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Misc. newbie questions

Discussion in 'Amps and Cabs [BG]' started by rabid_granny, Jul 2, 2002.

  1. Hey, I'm starting my search for a new amp. The only amp I've owned was a little Samick SM-25B (80W - 1-10") that I bought out of ignorance.

    I have many many questions and searching has made me smarter but tired.

    Cab questions:

    1) Is the definition of "bi-ampable" the ability to add a second cab?

    2) What kind of cord do you use to connect an additional cab to a head or combo?

    3) How does the power rating for a head INCREASE when a cab is added? Is it automatic or do you have to manually increase the wattage (ie. flip a switch)?

    Pre-amp/Power-amp questions:

    4) Preamps and poweramps are only usable in a rack system? A combo or a head would already contain a pre-amp and power-amp.

    Misc. questions:

    5) What kind of output jacks are needed for DI or monitors? Is it the XLR connector?

    6) Jumping to 200W would not create a noticable difference with my current 80W amp, correct?

    7) When will Joris finish his amp FAQ and make me smart?
  2. misterk73


    Apr 11, 2002
    Flagstaff, AZ
    To get this started:

    1) I believe the definition of biampable is "able to send high frequencies and low frequencies to separate amps/cabinets."

    2) Use a speaker cable, NOT an instrument cable.

    3) My combo runs 250 watts by itself. With an extension cab, I get 350 watts -- which is actually split evenly between the two (175 watts per). 'Tis automatic with my rig.

    4) Yes, a combo or head would already have a preamp and a poweramp. With some systems, though, you can circumvent one or both.

    5) XLR connectors are good for this, but I'm not sure when/if they're absolutely necessary.

    6) Not sure what you're getting at.

    7) I want to be smart, too. Whazzup, Joris?
  3. Chasarms

    Chasarms Casual Observer Supporting Member

    May 24, 2001
    Saint Louis, MO USA

    No. Bi-amping is the process of using a crossover to split the signal at a given frequency. The higher frequencies are routed to one power amp, the lower to another. A separate cabinet is used to reproduce each.

    Typically, 10" drivers are used for the highs and a larger driver such as 15" or 18" for the lows. But variations includes horns, folded subs, etc.

    A SPEAKER cable. DO NOT use an instrument cable.

    Adding a cabinet lowers the impedance load on the amplifier. Impedance, measured in ohms, is signal resistance. Adding a cabinet lowers the resistance, therefore allowing the amp to operate more efficiently.

    Yes. A combo or head is both a preamp and power amp. However, many combos and heads have a "preamp out" feature that would allow you to use only the preamp of the unit to drive a seperate power amp. Conversely, many also have "power amp in" feature that allows you to use just the power amp section of the combo/head with a seperate power amp.

    Either of these functions usually be done using the effects loop of the combo/head.

    Either a 1/4" or XLR out can be used for a direct send. Some boards can handle both. Other require XLR. If an amp is only equipped with 1/4" send, a passive DI box is a cheap way to convert to XLR. M

    Many amps today are equipped with an XLR send. XLR should always be used to send a signal more than 20-25' as it is less noisy.

    If you are asking about noticable as in volume. The answer is "maybe." The power will help, but volume is a product of power, speaker type, efficiency, and simply the number of them that you have.

    The 80 watts isn't helping, but your lack of volume is more due to the fact that you have only one 10" speaker.

    Ask Joris.
  4. lo-end


    Jun 15, 2001
    No. Bi-ampable means you are sending high frequencies to one set of speakers and the lows to another. This is typically done with a crossover.

    Speaker cable. The difference between instrument cable and speaker cable is instrument cable is a coaxial configuration, and speaker cable is just two conductors side by side (or sometimes twisted pair, its just never coaxial.)

    The resistance changes from 8 to 4 ohms when you add a second cab (if you're using two 8 ohm cabs, that is). Amps typically put out twice as much power when you are running them with a 4 ohm load than they would with an 8 ohm one. Also note that ohms go DOWN and not up with more cabs, since ohms is a measure of resistance.

    Some amps have different output jacks that would say "4 ohm" "8 ohm" "16 ohm" and some amps just "know" what the speaker load is. I haven't seen any with a switch you have to flip. All heads are different. Read the instruction manual and you will know how to set it up.

    It depends what your head looks like. If there is a slave out or poweramp in or something like that on the back of it, you could use it with a separate preamp or poweramp. But for the most part they are for rack systems only.

    I usually see XLR connectors on DI boxes, and 1/4" or speakons on monitors.

    I think it definately would make a difference. I noticed something significant when I changed from a 100 watt trace elliot to a 160 watt marshall.

    soon enough, grasshopper. ;)
  5. Tsal


    Jan 28, 2000
    Funny, I always thought that bi-ampable cab meant that it has two sets of inputs and you can use two amps to power that cab.

    For example, a 4x10" cabinet normally amped would have amp A to drive all the speaker cones (numbered 1, 2, 3 and 4). Bi-amped would have the amp A to drive the speaker cones 1 and 2 and a second amp, the amp B would power the speaker cones 3 and 4.
  6. Chasarms

    Chasarms Casual Observer Supporting Member

    May 24, 2001
    Saint Louis, MO USA
    There are full range cabinets out there designed for bi-amping. Like a 1-15" x 2-10" and a horn type of cab. I have seen Peavey and Fender cabs like this designed for bi-amping. I am not sure if the SWR triad is set up like that or not.

    Never a 4-10 though.


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