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bi-amp brigdge mode

Discussion in 'Amps [BG]' started by morewattsplease, Nov 19, 2012.


  1. morewattsplease

    morewattsplease

    Joined:
    Apr 29, 2012
    Location:
    libertyville, chicago
    long intro, sorry, it may be a "too long did not read"

    So the rig I use now is a Warwick Quad VI through either a warwick 411 pro (4x10 with horn) or an emperor cabinets 4x12.

    (I enjoy both cabs, and I realize there is a distaste for emperor cabinets, but I really love mine so let us please not have this be a flame war, I've been guilty of flame in the past so I'm not claiming sainthood, I just dont need to be told that the cab with a sound I desire will not give me the desired sound. That being said there is a reason I keep both when I should really only need one generally)

    Enough of that. My Quad VI has been making some scary noises lately, intense staticy feedbacky sounds...IDK enough about amps to discern what is wrong. Not really sure if it may just be some cables' issues, or the amp deteriorating. Its gotta be at least 11 years old, bought it used, and have since taken good care of it, but maybe it needs its "oil changed" (it is a tube/mosfet)

    ****So first of all: Any good amp techs in the lake county illinois? (chicago northshore) I like the music store down the street, they have a great record in my book, but IDK, I'd like to find a brick and mortar place that may specialize in amp tech.*****

    Secondly, with this scare in mind, I've renewed my desire for something new, something that means less to me than the Quad VI (first "real" amp, long story, and I love it). I don't have a huge budget, and come buying time I'll be looking a lot at used gear and at reviews of whatever I buy, but for the moment the Carvin BX500 looks great. good for the money and all that.
    BUT, I worry, that down the road I may want the extra power of something bigger. Therefore I am curious about the BX1500, because it would allow me to gain some volume if need be.
    http://www.carvinguitars.com/products/BX1500

    **********My questions:************
    -the amp tech question as stated above
    -how does figuring out the minimum load of bridged amplifiers work? is it just whichever cab is plugged into whichever output? or is there math involved?
    -How does the bridging/crossover work on the BX1500? do those knobs allow me to send the Highs to the 4x10 and lows to the 4x12 so that I can avoid phasing issues of mixed speaker sizes? or is the function of bridging not that? from what I can see once in bridged mode you may hit the crossover switch and then set the amps "1" and "2" to send a selectable blend of highs and lows......
    **************the end****************

    (sorry for long post, seen so many ask a ? and be asked for more info, just wanted to be thorough, plus I'm a philosophy major, not typically short winded)
     
  2. morewattsplease

    morewattsplease

    Joined:
    Apr 29, 2012
    Location:
    libertyville, chicago
    Note: when buying I'd love to find a score on a cheap thunderfunk, SWR, Genz Benz, or something, but the fact that a new, warranty insured, always available carvin out there that seems on paper to fit what I want is pretty appetizing.
     
  3. morewattsplease

    morewattsplease

    Joined:
    Apr 29, 2012
    Location:
    libertyville, chicago
    as I read more I guess Bi amping and bridging are different so I definitely misused some terminology, but my questions still apply, I think, as follows
    **********My questions:************
    -the amp tech question as stated above
    -how does figuring out the minimum load of #BI AMPED# amplifiers work? is it just whichever cab is plugged into whichever output? or is there math involved?
    -How does the #BI AMPING#/crossover work on the BX1500? do those knobs allow me to send the Highs to the 4x10 and lows to the 4x12 so that I can avoid phasing issues of mixed speaker sizes? or is the function of #BI AMPING# not that? from what I can see once in #BI AMPED# mode you may hit the crossover switch and then set the amps "1" and "2" to send a selectable blend of highs and lows......
    **************the end****************
    sorry
     
  4. Downunderwonder

    Downunderwonder

    Joined:
    Aug 26, 2009
    Location:
    New Zealand
    Ordinarily that kind of true biamp is useful to split highs and lows for HiFi bass. A sub type cab and a 2x10 would be very loud and very very clear. This is the kind of rig that is good for carrying a small to middling room from the stage but a royal pain for the soundguy if you aren't.
     
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  6. Downunderwonder

    Downunderwonder

    Joined:
    Aug 26, 2009
    Location:
    New Zealand
    Each channel has a minimum load. Usually the minimum load for the bridge mode is double the individual channel minimum so you don't gain anything. If you happen to have a very strong higher impedance cab and relatively weak amp then bridging can work.
     
  7. T-Bird

    T-Bird

    Joined:
    Apr 29, 2007
    Location:
    Finland (Northern Europe)
    Hi.

    ^Basically this.

    Except that You do "gain" a larger voltage swing onto the terminals than You would with an individual channel (=amp), should you need that for some reason.

    User assignable bridging looks good on paper, but it rarely offers any advantage over individual channels.
    Sells a lot of gear though ;).

    As You already discovered by yourself, bridging and Bi-Amping are totally different things. I don't know about the BX1500 Bi-Amp features, but usually you just adjust the common cross-over point for both the LPF and HPF, and that's it. You can't usually adjust the phase of the either band, nor can you select (or even know) the slope type used. Both of the latter would be required for optimal performance when mix-matching cabs of unknown characteristics and phase behaviour.

    A dedicated 2 way cross-over, even a cheap one, usually does the job better.

