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stepping on the "Clipping debate" landmine...

Discussion in 'Amps and Cabs [BG]' started by MisterSkimpy, Jan 27, 2006.


  1. MisterSkimpy

    MisterSkimpy

    Dec 21, 2004
    I've recently purchased an Ampeg 410 with B2RE head. This is an upgrade from my Crate BX100 (is there a stronger word than upgrade????). Since I now have equipment that I'm concerned about taking care of, I'm trying to wrap my head around this clipping issue. After reading the clipping damage thread, my previously-mentioned head almost exploded.

    Does anyone have recommendations for a practical way to approach using my cab/adjusting my levels to both provide plenty of sound and ensure I don't damage my speakers? My handy B2RE manual says to adjust levels to where a "strong note" gives me the red clipping light, and to have the limiter engaged. So fine, I'm doing that. But based on previous threads here at talkbass, as well as the knowledge that the light means I'm going somewhat out of my cab's range, I'm getting picky about not hurting the biggest purchase of my life.

    So to simplify; how much red light is a sign that I need to back off/turn down? I know that question has no definitive answer, but really I'm just looking for advice on how to get a grip on my cab's range/capability in a manner that doesn't involve a big pop and lots of smoke:p

    Thanks!
     
    Oddly likes this.
  2. Fuzzbass

    Fuzzbass P5 with overdrive Supporting Member

    IMO your main concern shouldn't be clipping, it should be sending too much power to your speakers (clipped or not): that's the real danger. My hunch is that the amp is a good match for the cab, and there's not much danger of blowing anything up... but I don't recall the specs of that gear offhand.
     
  3. Eric Cioe

    Eric Cioe

    Jun 4, 2001
    Missoula, MT
    I usually don't let my clipping light come on, but if it does once in a while, I don't worry too hard about it. My GK head seems to like being set a little before the clipping point.

    Also, the clipping light has nothing to do with your cab. All it means is that your bass is overpowering the preamp section of your amp. I think those are called square waves, and they usually don't sound good, although distortion is more or less the same thing. The limiter is probably a good idea, though not necessary.

    Remember - the clipping light has nothing to do with your cabinet. It only has to do with your preamp section of your head. You're not going to explode a cabinet by overdriving the preamp a bit. Hope that helps.
     
  4. Herman

    Herman

    Dec 25, 2005
    Lynchburg, VA
    Which 4X10 cab do you have? Different Ampeg 4X10 models have different impedance and power handling specs.

    To clarify your statment:

    From the B2RE manual:

    "9. LIMITER: The B2RE uses an internal
    Optocoupler Limiter to assist in keeping the
    power amplifier’s output “clean” at extreme
    volume levels. (All amplifiers begin to clip
    their output signals as they approach maximum
    output levels, resulting in distortion
    which may damage your speakers.) To
    engage the Limiter, depress the Limit
    switch. Whenever the amplifier is at full
    power, the adjacent Limit LED will flash.

    This is an indication that the limiter is keeping
    peak signals from clipping the output."

    The red light isn't an indication that you're pushing a signal that's out of your cab's range. It's an indication that the amp's internal limiting circuitry is being engaged to avoid sending a clipped signal to your cab - that is, you're trying to drive your amp into clipping but the limiter won't let you do it. What you end up with is a clean signal at the amp's peak output power being sent to your cab. As long as your cab is rated to take program peaks at or above your amp's max output, you should be OK.
     
  5. juan13

    juan13

    Mar 4, 2015
    south america
    I'm very interested if pushing too hard the preamp section, in other words, keeping the red clipping light going on a lot can damage the head itself (not talking about the speakers). Last day i was using a GK mb500 head and some bass player kept the red light going on forever althought the -10 pad was activated it was going on and on (limiter also activated)...can that damage the head?
     
  6. BadExample

    BadExample

    Jan 21, 2016
    IMO overexcursion is the highest risk to a woofer or full range bass speaker.

    Thermal wattage just so happens to _loosely_ track the mechanical limits. This is in my opinon because there is no point in using a more expensive and heavier magnet and high wattage voice coil on a speaker that is made for very minimal excursion.

