Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

How to switch between 8,4,and 2 ohms???

Discussion in 'Amps and Cabs [BG]' started by BLonge, Jan 23, 2005.


  1. BLonge

    BLonge

    Jan 8, 2005
    Massachusetts
    just got my peavey firebass 700..looks sweet. i havent tested it year cause i still need to buy a cab. but my question is, i dont see a switch to go between the different ohm settings. how does this work? will my amp know what to do or what?
     
  2. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Since it's a solid state amp you don't need to worry about it. Only tube amps need a switch because the output transformer has specific taps to match the load to the power tubes.
     
  3. BLonge

    BLonge

    Jan 8, 2005
    Massachusetts
    does that also mean,since its solid state, i can buy a cab rated for 8 ohms, and max it out? why do the specs give you different ohm settings? im confused haha
     
  4. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    The lower the impendance, the more power the amp can put out. i.e. it is easier to drive a 4 ohm load than an 8 ohm load.

    As mentioned, with tube amps there is an output transformer that must match the cab(s) impedance. SS amps have no problem as long as you don't go below the minimum impedance.
     
  5. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Solid state amps generally have lower power ratings at higher load impedances. The values are limited by the capacity of the amplifier's power supply and the output transistors.

    The Firebass is rated 700 watts into 2 ohms, 475 watts into 4 ohms and 275 watts into 8 ohms.

    Don't let the seemingly large power output diffences fool you. If you played through the amp and compared the volume with it running through an 8 ohm cabinet and an otherwise identical (same mfr, same speakers (except for impedance)) 2 ohm cabinet, the 2 ohm cabinet would only be a teeny, weeny little bit louder...
     
  6. BLonge

    BLonge

    Jan 8, 2005
    Massachusetts
    so how can i get the maximum volume out of my amp?
     
  7. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Two 8 ohm cabs would probably be best. As BillyB_from_LZ mentioned, the difference between 8 ohm and 2 ohm is negliable. It takes twice as much power to get a noticable difference in volume.

    Two cabs will push more air than one cab and so should seem louder.

    Also, to maximize volume, use efficient speakers.
     
  8. BLonge

    BLonge

    Jan 8, 2005
    Massachusetts
    sorry for all the questions,haha,but ima newbie

    will my amp still be loud? has anyone had a firebass 700? did i blow 400 bucks while i couldve bought something better in the same prcie range?
     
  9. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Peaveys are heavy but loud amps. Just look for a good cab and rock on :bassist:
     
  10. Get two cabinets rated at 4 ohms (which will be stable at 2 ohms) and plug both into your amp. You'll be using 700 watts then. (350 going into each)
     
  11. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    A lower impedance is harder for the amp to drive because it has to put out more current for a given output voltage.
     
  12. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    Wrong. The opposite is true. It is easier on the amp to drive an 8 ohm load than a 4 ohm load.
     
  13. I have a Firebass 700 and Peavey 410 & 115 cabs, both are rated @ 4 ohms which allows me to use the max output of 7oo watts.

    IMO you did not blow $400 bucks, you could not get another amp with that power unless you buy it used. PLAY ON!!!