Amp Problem

Discussion in 'Amps and Cabs [BG]' started by Pugz, Sep 3, 2005.

  1. Ok..

    For the last few weeks, I've had a Gallien-Krueger 115SBX-II sitting in my room as I wasn't able to find the 1001rb-II available in stock anywhere at the time.


    This morning I'm delighted to see a nice parcel awaiting opening by me.

    Finally they sent the head and I imediately rig it up with my cab.

    First half an hour or so - Total Awesomeness

    After that - NO SOUND :crying:

    The power protect LED appears when I play any note and it cuts out the sound instantly at almost any volume. Only at very low volumes can you get sound without the LED coming on and without it muting but even when it does, it appears that the woofer isn't making any sound whatsoever, only the horn.

    I've tried everything from phoning the place I got it from etc but they can't do anything atm because its the weekend.

    Although they said they would replace the head piece, I have no way of telling if the problem could be because of the cabinet.

    One thing I will mention is, my brother did put the volume very high shortly after I left the room to get some food, and started playing it. I rushed back and the woofer was moving like crazy and it kind of worried me. I'm worried that he might have damaged the speaker by doing so because he went from low volume to high volume so suddenely.

    Does anyone have any suggestions as what might the problem be, or if I am right? Thanks.
  2. seansbrew

    seansbrew Supporting Member

    Oct 23, 2000
    Mesa AZ.
    Are you 100% sure alll of your connections were right? If they were not, you may have damaged the head and/or the cab. If the cab is damaged it will usually sound distorted. If the head is cutting out I would bet that it is a gonner. Make sure there are not any small buttons or settings that you might have missed during setup. Not that it will cause the amp to work right, but at least you will know next time. I speak from experience, the first time I plugged in my brand new out of the box Ampeg SVT into my spanking brand new out of the box 4x10 bxt cabs the amp worked for 10 minutes and then fried. The lights lit up on the amp and I had no sound. The problem was a small switch (bridge mono) on the back of the amp inside a small hole that I did not disengage.
  3. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Pugz...where are you located?

    Also, are you using a SPEAKER cable to connect amp to speaker?

    If you have access to a multimeter, unplug the cable from the amp and measure the resistance (ohms) across the plug. It should measure something under 8 ohms (resistance) for an 8 ohm (impedance) cabinet.

    If you don't have access to a multimeter, you could always haul the cabinet and cable down to Radio Shack and ask one of the folks there to measure it for you.

    Re-reading your original post, it almost sounds like a connection came off the woofer and the two are shorting together. I looked at and it looks like the jack plate is mounted from the outside of the cabinet.

    In the interest of protecting your 15 from screw driver punctures (a very fast way to ruin one's day...), I'd recommend removing the six screws from the jack plate and looking inside the cabinet at the back of the 15. A flashlight will be your best friend here!!!

    Look at the wiring terminals on the 15 to make sure that there are two wires connected (one on each side).

    If I'm talking down to you, I apologize and mean no offense.

    The 15 is probably made my Eminence which usually means that the connections will be made using Quick Connect terminals (sometimes called Fastons). My guess is that one of the wires from the crossover (and jack plate) came off of the speaker's wiring terminal during your brother's little "session" and shorted out to the other one. This would cause your amp to shutdown when you turn the volume up but might allow some signal through to the tweeter if the volume is really low.

    Please keep us posted on how this is all sorting out!

    Good luck!!!!
  4. I'm located in the UK but as for compatible power ratings its ok.

    I'm using the standard GK Speakon cable that came with the cabinet. I'm sending back the head as there were several things wrong with yet im still worried about the cabinet.

    I don't want to open it up because its stated that it will can void warranty.
  5. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    OK, fair enough..

    If you were using the GK cable, that means that you were biamping the cabinet, correct?

    I still think that a connection to the woofer might be loose inside the cabinet. Especially if it had to travel all the way from California to the UK.

    I'd recommend that you find a way to measure the resistance of the cabinet going in through the 1/4 in. jack...

    Does your amp have a mains voltage switch on the back and is it set for 220 Vac (as opposed to 120 Vac)?

    I had another idea. Since the amp is solid state, you won't hurt it by running it without a load. What happens if you (with the the speaker cable unplugged from the amp) turn on the amp, plug in your bass and turn up the volume and start playing? If the amp is faulty, I suspect that you'd get the same result as with a load attached. If the problem is beyond the amp (as I suspect) then it won't shut off.

    Please consider giving this a try (you're already going to send the amp back...right) ...and please let me know what happens.

    Good luck!!!
  6. tadawson


    Aug 24, 2005
    Lewisville, TX
    There are also a couple of protection fuses/lamps on the crossover in the SBX cabs. Pull out the crossover and have a look - if one failed, no sound out of either high or low would be the result. The 1001RB-II has more power than a single SBX is rated for, so you may well have popped the protection. That does not, however, explain the protect light on the head . . . . it may also be a defective head. Since the high and low on both the head and SBX cab are separated, the problem, based on your description, could be in either . . . .

    - Tim

  7. Ok. I numbered your posts points to make this response easier to understand.

    1. Yes, I was bi-amping it. I definately had all the settings right for that.

    2. As Gallien-Krueger is an American make it has to be shipped from there to Europe. To make matters worse, I ordered mine from Germany. So its done 3 trips.

    3. How can I go about doing this?

    4. I does not have a switch no, but it has a label on it saying "240v / 50hz" which I think is ok.

    5. I tried this idea and as you suspected, I think it may be beeyond the amp. I played through it at a volume loud enough for it to cut out easily when played normally, and with no cabinet attached to it, the blue light stayed on and it was fine. This suggests to me, that only when there is sound being processed by the cabinet does it cut out therefore it seems likely it may be the cab :(

    Even though it seems that the Head is ok, it still had some errors with it (Power button gets jammed and has to be pulled out to turn it off with pliers / It came with no instruction manual or a speakon cable (fortunately I had one provided with my cab) so I'm sending that back to get a replacement by thursday.

    Thanks for the help so far though everyone, I seem to be getting closer to knowing what the problem is now.
  8. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Good luck with getting the replacement amp...seems like the seller sold you a used amp as new.

    BTW, you can get a manual for it at

    Please keep us posted on what happens with the cabinet...