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light show from cabinet ?

Discussion in 'Amps and Cabs [BG]' started by Joseph Sheldon, Dec 15, 2002.


  1. I don't know if there has been threads already on this subject or not but here goes. Tonight at band practice I was playing a line thats got a pop on the A on the g string. The singer in the band said after a song we are working on " Dude some light keeps going on when you nail that high note, dude your 10's look like high beems". I'm pushing an Ampeg B4/10HLF and I think it has a bulb on the tweeter crossover for protection and I'm onlt guessing when it starts to clip the light bulb will light up. My setting on the tweeter is half way. You can only have off or half or full. I turned the highs down on my crossover on my M-pulse 360 and it stopped. My questions are : Is that what was lighting up my cab? : Should I turn my tweeter up on full ? : What else can I do to keep the thing from getting close to blowing ?. I don't think I was playing to loud my master gain was on half and the pre was on a third. Of course I never think I'm to loud but this is a matter of taste. Oh yeh I wasn't seeing things all of us play clean if you know what I mean! Thanks for any constructive feedback.:)
     
  2. jobu3

    jobu3 Artist formerly known as Big Joe

    Feb 17, 2002
    Mountain Top, PA
    i had an acme where the same thing happened when it was being used by another bassist. it looked like a strobe light going off. to remedy, i'd either pop a little lighter or back off the tweeter a little... i don't think it really has anything to do with clipping of any sort, i think it's more overpowering the horn than anything...
     
  3. Some cabs have a small light bulb in the horn circuit to soak up extra power that might otherwise blow the horn. When the bulb is flickering on and off it is working. If however your horn quits working, the bulb has probably blown. If you don't have access to a new bulb you can usually get replacements at an auto parts store. They use the same type of bulb as the dome light in your car.
     
  4. lneal

    lneal

    Apr 12, 2002
    Lee County, Alabama
    Tighten up on that compressor/limiter a bit if you have one. If you don't, get one! They are great for keeping those transients under control when popping.
     
  5. jobu3

    jobu3 Artist formerly known as Big Joe

    Feb 17, 2002
    Mountain Top, PA
    they usually use standard 1157 lights if i'm not mistaken...
     
  6. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    You're not clipping yet but the light lets you know when you're getting close.

    A sure fire way to ensure you don't clip is to run the PRE as low as possible. Run the POST at full ball if you have to, but keep the PRE low.

    Any sound engineer will back this up - Clipping usually always occurs in the input stage of the preamp. If you set your PRE to 1 or 2, it's virtually impossible to clip. You can still get the globe to light up but you won't blow anything.
     
  7. jobu3

    jobu3 Artist formerly known as Big Joe

    Feb 17, 2002
    Mountain Top, PA
    yes, but you can still blow it if the treble is set too high, if the master volume is too high, if your tone/treble knob on the bass is too high, your horn is set to high along with the previous factors, or if you slap and esp. pop real hard. while a clipped signal will surely blow out your horn (or its protective bulb) these circuits are not designed to blow just when you clip your power amp or preamp other things may cause it as well. whenever it gets over loaded regardless of how it's gonna light up and blow out...
     
  8. jobu3

    jobu3 Artist formerly known as Big Joe

    Feb 17, 2002
    Mountain Top, PA
    besides, clipping in the poweramp would give a much worse outcome, so i wouldn't try running the master volume at full blast. this can be especially dangerous when boosting the low frequencies. bye-bye speakers (and light bulb :rolleyes: ) and possibly your amp too...
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I think you've missed my point FNA4. I'm trying to explain how to AVOID CLIPPING. Clipping will definitely fry speakers and horns. I have never blown a speaker or horn in 15 years of playing despite being in some seriously loud bands - and I'm amazed that so many people do.

    When U say "Master Volume" I'm not sure if your mean PRE or POST gain. Run your PRE gain too high and you will increase the chances of clipping.
     
  10. Just run the B4 like the manual states. I'm gonna guess that it says to turn the pre until the red LED just starts to flicker. Then set volume w/ the master volume.

    If you had a pre/power setup, then you could stick a compressor/limiter in between them. But this isn't the case with your setup.

    On my SVP-pro, I adjust pregain until just flickering. Then shape the sound w/ the EQ'ing, and then run the carvin FET900 at about 1/2 of gain. It's a old piece of crud lol. Then adjust volume with the master volume on the SVP.

    Don't control the volume level with your pregain. Your tone will hate you for it. Pick a region that's below input clip and makes things sound alive.
     
  11. Fuzzbass

    Fuzzbass P5 with overdrive Supporting Member

    Hang on, guys... the light in question is inside the cabinet, correct? I believe Greybeard is right that when it's blinking it's simply soaking up excess level, regardless of whether the wave is clean, clipped, or in between.
     
  12. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    That's what I thought too Fuzzbass. But he threw me a bit when he said he wasn't playing loud. I guess everyone has a different definition of what "loud" is but.......
     
  13. jobu3

    jobu3 Artist formerly known as Big Joe

    Feb 17, 2002
    Mountain Top, PA
    i was agreeing with greybeard too in that it just takes in whatever overloads the circuit to the horn... sorry about any misunderstanding.

    and yes pete, loudness is completely subjective. if my old guitarist could hear a bass in the mix it's too loud and he was threatened! :rolleyes: ;)

    happy holidays all!!!
     
  14. Thanks for the feedback. I had band on the 21st. And my Mesa has a great on board compressor I raised the thresh. a little turned the highs down just a bit and she is clean as a wistle. No light show any more. By the way I always put my master gain a little more than half and the pre is only at 1/4 I love a clean tight punchy sound! I wonder if I'm getting any warmth out of the 12AX7 in the pre. I'm starting to think by keeping the pre so low I'm not heating the tube up at all, at least not enough to utilize the "tube" sound that my Mesa can produce? I know this is another topic.