How do I use a limiter knob?

Discussion in 'Amps and Cabs [BG]' started by rabid_granny, Jan 7, 2003.

  1. I was at an audition and got to use an SWR Workingman 4004 head w/4x10 cabinet.

    I noticed there was a limiter knob with a green light that kept flashing. I assumed that meant the power amp was clipping so I had to keep turning down the master volume. It didn't help that the other guitarists were going bananas with the rented Marshall stacks.

    Anyways, my Yorkville amp only has a limiter button which I keep on all the time.

    How do I use a limiter knob? I've never heard of that before. Since I don't own an amp with such a knob, I can't experiment at home.
  2. PollyBass

    PollyBass ******

    Jun 25, 2001
    Shreveport, LA
    AH! The same thing was on a head i used, and was CONFUSED about it the whole time till i asked on here.... lets see if this is right. The green light is FINE... it just shows the tubes, or whatever, are getting some should be fine. but if there was a red led on the head, then THATS the light that shows it's clipping. i always thought the lilght coming on my head was a bad thing,,, but green is good. Someone correct me? i belive i'm right.
  3. This is what I think happens. When the green limiter light comes on it means that the signal is being electronically trimmed back when it reaches a cirtain level. Kinda like something riding herd on your volume peaks for you. The higher you set the limiter knob, the more sensitive the circuit becomes. Most people set them so that they stay off when they are playing normal and kick on when they get over excited. The output of your bass guitar will determine where this point is, so you'll have to adjust the limiter each time you change guitars or adjust the volume on the guitar output. Hope this helps....:D
  4. monkfill


    Jan 1, 2003
    Kansas City
    I don't understand the idea of a VARIABLE limiter. I thought the purpose of the limiter was to keep the amp from clipping. The amp clips when it runs out of headroom. . . It doesn't seem like the point of clipping is adjustable. I want something that will prevent the amp from clipping. I don't want it to stop the amp way short of clipping, because this would prevent the amp from reaching its potential, and I don't want it to allow even the slightest bit of clipping, because that damages speakers and sounds like crap on a solid state amp anyway. I like the limiter on my SWR 350x- its either on or off.
  5. monkfill


    Jan 1, 2003
    Kansas City
    On the 350x, the green limiter LED means the limiter is engaging and is stepping in to protect the speakers from damage. According to SWR, if this light is blinking intermittently, or even lights up and stays lit, that you are safe because the limiter is doing its job. If it stays constantly lit, you probably need more power, but in theory you are safe. The RED LED on the Gain control lights when the preamp is clipping. Since there is no limiter here, you need to back off on the gain so this light doesn't come on. Even with the tube preamp, preamp clipping on the 350x still sounds awful and will damage your speakers.

    Other amps have lights that behave differently, such as the green light that comes on whenever a signal is present.
  6. PollyBass

    PollyBass ******

    Jun 25, 2001
    Shreveport, LA
    ah, thank you.
  7. Shoot, I should have done a search first but I thought this was an odd question.

    There was a red LED but that was for pre-amp clipping. That was off the entire time.

    I noticed that when I turned the limiter knob, the volume level decreased but I can't recall which way I turned it.

    If the limiter knob is turned all the way to ten, does that mean it is allowing the amp to be pushed to the limit?

    Could I have cranked up the master up to get more volume or would the limiter have prevented further volume increases? I was totally confused because I thought 4x10's could compete with a Marshall JCM 900 through 4x12's. I was getting killed out there. I didn't want to damage the rehearsal space's stuff.
  8. Here is the explanation form the 4004 manual (found on the SWR website).

    Variable Limiter Control

    The 4004’s soft knee-type limiter is there to help you protect your power amp from harmful states of operation. The circuit is located after the Master Volume and before the power amplifier, so it’s driven by the Master Volume control. Its threshold (starting point) is preset by the factory so that you can get maximum overall apparent volume without unduly overdriving (or “clipping”) the power amplifier—which, over time, can eventually damage the unit’s internal circuitry, as well as damage speakers connected to your amp.
    Using the control is simple. Turning the Limiter Control clockwise (toward “MAX”) increases the amount of limiting on your signal, while turning it counter-clockwise decreases the amount. When trying to find the highest possible level of power amp operation under clipping, simply use the Master Volume and Limiter Controls together to find: a) The
    highest setting possible on the Master Volume; and b) The lowest possible setting of the Limiter… all while hearing no power amp distortion whatsoever.
  9. So pardon my stupidity, but does this mean the next time I see a limiter knob (I'm so tired of typing "limiter knob" already...) I could just set it at 0 and everything is good? All I'd need to do is turn up the master to the point just before hearing speaker distortion?
  10. BruceWane


    Oct 31, 2002
    Houston, TX
    Ah, well, there you left out one "four".......four 4x10's can compete with a JCM900 through a 4x12...........


