1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

question on amp heads.................

Discussion in 'Amps and Cabs [BG]' started by Rob Terry, Nov 6, 2003.

  1. Hi all and thanks for reading.....

    1. I have a Ampeg B-2R amp head and a 15SVT Cab. When my gain is at 12 and master is about 10 I get clip and limit. Why would this happen if the cab still sounds fine and it should be able to put out a lot more power?

    2. Is this a cab or head problem?

    3. What exactly is getting hurt and what does this mean? What am I doing wrong?

    4. As far as I know my head and cab should have no problem at this volume. What should I do to fix it, what causes this problem?

    Thanks in advance. HELP!!!!!!!!
  2. Hmmm. Have you tried turning your gain down and master up?
  3. actually I haven't, I tried the oppisite. I will have to try that along with someone told me I might need to turn the bass down and the low mids up for more balance.
  4. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    According to the manual, the PEAK light comes on when the signal into the preamp is too hot. The LIMIT light comes on if the power amp is approaching the clipping point.

    To get the clip light to shut off, reduce the setting of the gain knob or cut back extreme EQ boosts (see below).

    If the limit light is staying on most of the time, you could turn the limiter off to get a bit more volume but you may also get distortion.

    Both lights on means you are driving the amp full blast and it's as loud as it's going to get.

    What are your EQ settings? If you are boosting the lows excessively you will get those lights to come on really quickly even though overall volume seems low.

    Try this:

    1. Set ALL EQ knobs to 12:00

    2. Turn OFF the graphic EQ

    Now see how loud the amp gets before the lights come on.
  5. I do have a real bassy thing going. Maybe if I higer the low mid, lower the bass and mess with the gain This will work out.

    Why do the knobs turn so much if it maxes there?
  6. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    The rule of thumb for wattage is if the signal increases by 3 dB you need double the wattage to reproduce it. OK?

    Now, the bass EQ knob on you amp probably boosts 10-12 db, the graphic EQ slider also can boost that much, so we are talking a potential of up to 24 dB boost. OK?

    A 24 dB boost requires the amp to put out 256 times as much wattage! So if you needed a mere 10 watts with the EQ set flat, with a 24 dB boost you would need over 2500 watts :eek: You can see where this heading, I hope.

    So what happens is you drive both the preamp and power amp into clipping only at the very lowest frequencies. This causes the limiter to kick in to clamp the volume for ALL frequencies. Because we can't hear distortion in low frequencies easily, the amp doesn't sound distorted at all just not very loud.

    However, there is good news here. The louder you play, the less bass boost you need to use...and if you reduce the bass boost then the amp will be able to play louder.

    So turn down your EQ boosts. When EQing it is always better to CUT what you don't want than BOOST what you do want.
  7. Tim Cole

    Tim Cole Supporting Member

    Jun 12, 2002
    Findlay, Ohio
    Moved, quite obviously the wrong forum.
  8. Stephen Soto

    Stephen Soto

    Oct 12, 2003
    If you turn the master up, and the gain down it won't (shouldn't) clip. Because if the master is down, say you had a 1000 watt amp... If the master was at half, the cab think it was putting out a max of 500.

    Correct me if i'm wrong ;) :oops:
  9. Sorry, you're wrong.;) :D

    There is no consistent relationship between the position of the master knob and how much power you're putting out. Putting the master volume on half does not equate to 50% power.
  10. Stephen Soto

    Stephen Soto

    Oct 12, 2003
    Well, let me state it differently then. Wouldn't the amp clip more if the gain was maxed and the master was at half or whatever??:oops:
  11. Almost all bass amps today are realy a pre-amp amp combo

    All the knobs on bass amp are controlling the pre-amp section, none of them controll the actual amplifier section.

    The gain is how hard the pre-amp listens to the bass.
    the Vol is how loudly the preamp talks to the amp.

    If the gain is too high you will drive the preamp to distortion. This kind of distortion is ok for your speakers, its not great but its ok to a point.
    This is the gain light turning on.

    If the vol is too high the amp will be forced in to distortion. This is the realy bad form of distortion.
    This is the amp limit light turning on.

    Now it is possible for the pre-amp distortion to cause the amp to distort by sending too strong a signal to the amp.
    This is what happens when you see both the gain and amp limit lights turn on.

    The amplifier section simply takes a signal and magnifies it. The amp has a fixed amount of power that it can use (how many wats) if the signal causes the amp to try and magnify the signal beyond that set amount the amp will clip.

    hope this helps