Farting? (amp question)

Discussion in 'Amps and Cabs [BG]' started by Mo'Phat, Oct 1, 2003.

  1. I'm stumped. I play a Stingray 4 through a Mesa 400+, Mesa 4x10 and 2x15, and I reach a certain volume to where the clean turns to fart. My guitarist plays a Mesa Dual Rec...loudly.

    I'm looking for that all-important 'suck' button that's engaged...

    Is there a particular eq band that needs to be tweaked? Is there a particular compression setting that needs to be maintained?

    My band plays many shows where the bass rig has to fill the room by itself, and we play a combination of dub/hardcore/hip-hop/rock. My tone (when playing at reasonable levels) is round, punchy, clear as a bell, with a huge ass. It just doesn't translate well when I have to turn up to impact the space.
  2. j_sun23


    Feb 24, 2003
    Baton Rouge LA
    What eq freq does the Mesa have? What about your bass? I bet if you cut a lot of the lowest lows you will take care of your farting prob.

    I used to use an SWR 6x10 and it had "bad gas" :). I grabbed that 30hz slider on my preamp, pulled it all the way down, and problem solved. Experiment with your eq. Extreme eq settings, especially in the lowest end are usually NOT good for your speakers or your sound. 30hz is really felt more than heard. As a matter of fact, you sorta don't hear a big difference in low end eq'ing until about 60-80hz, or at least that's been my experience. Yeah a low B string fundamental is 30hz, so what. If it makes your speaker fart, then what use is it. Same goes for a 4-stringer, in principle at least.
  3. It's a Mesa, so it's got Bright switches on both channels, Bass w/ shift, Treble w/ shift, and Mid (all parametric) and a 7 band graphic eq. I can't for the life of me remember the bands the eq hits.

    As for felt more than heard, it's imperative that my bass be both felt and heard. Is there a way to have both without any sacrifice?
  4. redneck2wild


    Nov 27, 2002
    Memphis, TN
    Do both cabinets sound bad at this loud volume or is it just one cabinet?

    Is it only when you hit the lowest notes?

    Does it sound bad only when you hit the strings hard?

    Chances are either one or both of the cabinets can't handle a certain frequency at a high volume. You could cut the lowest frequency in the graphic EQ (the one to the far left) when you increase your volume.

    If you like the deep lows that the lowest frequencies give and you don't want to cut your lows on the amp there may be other ways to get it.

    If it sounds worse when you hit the lowest notes or when you hit the strings hard, a compressor may help you.
    Digitech has a Bass Compressor pedal that has 2 compressors built in - one for the lows and one for the highs. I have found that it only works well for passive basses. You can get a good deep bass sound with it with the low level turned up.
    There are a number of rack mount compressors on the market. I have a Rane in my rack, a DOD for monitors in our PA and 2 dbx compressors for the Mains and Subs in our PA.

    Another option would be to use something like a BBE processor or an Aphex processor. Both will give you more lows and punch without driving the speaker harder (unless extreme settings are used). The new Aphex pedals have a low tune knob that allows one to dial into a certain frequency.
  5. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    That's not farting, it's tube warmth.

    Seriously, you might be expecting too much from what is ultimately a 300W head. Seems to me, from your stated needs, that you might be better off with a big honkin power amp (over 1000W) so that you'll have the headroom to keep things clean at your stage volume.
  6. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Yeah, that's a tube amp right? Has a bunch of 6550's in it, something like an SVT or a 300PS?

    There may be a flaky cap in your preamp somewhere (like a cathode bypass cap), that can easily contribute to bass farting. How old is the amp? If it's more than a few years old and it hasn't had a cap job, I'd look into that.

    With a tube amp, it's very important to do regular preventive maintenance. Other than the obvious thing (the tubes), caps are at the top of the list.

    Also I'd check the bias on the power tubes, an incorrect or inappropriate bias setting can cause farting. And speaking of tubes, have you checked them lately?

    While I disagree with the gist of ihixulu's first sentence (you can, and often do, have both at the same time), the rest of the post makes sense. If you're looking for lots of clean headroom, then a mondo solid state power amp is what you want. A tube amp of the same power may "sound" louder but at the expense of increased distortion and significantly less clean headroom. So for instance, 300 honest tube watts might equate with about 1000 solid state watts, in terms of what you hear might be approximately the same volume, but the solid state amp will give you headroom and clean dynamics (like transients) that the tube amp won't be able to deliver at that volume level. On the other hand, the tube amp will give you that "tube warmth", so it all kinda depends on the sound you're after.