    The sellers of assembled speaker cabinets rarely offer "up front" much information about what limits you can expect. Sometimes you can dig up more information one way or another.

    I think the most important thing to do is to learn to listen to your speaker warning you that its being pushed beyond the point of sounding good and closer to the point of suffering damage.

    This, I think is a reasonable approach and concurs with what @agedhorse has said on the topic as I understood him and as my bramaged dain recalls. I am not saying he endorses this. Andy is certainly welcome to yell at me if he chooses to read this and I have misunderstood what he has said in the past. Anyway, https://peavey.com/support/technotes/poweramps/HOW_MUCH_POWER.pdf
     
  7. juan13

    juan13

    Mar 4, 2015
    south america
    Anybody can answer to my question? I have seen in a lot of posts how when someone asks it it is automtically left aside.
     
  8. Rick James

    Rick James

    Feb 24, 2007
    Montreal
    No. Clipping can damage tweeters, that's why bass amps often have some method of clipping protection. If you don't have no tweeters you have nothing to worry about, just as guitar players don't. They clip their amps as a matter of fact, but they don't use tweeters.
     
    juan13 likes this.
  9. juan13

    juan13

    Mar 4, 2015
    south america
    thank you!
     
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    While partially true, it would be inaccurate and incomplete not to mention misleading that guitar speakers thermal ratings are derated to account for the additional power (above rated power) that clipping causes. In most bass guitar speakers there is not the same derating applied which means that if you will be clipping the amp, your speakers might be subject to more power than you otherwise might think. It's not the clipping that hurts a woofer, but the additional thermal energy that clipping can deliver.
     
    BadExample and sstillwell like this.
  11. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    There are two LED's that react to signal levels in your amp. One is a peak indicator, located at the input input of the preamp, the other is the limiter indicator in the power amp. They are both a guide related to distortion.

    The peak is set to avoid overdriving the input from your instrument. It is calibrated to flash when the signal is high enough to distort. If you want a clean sound, set the input gain or EQ to minimize flashing. You want to find the right balance so that the input signal is optimally high enough but not so strong that the amp is distorting heavily. The LED provides a visual to supplement what you are hearing. Don't just go by the light, use your ears. If you are driving the input hard, the light will flash. If you like the sound, don't worry about it. Passive and active basses have different signal levels. Actives are usually hotter. Pedals also provide more signal. You adjust the gain using the LED as a guide to best suit the input level.

    The limiter LED is also important. It is telling you that the power amp is being driven hard and the limiter is engaging. The limiter affects the sound and it acts to protect the power amp. Turning down the volume or the low end EQ will prevent the limiter from engaging. Again it depends on the sound that you want. At high levels, when the limit button is in, the LED is going to flash. This is normal and nothing you have to worry about. Use this as a guide for setting the level for the sound that you want. It is telling you how hard you are driving the power amp and that there is some distortion. If you want to avoid distortion, back off the settings. Some distortion is good.

    There is a thermal protection circuit in the output stage that will shut down the amp if there is a problem. It will also shut it down if the line power level is too low. If this happens, be concerned.

    Check out the block diagram at the end of the manual. It illustrates where in the amp these LED's come into play.

    http://www.ampeg.com/pdf/B2re.pdf
     
    Last edited: Oct 22, 2016
  12. BadExample

    BadExample

    Jan 21, 2016
    You may or may not exceed the drivers
    Also a fair chance of exceeding mechanical limits if not listening for speaker distortion. Eq may be your friend, but it can also be the woofers nightmare.

    The pdf I posted covers a lot of this, but expect up to 2 x the rated power of your amp at full clip. Burning the VC you don't hear until there is silence. Beating it to death you can easily hear with a clean signal, but I don't know what to expect with an extremely overdriven (clipped) signal. If I were to do this, I might test with a clean signal at the desired eq., listening for fart out, then go to half that power for full clipping. You would need to be able to measure power output of the amp, because the knobs do not indicate power. But I don't even want to hear a fully clipped SS amp :D

    Edit: as far as amp safety, a continuous square wave is likely to heat it up. Of course you're not doing a continuous wave when you play, but it would be a good idea to monitor the temperature.
     
    Last edited: Oct 22, 2016