Members tonynorie Posted November 3, 2006 Members Share Posted November 3, 2006 I'm posting this in Live Sound because it involves a question mostly about a power amp: I usually run my SVT3 275w Ampeg head through a 4x10 Hartke 8 ohm 400w cab but need more power for an outside gig tomorrow. I took a QSC2450 500w per channel amp out of the p.a. rack, hooked up one side, and it only seemed to put out about half or less than the Ampeg! I then switched the dip switches to the bridge position, but no difference. What the heck am I doing wrong? Thanks guys! Link to comment Share on other sites More sharing options...
Members tonynorie Posted November 3, 2006 Author Members Share Posted November 3, 2006 I neglected to mention in the original post that I am using my outboard Sadowsky pre-amp/DI in to the QSC amp. Link to comment Share on other sites More sharing options...
Members Gregidon Posted November 3, 2006 Members Share Posted November 3, 2006 MY guess is that youare just not driving the input of the QSX enough. Take the pre-amp out (NOT THE POWER AMP OUT) of the SVT and put that into the input of the power amp. See is that gives you suffiecient drive.-greg- Link to comment Share on other sites More sharing options...
Members soul-x Posted November 3, 2006 Members Share Posted November 3, 2006 Originally posted by Gregidon MY guess is that youare just not driving the input of the QSX enough. Take the pre-amp out (NOT THE POWER AMP OUT) of the SVT and put that into the input of the power amp. See is that gives you suffiecient drive.-greg- Yup. The little Sadowsky DI is designed to drive the preamp section of a bass amp or mixer and will provide nowhere near the 1.23V necessary to drive the QSC to full power. The line out on your SVT should be in the right ballpark. Link to comment Share on other sites More sharing options...
Members tonynorie Posted November 3, 2006 Author Members Share Posted November 3, 2006 Thanks to both of you that replied........I'm going to give it a shot with the Ampeg preamp and I'll report back, but what you've said makes perfect sense. Link to comment Share on other sites More sharing options...
Members soul-x Posted November 3, 2006 Members Share Posted November 3, 2006 Originally posted by tonynorie Thanks to both of you that replied........I'm going to give it a shot with the Ampeg preamp and I'll report back, but what you've said makes perfect sense. Bear in mind that doubling your power yields you less than 3db of volume increase -- not much at all. And keep that bridge switch OFF! Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 3, 2006 Members Share Posted November 3, 2006 Yes, you need a preamp, not the DI. Don't bridge that amp or you will be buying new speakers as part of your experiment;) Link to comment Share on other sites More sharing options...
Members DaBender Posted November 3, 2006 Members Share Posted November 3, 2006 Originally posted by soul-x Bear in mind that doubling your power yields you less than 3db of volume increase -- not much at all. People repeat that so much, I guess they believe it. I have a 15 watt tube guitar amp and a 30 watt with twice as many of the same power tubes. There's clearly a huge difference in the capabilities of those two amps to my ears. Link to comment Share on other sites More sharing options...
Members tonynorie Posted November 3, 2006 Author Members Share Posted November 3, 2006 Of course you're all right on both counts.......it worked fine but didn't give me the anticipated huge increase of volumn, so I'm going back to the svt (only). While we are on the subject, and considering that the Hartke 410 is 400w and 8ohms (and the current svt is 275w) , what would be the optimal power output for an upgraded bass amp be? Thank you! Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 3, 2006 Members Share Posted November 3, 2006 Originally posted by DaBender People repeat that so much, I guess they believe it. I have a 15 watt tube guitar amp and a 30 watt with twice as many of the same power tubes. There's clearly a huge difference in the capabilities of those two amps to my ears. You also must realize that in your application, the power amp is often being driven into the non-linear portion of it's operating curve, so effectively apperaing to have more compression and less dynamic range. Link to comment Share on other sites More sharing options...
Members moody Posted November 3, 2006 Members Share Posted November 3, 2006 Originally posted by tonynorie Of course you're all right on both counts.......it worked fine but didn't give me the anticipated huge increase of volumn, so I'm going back to the svt (only).While we are on the subject, and considering that the Hartke 410 is 400w and 8ohms (and the current svt is 275w) , what would be the optimal power output for an upgraded bass amp be?Thank you! Using what you have, you could possibly split the 4 x 10 into two sets of 2 speakers (4ohms a pair) and then drive each pair with one half of the QSC (750 watts per pair - 1500 watts into a 400 watt bin). I don't recommend this, but it's a way of having plenty of power in reserve without bridging (and a good way of killing your speakers if you turn up to high). Maybe consider adding a decent single 15" under the 4-10 for a bit more power? Link to comment Share on other sites More sharing options...
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