    Actually, I'm not exagerating all that much. If you've got a guitar player that is running that kind of rig at it's limit, you'd need some seriously heavy artillery to compete. The curse of low frequencies - it takes a heckuva lot more gear to produce the same db's as that produced in a higher frequency range. In other words, 100 watts of guitar = usually about 1000 watts of bass, although certain tube amps (SVT, 400+) can settle the score pretty well on less wattage (tube compression and such...a whole different discussion).

    At one time I played with a guy who had the classic heavy metal rig - an old Marshall head with two 4x12's. And it was just sacrilege for those knobs to be on anything other than 10. You gotta understand, this was 1983 or so, the height of hair metal (pun!). Metal guitarists DID NOT use little combo amps. I was running 1000 watts bi-amped into two 1x18's and two 1x15/tweeters and could just keep up.
  11. monkfill


    Jan 1, 2003
    Kansas City
    See, I guess I want something a little more idiot proof, like the limiter that is either on or off. You can't always hear potentially damaging distortion when the whole band is going.

    In my mind a limiter is a safety net. Its not a compressor. A limiter should kick in right when its needed, to prevent a clipped signal from hitting the speakers. I don't understand why there is anything to adjust.
  12. Personally, that's what I would do - that's why I think a preset limiter makes more sense.

    However because distortion is frequency dependent, it is theoretically possible that the limit level could be set differently for the same master volume depending upon the EQ settings being used. A fixed limiter would not allow the limit point to be moved, and may in fact limit volume when it is unecessary.

    In any case, I think the correct answer is - if anyone is pushing their rig hard, enough for limiting to be an issue, get a bigger rig.;)
  13. Groovy, now I know how to use the LK. But I'm still a little shocked that a bass using 4x10's can't compete with a guitar with 4x12's.

    It's not my rig - it was the rehearsal space's rig. I would have thought they would have a more balanced set-up. (Why the heck do you need a 4x10 guitar rig in such a tiny rehearsal space anyways???????? :confused: )
  14. RevGroove

    RevGroove Commercial User

    Jul 21, 2002
    Burlington ON Canada
    Manager, Account Services: Long & McQuade Ltd. (Burlington); MTD Kingston Basses International Emerging Artist; Bartolini Electronics Emerging Artist
    Well, the 4004 head only pushes 260W with a 8 ohm load, you'd have to add another 8 ohm cabinet to get the full 400W.

    I dunno how much that head is with 4x12s, if it's a full 100W or not, but even if it's just the 75W, 260W for the bass isn't going to be enough. I think (just my opinion) that a ratio of 100:1000 is a bit of an exaggeration. My guitarist uses a 120W amp, I was told when I did research on it (search the threads, man! Also check out the Bass Survival 101 section at that you should go AT LEAST 3x the power of the guitar amp, which in my case would have been 360, so I went with a 400W set up.

    The guitarist dude(s) all need to learn that volume isn't everything anyway...
  15. monkfill


    Jan 1, 2003
    Kansas City
    Guitars are just an odd beast. I've heard 30 watt guitar amps that are deafening. Then the guitarist has to turn up to a certain volume to "get their tone."

  16. secretdonkey


    Oct 9, 2002
    Austin, TX
    If you kept turning down the master volume because the limiter light came on, then you may have left a bunch of untapped headroom, and that could be part of the reason you couldn't get sufficient volume.

    The limiter actually allows you to not have to turn down the master volume... to basically restate what was quoted from the owner's manual, in practical terms:

    Turn the limiter all the way down and set your pre and master gains. Try some low E and F# octaves and really dig in moderately hard. You want the lights to just barely pip on, or be at the point where they are just shy of coming on. Now, if you're like me, once the drummer and guitar and everything else get cranking, you're going to actually play just a little bit harder than you did when you set your gains up, and now you're running into a bit more clipping than you want. Ease down the pregain if it is clipping, but let the limiter save you from having to let that pesky guitarist bury you - rather than turning down the master volume, simply turn up the limiter until the clipping problem is solved!!!

    Anyway - that's the way I set up the limiter on my SM-900, for fingerstyle, anyway - I'm still messing around with it, but I've experimented with cranking up the limiter on some slap stuff, with good results (the limiter on the Workingmans' series might not be as good sounding, but it could be the same circuit - I dunno) Experiment by playing with the limiter set at various levels so you can see how it affects your sound - this will help you decide for yourself how much limiter (and sacrificed dynamics) you want to live with.

    Someone correct me if I'm off on this advice - because this is my first onboard limiter, too :)