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running a cab through PA.......safe?

Discussion in 'Amps and Cabs [BG]' started by jrthebassguy, Jun 2, 2001.

  1. Ok, well I might be getting a job soon, so i can finally get a new amp setup!

    Well, right now my idea is buy a 4x10 cab (unsure which brand though) and run it through the PA until i can afford a head for it.

    But i told my guitarist the idea, and he said it would blow the cab. He said PAs run on instrument cables, not speaker cables. And since cabs run on speaker cables, not instrument cables, he said i would blow the cab.

    Is this true?
  2. Angus

    Angus Supporting Member

    Apr 16, 2000
    Palo Alto, CA

    Through the PA? That usually means you are miking the cab and sending the microphone line to the board (then out the PA).

    Where is the power coming from? Do you mean using the PA's power amps? I doubt you'd be able to do that.

    However, powering using instrument cables vs. speaker cables won't blow the speaker/cab, it'll just fry the cable. Besides, PA's use speaker cables, I believe.

    Would you please rephrase what you're trying to get at? :D
  3. I think that it is pretty easy... instruments go in on instrument cables, speaker lines go out on speaker cables, therefore PA's use both.... As long as your cab has the power handling and correct impedance you will be fine, it is not as though you are using a different kind of signal. Some people I know suggest using a bass preamp through a PA power amp to use as instrument amplification..

    The only thing is that PA's usually use full range cabs, while bass cabs are meant for the low frequency response...

    If i have conflicted the truth, please notify me!!!

    Thanks buds

  4. yeah, i mean the PA's power amps powering the cab.
  5. Angus

    Angus Supporting Member

    Apr 16, 2000
    Palo Alto, CA
    Ok, yeah, most clubs won't let you do that, unless you've got a DI to go direct into the PA, and have a line from the PA go to your amp...but you won't really need that, since you're already going through the PA as it is. If there's a PA, you'll probably have monitors, so you should be able to hear yourself. Make sense?

    If I were you, I'd buy a 4x10 and use your Hartke 15 to power it. Put them side by side, since you don't want to set the 4x10 on the combo, and you don't want to put a 1x15 on a 4x10. That is...until you get enough money for a head, if you even need one! Sound good?
  6. Well, its our own PA so a club wouldnt care or not if we did it.

    And i emailed Hartke not too long ago about adding on a cab and they said if I did so It would fry the amp inside because it wouldnt be able to handle it. Unless the guy was a total idiot. He was after all a Samson employee, not a Hartke employee (Samson owns Hartke). He said that the "Line Out" jack was meant for going into a PA to go to monitors, not cabs.
  7. White_Knight


    Mar 19, 2000
    Your line out jack sends a line level signal out: either to a PA, another amplifier, a recording console, etc. Even if you connected it to a speaker cab, you wouldn't hear anything (or at least almost nothing) because a line out has much less voltage than a speaker needs to operate.

    What I would do in your case is use the Hartke as a stage monitor, then run the line out to your PA system. From there, run from the speaker terminals of your PA power amp to you new bass cab.
  8. Angus

    Angus Supporting Member

    Apr 16, 2000
    Palo Alto, CA
    How powerful is the PA?
  9. If the PA is just for vocals you don't want to mike other instruments especially bass! Bass takes a lot more watts to reproduce so it takes away from the vocals and can really do weird things to the overall sound too. I would not risk hurting the vocals.
  10. Brad Johnson

    Brad Johnson SUSPENDED Supporting Member

    Mar 8, 2000
    Gaithersburg, Md
    DR Strings
    The advice here is interesting. Is it assumed that the PA is capable of sending "bass only" to his cab?

    Jake, do you want only yourself in this cab or everything that's going into the PA?
  11. Well, thats what I wanted to do from the start, I guess I just worded my question wrong.

    I'm not sure, to tell you the truth.
  12. White_Knight


    Mar 19, 2000
    Brad brings up a good point: unless you're the only one running through the PA, your cabinent is going to get the entire mix (vocals, drums, guitar, etc.) which really won't do you much good at all. The advice I posted above is for if you just had the cabinent and a PA power amp for your personal use.
  13. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Well, if you do what White Knight says, your cabinet will be just another PA speaker ... everything, including your bass, will be going through it. How do you plan to separate out your signal? You could try this.

    Send a mono PA mix to one side of the stereo PA amp, and run both PA speakers off that side. Then route your DI'd bass signal to one channel of the PA, but don't put that channel in the PA mix. Rather, use a channel direct out to the other half of the PA amp, and send the output of the amp to your bass cab. Simple enough.
  14. well, id be running my own independant channel, so only my bass would be going through it. right?
  15. Brad Johnson

    Brad Johnson SUSPENDED Supporting Member

    Mar 8, 2000
    Gaithersburg, Md
    DR Strings
    Depends on what you mean by an independent channel, Jake;). Munji's example of running one side of a stereo PA would give you an independent stereo channel.

    OTOH If you mean that you'll be plugging into a channel on the board you'll probably need to be able to do a sub or solo mix down to a monitor...it's done all the time on bigger PA systems.

    Is this the best way to do it?...beats me. I know some people who play direct with no onstage amp and rely solely on monitors. This requires (IMO) nice monitors which aren't cheap.
  16. FleaisGod

    FleaisGod Guest

    Jun 18, 2000
    Atlanta, GA
    If your planning on using the PA for your bass, whats the point of getting a bass cab? why not a bass monitor?

  17. mmmm, I've done gigs where vocals and instruments (including bass) has gone through the house system, and the sound has been excellent. I suppose it depends on (a) the quality of the sound system, and (b) having a sound-engineer who knows what he's doing. I know it's a damned sight easier to balance and set up when everything goes through the board.

    - Wil
  18. Ty McNeely

    Ty McNeely

    Mar 27, 2000
    I wondered the same thing, but most PA power amps run at 2 ohms, and most cabs can't handle that kinda of power. So unless you got 2 Megoliaths or something, the PA power amp would be pushing too much.
  19. Brad Johnson

    Brad Johnson SUSPENDED Supporting Member

    Mar 8, 2000
    Gaithersburg, Md
    DR Strings
    If you're sending a monitor mix to the cab or one side of a two channel power amp, as long as you adjust the gain properly there shouldn't be a problem.
  20. mikezimmerman

    mikezimmerman Supporting Member

    Apr 29, 2001
    Omaha, Nebraska
    "ohms" is not power--ohms is impedence, which is a characteristic of the speaker cabinet. The cab will have 4 ohms, 8 ohms, etc. of impedence. If the power amp is rated to run at 2 ohms, that means it's safe to connect cabinets that have a combined impedence of 2 ohms or greater (like a pair of 4 ohm cabinets). The minimum impedence rating has nothing to with how much power it puts out, except in the sense that most solid state amps put out more power when they're attached to speakers with lower impedence.

    "watts" is power, and it is a characteristic of the power amp. If a cabinet is rated for 350 watts, that usually means it can handle 350 watts or so of power coming from the amplifier (give or take some).

    For what it's worth, the Megalith has an impedence of 4 ohms, and is rated for 1200 watts of power.


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