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Output levels: Demeter preamps driving QSC power amps

Discussion in 'Amps and Cabs [BG]' started by lo-freq, May 27, 2003.


  1. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    Have any of you that use Dem's and QSC's had to adjust the internal adjustment for the overall gain level to get it to fully push the QSC?

    Just curious; got a new bass rig last Friday and won't be gigging it until this Thurs.
    [I have a 201S & PLX1602 (bridged).]
     
  2. The 201s should be WAY enought to push the 1602.
    The Dem has and internal gain adjustment inside the box. Demeter sets it at 12:00 and claims that should be right for most applications. If your not sure give them a call and ask for James. Depending on your bass you may need to boost is some. If your not clipping you should be fine. To my knowledge, if turned UP, all that would do is let you cut back on the volumn knob. I think you said you were running it at 2:00 on your other post. I do prefer the PASSIVE input over the active with both my active and passive basses. I play Laklands and the active does not have that strong of an output so the the Active input on the Dem is the way to go for me. The passive sounds good too, but I have to turn it up, and playing live I like the Active better.

    You'll probably not like this to much, but I would have gone with a bigger amp for more options. (sorry) Even stead fast Demeter and Bergantio user like Jerry Buyers (Aloha) upgraded to a 3002 for more headroom without bridging. He does not like to bridge either, like me. Hope I quoted him right. Hi Jer! Not telling you to get another amp (like you would do what I say..) your 1602 should work just fine, you just might have to turn it up a bit. The HT322 craves power. Hope this helps. Enjoy your new stuff!
     
  3. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    Thanks for the input.

    I am not sure I'm following what you're saying about the power amps (other than bridging vs. non-bridging). The PLX3002 in non-bridged mode has 900W @ 4 ohm. The PLX1602 bridged has 1600W @ 4 ohm (more than even the 3402 when it's not bridged).

    I went with the 1602 with the 322 because I believe that any venue that exceeded their output should have its own rather serious PA support, in which case I would be turning the system down to only use it as a stage monitor.
    If I had a 2402, I would be bridging it also, but I think that the 1600W will do fine given the 104db sensitivity of the 322.

    I am confident in what I have, I just had read about issues with driving QSC's with some preamps and so wasn't sure if any adjustments might be needed to the internal gain control.

    No worry mate. All is cool!
     
  4. g4string

    g4string Supporting Member

    Sep 19, 2002
    Melissa, TX
    I am the guy with HPB-1 and 1602 who responded to your previous thread. I run my 1602 bridged as well. I have my 1602's volume at about 3/8 and the HBP-1's volume at about 7/8. I adjust my over all volume from my bass (active Lakland 55-94). With my rig setup like this the power meter from the 1602 flashes up and down from the green band into the yellow band. I have never seen it flash into the red (clipping), only into the lower/middle half of the yellow band. This tells me that my HBP-1 is driving my 1602 correctly. The 201 and HBP-1 are pretty much identicale, exept mine has a parametric eq while yours does not. All in all, you should not have any problems. BTW, running my amp at 4 ohms I have not had any problems with thermal shut down or anything like that.
     
  5. Well, I wasn't sure I should even mention since I'm far from and authority. Your comparisons are accurate. The extra just gives you more "head room", and that is a good thing. By having a bigger amp you get more power from the stero/parallel mode and still have another channel just in case. Plus, you can run cabs with different impedance and control them independently. "more options" As I said your 1602 will be killer. I have just learned there is never enough power, but watts = $ plain and simple. I keep trying my 2402 bridged, but always go back to the single modes.
    Note: Bridging is always harder on equipment even if it is designed for that type of constant operation. At least that is what I hear and read repeatedly. Chow!
     
  6. Can you clearify "3/8 and 7/8" Does that mean like percent or between 3 and 8 and 7 and 8? Thanks
     
  7. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    Thanks g4string. Looks like you have your preamp really cranked. Sounds like I should be OK, though. The HT322 is in the ballpark efficiency wise to a pair of GS112 with a bit more power handling capacity.

    I'm playing a StingRay 5 into mine and keep the volume all the way up, controls fairly flat--a little treble and midrange cut and a smidgen of bass boost, PU selector on single coil.