    But you know, 300 honest tube watts is pretty darn loud. I have a Fender 300 PS that's probably pretty close to your amp in terms of the power it delivers. It's kinda like an old SVT head. My feeling is that this kind of amp is plenty loud for all but the biggest performances. With one of these amps and an 18" speaker (or an 8x10, or whatever combination you prefer), you should be good to go for pretty much any indoor gig except a concert. If 300 honest tube watts isn't enough for you in club situations, then you're probably playing too loud!
  7. bben


    Feb 28, 2002
    Santa Fe, NM
    In addition to the usual suspects already mentioned, including not enough power, I have heard farting from between the rim of the speaker and the cabinet when the speaker mounting bolts had loosened up over time. Worth checking.
  8. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Nope. The price you have to pay is really high wattage and really big speaker cabinets.
  9. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    He's already got the big speaker cabinets - maybe replacing the 400 with a tube preamp and 2kW+ poweramp would do the job.

  10. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Yes, that's a thought. Here's my experience with "being felt" ('cause I have the same concern, my style kinda creates that same need).

    First off, I use 18" EVX-180A speakers, they handle plenty of power and they'll make your pant legs vibrate at 50 yards. You need the big speakers to deliver lots of power "through the ground" to get the ultra low frequencies through the ground from point A to point B. That's why as a bass player you need a lot of power, 'cause most materials become highly absorptive at low frequencies and the dispersion is also a lot higher in that range. So use as much power and as many speakers as you think you need in the low registers (if you see people start to run for the bathroom, you're probably a little too loud).

    Personally I like 15's, especially the BagEnd 15's which are very punchy, but they still don't deliver that earth shaking pant vibrating fundamental that an 18 does. An 18 might not be as punchy, but you really don't hear that below 60 Hz anyway. The primary need is to make the earth move at point B.

    The highs, on the other hand, don't need that kind of power. If you're using a biamp system, you can get away with a lot less power on the high side. In that range, it's more like a guitar amp, with the caveat that since you're competing with a drummer and a couple of guitars, you might need a little more power (but not much more). A couple hundred watts should be plenty in this range. Three hundred is probably too much for most club situations.

    So what you could do, if your preamp has a crossover, is to use your existing power amp for the high end (you can dial it down so it'll be cleaner and you'll have some headroom), and get a mondo solid state power amp to drive your low end sound. Whatever you do, don't use your 10" speakers below 50 Hz, that's an instant source of farting (not to mention blown speakers). Cross them over and use them to deliver your high frequencies, then use the 15's/18's for the bottom end.
  11. Thanks so much for the responses.

    Here's a little more about my predicament: I don't have a crossover in the amp, both cabinets receive pretty much the same power and frequencies. Both cabinets have attenuatable horns, but I've turned the one in the 2x15 down.

    I don't know how old the head is. I bought it off eBay, and don't have any information on tube age. They're all Mesa tubes, however, which leads me to believe the previous owner bought into Mesa's rhetoric about not replacing the tubes with anything other than Mesa tubes, or they were never replaced. This head could very well be 6 years old or more without a tube replacement. However, they are all still glowing as they should be.

    The problem may be my technique, but that CAN'T be the problem, because I won't let it be. I love my technique, and I'm not willing to sacrifice what I do with my hands to compensate for the shortcomings of technology. There are some soft-attack dub parts that have to be loud, and then some funk-slapping parts that I beat down. I'm currently using a Joe Meek MC-2 Optical compressor, but maybe I don't have it set right for how I'm playing. I also use a BBE 462.

    Do I have too much crap in my signal chain? Maybe, but even without it, I get that farty, not-enough-headroom/speakers-are-working-too-hard grunt.

    ps. the sound universally comes from both cabinets.

    pps. the 4x10 is a year old, and the 2x15 is two months old. I'm not looking to trade up or change speakers anytime soon.

    ppps. I think I'm the only one that notices, so...
  12. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I think the general consensus is that's the problem. Try backing off your very lowest lows and boosting your mid bass (i.e. add at 100Hz, remove at 30Hz) and you'll still feel the bass, have more headroom and not need to buy a more powerful amp.

  13. You're running out of power, it's that simple, BUT the amp you have with your speaker cabs should be able to do what you want. It's probably less a case of tubes "age" than it is that the power tubes are crap to begin with. Mesa branded output tubes in the Bass 400+ are either junk Chinese 6L6 copies which are underpowered or Sovtek 5881's which aren't really right for the circuit so they don't develop as much power. Get a good set of JJ Electronics 6L6GC's and have them installed by a tech and you'll think you have whole new amp. Do a search for Mesa Bass 400+ owners that have retubed with better tubes and see what I'm talking about.

    BTW, a tube's glow has NOTHING (well not exactly nothing, but it's not an indicator of tube health) to do with whether it's working or not. All you're seeing is the heater filament. Sometimes it's not even visible AT ALL, but that doesn't mean the tube doesn't work, conversely I have dead, shorted, and even broken tubes that will still light their filaments. The only way to test tubes is to check them on a transconductance tester or have a tech check their performance in the amp.
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