    The only area where those inbuilt cross-overs would offer advantage today IMHO, would be of using a bass cab for lows, and a guitar cab for highs. So it would protect the guitar cab, nothing more, nothing less.

    Regards
    Sam
     
  8. BassmanPaul

    BassmanPaul Gold Supporting Member

    Joined:
    Aug 25, 2007
    Location:
    Toronto Ontario Canada
    You can bridge the BX1500 into a minimum of 4Ω. You can only use the "Bridge" output socket when switched to bridge. Never use a 1/4" phone speaker cable in bridge. It's unsafe for both you and the amp. Speakons only. I have been using stereo power amps for decades and have yet to feel the need to bridge any of them.

    When bi-amping one power amp feeds the high range sockets and the other feeds the low range sockets. They are clearly marked. It's pointless bi-amping into two full range cabinets. It's also a waste of resources as half the amps available power will be driving the highs where a 100W is well more than enough.
     
  9. dincz

    dincz

    Joined:
    Sep 25, 2010
    Location:
    Czech Republic
    On the other hand, bridging is useful if you're driving a single 8 ohm cab and one half of the amp doesn't provide enough power. I've also used a variety of power amps over the past 20 years and they've all been run bridged into a variety of single 8 ohm cabs.
     
  10. will33

    will33

    Joined:
    May 22, 2006
    Location:
    austin,tx
    Disclosures:
    Use of this field for any other purpose is prohibited
    A. Put new battery in bass if it's an active bass.

    B. Wiggle cord in jack on bass. It may have a broken solder joint or bad ground.

    C. Make sure all cables used are good.

    D. Wiggle the cable in the input jack on the amp. It's possible it may have a broken solder joint or cracked circuit board.

    E. Run a guitar cord from the effects send jack to the effects return jack. These are switching jacks and can sometimes stick.

    F. Use a second amp for this. Run a guitar cord from the preamp out or effects send jack on problem amp to the poweramp in or effects return on good amp. See if you get a clean signal.

    G. Use second amp again. This time run guitar cord from the preamp out or effects send jack on the good amp to the poweramp in or effects return on the problem amp. See if you get a clean signal.

    H. Need to take cover off for this. Check that the preamp tube is seated in the socket and that the socket is in good condition. Tap on tube with a pencil and see if it makes noise. Or just try another tube, they're only $10-$15.

    I. Look at the input jack for bad connections or cracks in the circuit board. Look around for any other obviously loose or burned looking parts or bad wire connections or cracks in circuit boards. If it has any plug-in wire connectors, the kind you don't solder, check that those are seated good.




    If none of that helps anything, take it to the tech.
     
  11. BassmanPaul

    BassmanPaul Gold Supporting Member

    Joined:
    Aug 25, 2007
    Location:
    Toronto Ontario Canada
    Agreed. Bridging is best when trying to get more voltage swing across a higher impedance load. Less useful when trying to squeeze every last drop of power into a lower impedance. In my case I bought 4Ω cabinets as all my amps are capable of running into 2Ω loads per channel. I use a pair at a gig, one on each channel. Used unwisely bridging can easily lead to blown drivers.
     
  12. morewattsplease

    morewattsplease

    Joined:
    Apr 29, 2012
    Location:
    libertyville, chicago
    Thanks paul, as well as to everyone else. I may still consider this amp because the bridging would be a nice option to have, but that is a little too much power for my emperor cab. Actually a lot too much because its rater at 1400 watts, and I think it realistically is more like 1000, and I heard somewhere to give yourself a nice cushion on ratings....
    Bi amping is bad into two full range bass cabs, man I knew this solution I rigged up in my head was too good to be true
     
  13. will33

    will33

    Joined:
    May 22, 2006
    Location:
    austin,tx
    Disclosures:
    Use of this field for any other purpose is prohibited
    The 2-channel amp still has an advantage with your cabs. That being you can run one off each channel and control their power/volume independently. When you run them both off a mono amp, your limited to what the weaker cab can handle, though I'd think a 412 by itself, assuming it's a bass cab, would be loud enough for anything.
     
  14. Downunderwonder

    Downunderwonder

    Joined:
    Aug 26, 2009
    Location:
    New Zealand
    Biamping isn't bad, it's good. It won't be anywhere near as loud as the full range cabs driven full range but loud isn't everything.

    What is bad is carting a 4x12 or 4x10 to do the work of a 6" driver or two.

    Will gave you a good rundown. Be careful with poking around inside. Checking a preamp tube is seated and poking around the input jack is ok but there is stuff in the power amp which can bite long after it's been turned off.
     
  15. morewattsplease

    morewattsplease

    Joined:
    Apr 29, 2012
    Location:
    libertyville, chicago
    thanks guys, and as far as the amp repair if I can't figure it out easily I'll just continue my search for an amp tech in my area.
     
  16. BassmanPaul

    BassmanPaul Gold Supporting Member

    Joined:
    Aug 25, 2007
    Location:
    Toronto Ontario Canada
    Just for information, if a power amp has a minimum load figure of 4Ω per channel then it will bridge into 8Ω. If the amp can handle 2Ω per channel then 4Ω is the minimum bridge load. That said, not all amps can be bridged or even have a provision for it.
     

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