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Confused about wattage & resistance

Discussion in 'Amps, Mics & Pickups [DB]' started by hdiddy, Jun 18, 2004.


  1. hdiddy

    hdiddy Official Forum Flunkee Supporting Member

    Mar 16, 2004
    San Francisco, CA
    Hi fellas,

    I'm beginning my quest on the right DB rig for myself in the future. After reading many different threads about the AI and EA amps & cabs, I think I've settled between the iAmp500 (or maybe a Clarus 2 for the 2nd channel). The iAmp500 sounds really good though. Mainly cuz it has a lot of power and I need the feature of being able to use headphones along with an external input (like a cd) to practice (from what Bob G's site says). My intention is to put the $$$ out in the beginning instead of upgrading later on. The iAmp500 should give me the flexibility I want with different cabs along with great sound.

    EDIT: I currently am running an underwood pickup, but will consider switching to a mic later on, or even switch back and forth depending on the application.

    What I'm confused about is the wattage and resistance equations to pair up the head with a cab. Wattage is how much power is going to the amp, no? So if for a given amount of resistance (say 4 ohms), will the 500 watts be too much and blow out a 250 watt cab? Or rather, will I damage the cab by underpowering it (like a 100 watt head into a 250 watt cab)?

    I saw another thread discussing this sort of thing, but there were alot of variables being thrown around and it got confusing. Ideally, I'd like to pair the 500 with a wizzy cab or a 1x10 cab for regular small stuff and still have the option to go with a bigger speaker later on.

    Thanks for clearing up my ignorance.
     
  2. McBass

    McBass

    Mar 31, 2004
    Brooklyn, NY
    Whatever amp you buy will have its output power rating specified. The wattage rating you're talking about is probably the amp's output power, or the power it's going to put into a speaker. An original clarus will put out 300 watts at 2 ohms. A GK 112mb combo will put out 150 watts at 4 ohms. So , ideally, if you're going to get an amp rated at 500 watts into 4ohms, you'll want a speaker that is rated to handle 500 watts with 4 or more ohms of resistance. The higher the resistance of the speaker, the less power the amp can push into it. The same clarus is rated around 200 or 220 watts into 8ohms. You won't risk blowing out a speaker rated at 500 watts with an amp rated at 100 watts.

    P.S.
    You'll find that there is no way to avoid upgrading sooner rather than later. Your best bet is to get highly regarded, reliable, good sounding equipment. The higher resale value of these items can insulate you against upgrading costs. The best example being walter woods amps. They are always in demand, new or used, and sometimes go for more used than new depending on demand for a particular model. Not to mention good carved basses that almost always appreciate with time.
     
  3. hdiddy

    hdiddy Official Forum Flunkee Supporting Member

    Mar 16, 2004
    San Francisco, CA
    Which then means that if I get an iAmp500 (500 watts @ 4 ohms) and hook it up to a Wizzy 112 (350 watts @ 4ohms), then there's a good chance I'll blow the cab out.

    Too bad... I was looking for a small rig since I already have an EB setup and dont' really need to double with a DB rig. A bigger set of speakers would be too heavy to haul to a small gig/rehearsal to be used with an iAmp most likely.

    So then for me, it'd be a toss up between an AI Coda vs. a Clarus 2 + Wizzy 112. Decisions, decisions, decisions...

    Thanks McCod.
     
  4. Sam Sherry

    Sam Sherry Inadvertent Microtonalist Supporting Member

    Sep 26, 2001
    Portland, ME
    Euphonic Audio "Player"
    This topic is covered in excruciating detail in this thread.

    You're very rarely going to be putting full power out of your amp playing regularly. Yeah, if you play thumbstyle EB (or if your jazz act includes hitting the pickup with the drummer's forehead) and you're producing standing waves, you'd be wise to invest in the sturdier, heavier, more expensive driver. But practically, it's unlikely that you'll blow the driver just playing DB as you've described.

    See if you can take a test-drive.
     
