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Unlocking the Full Potential of my Amp

Discussion in 'Amps and Cabs [BG]' started by Bassline_Delux, May 16, 2005.


  1. I read this thread:

    http://www.talkbass.com/forum/showthread.php?t=178367&highlight=dummy+load

    But didn't quite get what I was lookign for.


    Okay, I have a Peavey Firebass 700 (Great Amp BTW, I tried a 700RB and a 1001RB..I prefer mine :) )

    Anyway, I have two 8ohm cabs. The outputs are in parallel so plugging in both my cabs makes a load of 4Ohms. My Firebass puts out 475W@4Ohms. BUT it puts out 700W@2Ohms. Is there anyway I could perhaps add some sorta dummy load so that my amp would be putting out its full 700W? For headroom purposes only. Oh yeah, I'm also curious as to how this would affect the tone, if at all.
     
  2. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    no. well you could, but then only 1/2 of the wattage would be going to your speakers, thus reducing your headroom. :meh:
     
  3. it could be done, i think, if you had both your cabs connected out of one of the amp outputs (daisy chained)

    But i dunno otherwise, its not that much of a volume difference anyway
     
  4. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    those 2 eight ohm cabs will always give you a 4 ohm load. using it liek you have it now gives them 475 watts combining them with a 4 ohm dummy load gives them 300 watts. not a step forward.
     
  5. Happy MurphDay

    Happy MurphDay

    Mar 9, 2004
    around
    i don't know how you are looking as far as budget wise, size or anything else, but you could add another 2x10 that is an 8 ohm cab reducing the total ohmage to 2.67, plus two more tens, again, I don't know your situation
     
  6. umm, daisy chaining wouldnt get anything accomplished, depending on whether the cab is wired in series or parallel, you would either be running it at 16 ohms or 4 ohms respectively. you could check what impedence the individual speakers are in your cabs and then figure out a way to make them 4 ohms, im not really sure if its possible im too tired to think now, but here is a handy speaker impedence calculator - http://colomar.com/Shavano/impedance_proc.php . that will do the math for you.
     
  7. If you have $1000 to spend, and find a $500 amp you like, you could light the other $500 on fire to get the "full potential" out of your money.

    Wait a minute.... let me reconsider. The point of having $1000 is ending up with $1000 worth of stuff to show for it.

    The point of getting extra wattage out of your amp is putting it into speakers and getting sound out of it.

    The dummy load converts ALL the extra wattage coming out of the amp INTO HEAT, not sound, not unlike setting the extra $500 in your bank account on fire. Its actually a worse than that, you lose part of the original $500 in the dummy load investment scheme. Here's why.

    Getting another 4 ohm speaker to lower the ohms to the amp's rated minimum ohms WILL maximize the amps potential, and give you 700W into speakers producing sound. Good thing.

    Now you have 475w@4 ohms total going to your speakers. Add a dummy load (4 ohms) to get 700W out of your amp. Now you have 350w going to your speakers, and 350W going up in smoke in the dummy load. You have just LOST 125W that used to be available to go to your speaker. That's the dummy load investment manager's fees. You're moving backwards, not forwards.

    Randy
     
  8. Only a transformer could make the 4 ohms speaker load look like 2 ohms at the amp and actually feed that extra power to the speakers. They used them in tube amps years ago probably because they had to to match cab impedances to prevent tube damage. Basically I think the tube output stages were naturally much higher impedance (=high voltage, low current) than 8 or 4 ohms, they couldn't drive speakers directly. As long as you have to have a transformer, no problem adding different taps to get max power out of a range of speaker loads. Making the most of a bad situation.

    Solid state amps are more forgiving of a wider range of ouptut loads, their normal output impedence is comparable to speakers, so they will drive speakers directly, within reason.

    But there's no reason at all they couldn't use transformers for solid state amps and get the full power out of all the common speaker impedences, just like the old tube amps. So why don't they use them?

    Cost, weight, heat, freq response problems. Their disadvantages outweight their ability to get max power out of many loads. When they were essential, you had to make the best of it.

    Your bitchy mother-in-law that lives with you makes great spaghetti. Yeah, you eat the spaghetti. But if you get the chance to kick her ass out, DO IT!!! You can make your own spaghetti if you have to. Transformers were a necessary evil for tube amps.

    Randy
     
  9. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    getting warmer
    OMG that is the funniest thing I've read here in a while.

    To the original poster, do you feel that the amp is not up to the task of whatever it you are doing? If you want 700W just so you can say "I've got 700W" or if the rig isn't loud enough then yeah, get another 4 ohm cab or better yet 2 more 8ohm cabs. If it is loud enough as is, I'd say save the money for some of Randy's mother in law's spaghetti.