purpose of a power amp

Discussion in 'Amps and Cabs [BG]' started by Fred19137, Feb 14, 2009.

  1. Fred19137


    Jan 23, 2009
    active musician
    I apologize, I tried to find a thread that answered this question, but it gets frustrating to try to read through all of those threads for your answer that you would think would be obvious.
    I have a 150W head. I want to increase its power, but want to keep the head. Is a power amp what I want and how would I go about using it. Do I take the speaker outs from my 150 and plug those into the power amp or do I use the direct out? I was just wondering
    Thank you for your time.:meh:
  2. hmm no a power amp is generally not used like this.

    bass>>>Preamp>>>>Power Amp>>>Cabinet(s)

    Your head is both a preamp and a power amp

    If you could conjure up some way of bypassing the power amp on your head, and running this signal through a power amp, it would work.

    However, i will suggest NOT plugging the speaker outs from your head into a power amp. You will damage something

    Probably easiest to sell your head and buy a more powerful one.
  3. You can plug the existing head into the power amp via the head effects send, which is usually post-pre and pre-power.

    You'd have to really like the 150W head, and want an awful lot more power I think to make it worth it. Might just be better buying a bigger head; your head and a power amp might be quite a lot to lug around. Might be better to just buy another cab, too. More to lug around still, of course.
  4. Fred19137


    Jan 23, 2009
    active musician
    thank you so much!!!!!!!!!! I can use my line out plug which uses the preamp but not the power amp. I could then send that signal to a more powerful power amp. Thanx ur the best!!!!!!!
  5. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Eh, I looked up your gear in your profile, and I don't recommend it. You're using a combo, so it's very possible that if you add power to it, you'll blow the speaker in short order. Part of keeping costs down on combos is using speakers that are rated for the amp and not much more.
  6. What Jimmy said.
  7. JazzbassArt


    Dec 12, 2004
    Andover, MN
    True, you will put the driver at risk, but there's nothing wrong with starting your rack of the future, with a higher quality, lightweight, powerful amp. QSC or something similar. It's a great way of extracting the max from a cabinet. Just be aware when too much gain is too much. I guarantee, when the voice coil fuses, you'll have graduated from the school of hard knocks of impending speaker failure warning sounds.
  8. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    +1. You'd need an additional speaker to handle the output of the power amp, and chances are the result would be no better than just adding an extension cab to your existing rig. BTW, when power is the limitation the rule of thumb is you need to quadruple it to make it worthwhile.
  9. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    Hey Fred, listen to Jimmy and Bill. You're trying to re-invent the wheel here. My advice is, keep the stuff you have, and start putting together a bigger bass rig, one piece at a time. I personally prefer all-in-one heads, but you can go whatever route you want, head, pre/pwr, multiple small cabs, one giant cab,..etc. There's alot of really good bass gear on the market, and generally it's expensive, unless you buy used gear. Let the first buyer take the hit. Good luck, and don't do the power amp hooked up from a small combo amp, really.
  10. bongomania

    bongomania Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
  11. rptrsn2


    Feb 21, 2008
    Northeast Missouri
    Endorsing Artist: Aurora Strings
    if you are going to eventually go to preamp-power-then cabs it will be fine. when all i had was a combo i new iwas going to buy a bigger head and cabs so i bought my cabs first and borrowed a power amp and it worked fine. don,t now that i would have bought one though if wasn,t going to keep using it.
  12. Well, yes, when he said head I assumed he meant, well, head, and not a combo. Obviously madness to plug the line out into a power amp and then back into the combo speaker.

    Buying an extra cab might increase the noise a bit. And be the first step to a full rig.
  13. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    I have a feeling he got his answer from the first 2 replies, and he's going to do it regardless of what anyone else says. Silence speaks volumes ;)
  14. Fred19137


    Jan 23, 2009
    active musician
    It makes sense. I'll wait till I can just get the proper stuff.
    I'm just the kinda guy who takes his stuff and trys to figure out all of the parts of it how it works. I'll wait till I learn completely before I go "f" ing things up. I learned the hard way a while ago
  15. davecanady

    davecanady Guest

    Aug 24, 2008
    It doesn't say what Crate combo you have. Find out if it can use a second cab. If it presently is pushing an 8 ohm 15" speaker, you might be able to add a second 8 Ohm cab.... Read your amp's manual. It will tell you. If this is the case, your 150 watt at 8 ohms amp jumps to 250 watts +or- at 4 ohms and you'll have more speaker surface pushing sound.

    Crate's BT220 has an extention cab jack. Does yours?

    If you can do this, buy a good higher wattage cab (210, 410, 212) which will eventually become part of your new rig when you buy a new head.
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