  5. hdiddy

    hdiddy Official Forum Flunkee Supporting Member

    Mar 16, 2004
    San Francisco, CA
    Yes, that was the thread that was a little bit confusing but reading the end of the thread helped.

    So Sam - if I go ahead and put 500 watts @ 4 ohms into a 350 watt cab (also @ 4ohms), it's still ok, AS LONG as I don't turn the volume up to 11 (or 4-5 at most for that matter). Is that what you mean? I just want to be absolutely clear on it at the cost of potentially looking stupid. :bag:

    I've heard some guys (maybe yourself as well) running Walter Woods heads with high wattage into smaller cabs simply because you have more headroom and that the signal is cleaner.

    Off-topic: Hey... so how did you gig with Mimi Fox go? Are we going to hear a recording?
     
  6. hdiddy

    hdiddy Official Forum Flunkee Supporting Member

    Mar 16, 2004
    San Francisco, CA
    I think I found my answer after reading this (I must've screwed up the search somehow):
    http://www.talkbass.com/forum/showthread.php?t=122165&highlight=iAmp+800

    And my head must've been off in LALA land regarding Sam's message. :confused: :D So yeah... I don't plan on turning it up to a point to damage the cab.

    Thanks y'all. Looks like I'll go with the 500 and will try it out in Santa Cruz before buying. Yeehaw! :hyper:
     
  7. Nuno A.

    Nuno A. Velvet Strings Customer Service

    Jul 9, 2001
    SWITZERLAND
    I use an iamp 500 + a EA wizzy, amazing tone , loud and light, you cant go wrong...about blowing the wizzy? i talked with Gary from EA and he told me i shouldnt worry about it, you're not going to use the iamp at full power always hum?
    try it, i love this rig, best rig i ever had, TRY IT.....

    NUNO
     
  8. Sam Sherry

    Sam Sherry Inadvertent Microtonalist Supporting Member

    Sep 26, 2001
    Portland, ME
    Euphonic Audio "Player"
    Not quite. What I mean is that a switching amp delivers only as much power as it "needs" to. So if you're plugging along playing mid-volume mid-register stuff with the amp set on "11" you're still only going to be delivering xxx watts to the speaker. And then you drop down for a nice triple-forte low-E and voila, you're delivering yyy watts.


    Right, you got it. FWIW, I'm the other way but not by design. My 1982 WW-1 is rated at a nominal 100 watts into 8 ohms, which would be about 175 watts into 4 ohms. I've often heard these amps spec out higher on an oscilloscope but I don't care: It pushes what it pushes, and I dig the tone. It's loud enough for me -- if I need louder than that, there's generally a PA.


    The gig was enormous fun and Mimi was great. She was on the last show of her 10-day East Coast swing and she left it all on the stage. She swung much harder than the new record, and the new record's no slouch, too!

    I decided not to post the tape for two reasons. First, I really want feedback on my "alone" playing -- I need the help, man. Second, I taped Mimi's show using my office dictation recorder and it sounded, um, "functional" if perfecty musical. You're nice to ask, man, and you're lucky to have had the chance to work with Mimi.
     
  9. hdiddy

    hdiddy Official Forum Flunkee Supporting Member

    Mar 16, 2004
    San Francisco, CA
    Right... the speaker is only going to get pushed with the signal amount that's coming from the head. I guess we were talking about MAX output from the head, and I doubt if I'll ever get to 50-70% of full power. And the cab simply isn't going to blow up if I turn it all the way up and it's broadcasting nothing. Silence just doesn't do that. :)

    Glad to hear it. Too bad about the recording. I'll have to listen to your solo piece some more... heard it earlier today.

    Yeah, Mimi rocks. She's always playing like she's on fire. Great teacher too, she even lets her students (though I didn't do it) sit in with her at her regular weekly gig. Wonder if she'll let me sit in on bass once I get my chops up. That would be too good to be true.

    I'll update you guys once I get the EA stuff. :D