Help!! Oh No!! Amp Farting...

Discussion in 'Amps and Cabs [BG]' started by jokerjkny, May 4, 2002.

  1. jokerjkny


    Jan 19, 2002
    NY / NJ / PA
    Hey all,

    i sold my smaller older stuff, and just got a Demeter VTBP-201s and Stewart World 600. Problem is, using my Elrick 5 and MTD 4 strings, i cant seem to get the Demeter's volume past 9 o'clock without the low B and even E farting out on my Bergantino HT112. the onboard EQ's are flat. the stewart's set in bridged mode and halfway up. i was running into the passive jack, and also tried the active jack, but couldnt nudge the volume past 10 or 11 o'clock.

    With my trusty EA iAMP350, i can crank it up ok, and its all good. with a friend's Aguilar DB359, its ok, and no farting. just fine.

    thinking it was the stewart, i went to a store to get a Peavey DPC1400x and it was ok at first, but later, the farting came back, and i could no longer set the Demeter past 9 o'clock.

    at first i thought it was the Demeter, but later, when trying another friend's DB680 with the Stewart, the farting came back. ***!?!?

    the Peavey seems to be all good.

    what da dilly, yo? is it a bad tube? or just a bad preamp, power amp, speaker? it seems like i cant get alot of headroom from my new setup. Help!
  2. chucko58


    Jan 17, 2002
    Silicon Valley, CA, USA
    I paid for all my gear myself. Well, me and MasterCard.
    It could be a gain staging issue. Have you tried turning up the gain on the power amp and rolling back the preamp volume?

    I have noticed with my own rack rig (highly modified Carvin PB-15 feeding a QSC RMX1850HD) that the preamp's Gain control goes a lot further than I need it to! If I turn it past 10 o'clock with the bass's volume full up, any hard playing will cause clipping in the preamp.

    My low B and E strings seem to produce a lot more signal than the rest, judging by the lights on my gear. Even with a flat frequency response (which I've verified is really flat).

    Add any amount of bass boost and it's easy to imagine demanding more than your amp can deliver.
  3. Pre EB

    Pre EB

    Mar 15, 2002
    Denton, Tx
    OK I'm not sure if this question relates, but I'm gonna ask again. I have noticed a big difference in volume in the same cab (Boogie 210) between my Hartke 2000 head and my Pre/ Power amp rig. The Hartke, pushing 120 watts at 8ohms, seems louder than my rack rig that is putting 270 watts into 8ohms. There is no comparison in sound, the Hartke sounds like a Pinto with a gastrointestinal problem and my rack like a Mercedes on super, but shouldn't the Mercedes easily out run a friggin Pinto? Maybe the added headroom extends the lower frequencies to the point of making me afraid that I'll blow the speakers......I don't know. Any thoughts? Oh yeah, I've set the gain on the pre at 12 o'clock and played with the input sensitivity on the power amp but it is still louder than the 2000 with everything at 12.
  4. Pre EB

    Pre EB

    Mar 15, 2002
    Denton, Tx
    sorry! the last sentence should've said that the Hartke is louder with everything set at 12 o'clock. I'm tired and I hope you guys got the meat of my question, But I hope I'm not stepping on toes here. Maybe it's kind of the same thing as Jokerjkny's problem with his amp?
  5. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY

    I think that CHILD'SPLAY58 has the answer with the gain-staging problem. I've been running my Euphonic CXL112 with a Clarus, and have been getting some farting from my new Smith 6 string. bottom line is I think that my onboard pre is overdriving the Clarus pre when I have the volume on the bass all the way up...same thing happens with my DB when I turn up my trinity pre too far on loud gigs. My first thought was that is was the EA cab, kinda like "Oh man, I just paid alla that money for this thing and how it's FARTING???"

    I'm betting that when my EA iamp750 gets here, I'll be able to control the gain staging a lot better. Have you tried boosting the crap out of your power amp and cutting down the pre?
  6. jokerjkny


    Jan 19, 2002
    NY / NJ / PA
    i think i figured it out...

    like chris pointed out with his bass, my bass was slammin' the input pretty hard too. so i lowered the internal gain trim on my bass onboard EQ. i, too, was bummed out thinking, i spent all this dough on terrific gear only to have it fart in my face. :(

    FYI, just today at my sunday night gig, my Aguilar GS112 handled the demeter pre pretty nicely. I cranked the demeter's volume, and it produced no perceptible buzzing or farting, whatsoever! actually, My Elrick, Demeter, Stewart, Aguilar setup was as smoooooooth as buttah!!! my goodness, the tone was inspiring to say the least.

    After seeing the Aguilar handle the demeter prob easily, i came to some conclusions after doing a little experiment. i kept the power amp volume low, and cranked the demeter's volume. result? i'd get farting, so i immediately assumed it was the Demeter slamming the power amp's input, since the power amp could no way make the cab buzz out at such a low volume. but cause my Aguilar GS112 handled everything ok at all volumes, loud or soft, now, i'm suspecting the Bergie is to blame. i'm gonna take it to Rudy's music and try out the rig thru their Bergie HT112's, and see if my cab needs a trip back to Massachusetts.

    moral of this story? dont think you've know the answer until after, you've checked all your parameters.

    oh yea, and Chris, good luck debugging your system. with enough patience, i'm sure you'll be cookin' with your new setup soon! :D :D
  7. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY
    I think you may have a line on things with what you posted. I doubt you have this problem since you've been a dedicated Slabber way longer than me, but at the moment I have a severe case of the ACTIVE BASS BLUES: My Smith is the first active plank I've ever owned, and it puts out a pretty hot signal. I always use it on doubling gigs, and always pick it up right after playing DB in the middle of a, not only is my preamp slamming the Clarus preamp, but my fingers are still slamming the strings...I used to (gasp) use a pick on a few tunes on my passive plank on wedding gigs back in the day, and I remember that too much force on the strings can also cause speaker farting. So, while I am quite sure that a pick will never touch my Smith, I've still got another "stage" of potential trouble to troubleshoot - I notice that when I lighten my touch, the farting goes away again...but then I still need more volume. I'll figure this out, but not until I get an amp with more headroom.

    Have you tried your Bergie with your iamp? How does it do?
  8. thrash_jazz


    Jan 11, 2002
    Ottawa, Ontario, Canada
    Artist: JAF Basses, Circle K Strings
    I used to have a similar problem back in the days when my poor old 150-watt B3 was stacked up against (pun intended) two 4x12 guitar cabinets. Needless to say, the farting was worse than the worst case of GAS... As mentioned, one way to help stop this (assuming an active bass) is to crank the master volume to full and adjust the gain on the amp and/or bass from zero upward. This way, you're controlling the "heat" of the signal, as opposed to pushing the amp too hard from the beginning.

    Another thing that worked well for me was my SansAmp BDDI... the only problem there is that you're at the mercy of the monitors, which may or may not suck. I believe the DI option to be a valid one, though. Any thoughts?
  9. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    So you've got the gains set at 12? Adjust them. That's why there are knobs.

    You'll find you can get louder (a little more than 3 dB) with the higher-power setup before it clips than with the lower one.
  10. jokerjkny


    Jan 19, 2002
    NY / NJ / PA

    bet i can tell you're a planker by the splinters in zee fingers. :D

    but yea, my rig for a while was my Bergie with my trusty old iAMP350, and it was pretty nice. smooth clear and clean. woulda kept it, until i got a taste of some Demeter action. Wooo Hoo... when i get the farting under control, the tone is waaay sweeter and deeper. fortunately, made letting go fo the iAMP all the more easier, tho still hard. still, it was a good rig, and a rig that was loyal.

    here's an old pic: