driver is rated for 600QWRMS but not in a cabinet of the size used for the graph.

    http://www.eminence.com/pdf/Basslite_S2012_cab.pdf

    I posted this before and, not that I'm the guy at the top of the mountain who knows everything, but I have worked with audio equipment for over 35 years. The one thing that makes equipment live a long, happy life is, DON'T TRY TO MAKE IT DO THINGS IT'S WASN'T DESIGNED FOR, OR CAN'T PHYSICALLY DO. The limitations of the equipment MUST be known, if the system can be designed, at all. If this step is skipped, it's not 'designing' a system, it's 'assembling' a system.

    Look at a well-designed PA system- the signal sent to each type of driver is ONLY within the usable range of that type of driver. If it's being used in an outdoor space, they need more subwoofers because there are no/fewer boundaries to use for reinforcing the low end. More drivers AND more power. Why? Because the frequencies needed are A) harder for humans to hear, B) harder to achieve under any circumstances and C) the best ways to get more SPL is by using more power AND more cone area, not one or the other.
  17. Axxis

    Axxis

    Joined:
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    Location:
    Oslo, Norway
    Thanks for the long answer. I am not good with electronics, but i have some questions for you.
    The 18db boost, is that from the 18V pre?
    Its a flea 4.
    I have these same issues on a standard Jazz Bass. There is no problems when using a different amp.

    If we forget the flea bass (it works great on any other amp ive tried, and worked great with my GK since i bought it a year ago), and focus on the Jazz. How come it still distort? When yousing a 300w EBS on my cabs theres no problem.

    Is there any common failure with an amp that can cause these distortions?
  18. B-string

    B-string Supporting Member

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    Location:
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    I suppose you could have damaged the FETs in the input with the Flea 4. There is no way to prevent (on the amp head) a overly hot signal from hitting the front end.
  19. 1958Bassman

    1958Bassman

    Joined:
    Oct 20, 2007
    The 18dB boost is from the preamp. Remove/bypass the preamp and I suspect you'll also eliminate the problem.

    Think of the input section as the ceiling in your bedroom and the signal as you jumping on your matress. The more you push off with your legs, the less headroom you have before hitting the ceiling. Replace the original mattress with one that's more "springy", and you'll bump your head on the ceiling. Going through the ceiling is like causing distortion- great if you want it, but not if you don't. The easy ways to reduce the chance of bumping your head are A) lower the mattress and B) use a less springy mattress. The springy mattress is like having something "extra", to help you go higher and the preamp making the signal louder is doing the same thing- your signal is going through the ceiling. The problem is that the boost is so much the amp (I suspect the speakers more than the amp, but it could easily be both) can't handle it without sounding bad.

    If your other bass causes the same thing, it could be that the speakers and their cabinet can't handle that amount of power. The 1001 is a lot of power and the speakers may not have been able to handle it without damage. The damage doesn't always happen immediately, either. They get to a certain point and you can hear it, when you couldn't before. the 300W amp isn't able to drive the speakers as hard, so you don't hear it.

    Are these speakers under warranty? If not, carefully remove one of the 12" speakers and look at the edge. If you see that it's torn/ripped or has any kind of hole, it needs to be repaired. There's a piece that may be orange, tan, gray or black, where the angle of the voice coil stops. This usually has a surface that's similar to vvvvvvv and looks like cloth. If that's loose or has any kind of hole, it's damaged. Either or both of these problems will cause the sound you described.
  20. murphy

    murphy

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    Very funny analogy

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