Jeff

Ooops I just noticed my amp is a gp7 not a gp12. Sorry

Hi I just joined because I to have the same amp with the same problem and I need to share what I found. Let me ask you this. Were you using a mono speaker cord? I looked at how the amp is wired and I wouldn't believe it if I hadn't seen it with my own eyes! Both the output jacks are labled "Speaker 8 Ohms" but they are not the same. The amps + and - output go to the tips and sleeves of both jacks but the High Frequency Volume control places a selectable resistance [b]from + to the[i] ring [/i]of the upper jack!!! [/b]I'm guessing that this was some wacky attempt of having the horn volume on the amp not the cab. The idea being you use a stereo speaker cable where the tip goes to the woofer and the ring going to the horn. The HFV puts resistance in series with the horn turning it up or down. BUT here's the problem... When a mono speaker cord is plugged into a stereo jack the sleeve of the plug shorts the ring to the sleeve. So when you plug a mono cord into the upper jack instead of putting the resistors on the HFV in series with a horn it is actually putting that resistance [i]IN PARALLEL WITH THE SPEAKER[/i]!!!! So with an 8Ohm speaker cab and your HFV on 7 your load is 8Ohm(speaker) in parallel with 6.6Ohm(resistor) The resistors were getting more of the power than the speaker. UNBELIEVABLE!!! unbelievable that these two jacks are both labeled "Speaker 8 Ohms" with no distinction I don't know if you did any damage to the amp but if you have a standard 8Ohm speaker that uses a standard mono plug use the bottom jack and disregaurd the HFV. If you have a cab that uses a stereo cable with the tip to the speaker and the ring to the horn use the upper jack. How the user is supposed to know that is beyond me but this amp is either poorly designed or poorly labeled. Take a look at yours, same thing? One wire from HFV to tip of upper jack one wire to ring of upper jack. Personally I'm gonna remove it. Like I said I don't know if it hurt your amp but if you got lucky and it didn't I'd remove the HFV Thanks Jeff