    Thanks Big String. At my bridged power and actual playing output level, the 1602 should be just loafing along 98% of the time, so I don't think I'll be stressing the amp. Bottom line, yeah, it's just a headroom thing.

    I'll let you guys know how it goes "live" after this weekend.
     
  8. GrooveSlave

    GrooveSlave

    Mar 20, 2003
    Dallas, TX
    I do prefer the Active input over the passive with both my active and passive basses.

    Can you elaborate on why? I just got a Demeter HBP-1 and I'm still experimenting with it.

    I must say that it seems pretty hard to get anything but an awesome sound out of this thing. I love it. :D
     
  9. I'm using a 201s not the HBP. I'm glad you caught that. I said it completely backwards. I actually use the Passive because it's not padded. I like it because my bass is punchier and more present in the Passive input. I think I need a nap...
     
  10. marc40a

    marc40a

    Mar 20, 2002
    Boston MA
    I been running a Dem VTBP201 (the older 1 1/2 space model) into a PLX1602 for years w/ no problems. 100's of gigs of all sizes.
     
  11. jerry

    jerry Doesn't know BDO Gold Supporting Member

    Dec 13, 1999
    Hawaii
    I've had no problem pushing any of my QSC poweramps with the 201! Great combo!....IMHO:cool:
     
  12. jokerjkny

    jokerjkny

    Jan 19, 2002
    NY / NJ / PA
    that's the one thing i hate about the Demeter line. wassup with putting the gain inside the housing?

    also, another niggle was that my Stewart was very sensitive to what the Demeter was putting thru it. dunno if mine is faulty in some way, but i cant seem to put the Dem's volume knob anywhere over 3, before i get some mild distortion. works fine with EVERY other power amp i've used. very annoying.
     
  13. g4string

    g4string Supporting Member

    Sep 19, 2002
    Melissa, TX
    Big String,

    The fractions I used was the percent, or level of my volume nobs. So on my QSC the volume is set below the half way mark (3/8) and my Demeter's volume is almost wide open (3/4-7/8). Hope that helped.
     
  14. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    3/4 of all the way up is not too bad, but my 201S starts hissing some above that level (I have my 1602 cranked a bit more than yours).

    Do I have a noisey tube? [Or is that normal?]
     
  15. g4string

    g4string Supporting Member

    Sep 19, 2002
    Melissa, TX
    I do not think a hissy tube is normal. I would contact James Demeter and tell him whats going on. He should ship you a new tube.
     
  16. I have not had any signal to noise ratio issues. I usually turn the gain or gains on my QSC all the way up and set my Dem active input on 1/2 (12:00) if I use the passive input on about 11:00.
    I'm not bridging, but in parallel mode. Sounds good to me. I think several others use this method too. QSC people like the hotter pre signal and amp gains set at "what you need." Bergantino people like the amp gains all the way up set the input signal just under clipping level. I've spoken with both manufacturers. I don't think one opinion is necessarily more correct than the other, just different. Both will work fine and everyone's tastes and signal chain may differ.... :)

    My Dem201s is quiet as can be.. might be a bad tube or cord or connector or floresent light or maybe a snake on the loose..:eek:
     
  17. jerry

    jerry Doesn't know BDO Gold Supporting Member

    Dec 13, 1999
    Hawaii
    I peg the volume on my QSC's too, and the Demeter is about 9-10 o-clock. I don't have to pluck too hard and let the poweramp do the work;)
     
  18. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    jerry,

    do you use the active input with your active basses on the Dem?
     
  19. jerry

    jerry Doesn't know BDO Gold Supporting Member

    Dec 13, 1999
    Hawaii
    I use the active, but I have used the passive for grins from time to time;) For my main rig I use a PLX3002, so I have plenty of headroom.
     
  20. Jerry J

    Jerry J Supporting Member

    Mar 27, 2000
    P-town, OR
    I have the older 1.5 space 201 going into the PLX1602. No problem here. I also prefer to have the PLX pegged and adjust the Demeter or the Alembic F-1X to taste. So since I now have the two Bergantino HT112's I'm in the Bergie camp.:)