Rig questions: QSC PLX 1202 into Genz Benz Uber 4x10

Discussion in 'Amps [BG]' started by damon78, Nov 30, 2012.


  1. damon78

    damon78

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    I've been playing bass since I was a kid but have mostly performed professionally on guitar. I'm just getting in to the finer points of bass amplification as I gig more and more on bass.

    I had a QSC PLX 1202 for a PA and managed to get a wonderful trade on a Genz Benz uberbass 4x10. I am running it in bridge mono mode currently and I think I should be getting more volume. I have been testing it with the direct out from my Trace Elliot combo since an svp pro I got on ebay was defective and had to go back.

    I gigged with it all summer using guitar rig as my preamp (terrible, I know). Now I'm looking into tube pres and am looking at an Alembix f1x, a bbe bmaxt, avalon u5 or ampeg svp pro. I have also been looking at svt pros since they can sometimes be had for not much more than the preamps.

    I play in an zimbabwean rumba group, but want something versatile for other gigs as well. I am into more classic tones, reggae and soul, less hifi, Bass and low mid heavy, James Jamerson, Family Man, but I also want the ability to have a variety of sounds for different gigs. I also have an alternative rock gig where I go for brighter, growlier sounds with a p bass.

    I play a 1993 American jazz bass deluxe with tape wound strings, a 1990 cp thornton 5 string (neck through 3 bartolinis, aguilar onboard pre) and a 1992 Mexican traditional series p bass with Bill Lawrence p bass pickup.

    So, my questions. Which preamp and why? How can I get more volume out of my system? Will I get more volume by adding a second cab and running my power amp in stereo? Different speaker combination? Will two smaller cabs be better a 1x12 and a 2x10 for example? Are the power amp and uberbass a good foundation for my rig? Any other pres I should be considering?

    Needless to say all this is on a musicians budget. Thanks in advance for any knowledge you can drop on me.

    Here's the specs for the qsc:

    http://www.qscaudio.com/products/amps/plx/plx.htm
  2. CL400Peavey

    CL400Peavey Supporting Member

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    At either 8 or 4 Ohms you have enough power to push any 410 into obliteration. I would be curious as to the level of signal you need versus what you are getting from the DI out.

    As far as Pre's go, I would check out the Monique.
  3. damon78

    damon78

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    Nov 30, 2012
    Thanks for your response

    The Uber Bass is 1000 watts power handling, so should be fine. I thought it might be low signal from my DI, when I turn up more, can gently clip the power amp but I think I'm clipping the pre as well, because it sounds like garbage (clippy, farty). I guess I'll have to wait till I get a proper preamp to test some more.

    Thanks for the reccomendation on the monique, looks like a beautiful piece of gear, but what I'm looking at is in the $2-600 range on the used market and the Monique seems out of my price range at this point.
  4. CL400Peavey

    CL400Peavey Supporting Member

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    That is the thermal rating of your cab, which has little to no correlation on how much power it can take before it farts out. A 410 is going to be limited to about 500 watts before it starts to fart out. I suspect you are reaching the limits of your cab if you are hearing what you describe.

    Its a very nice piece, and gets great reviews. Out of my price range right now as well.
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  6. damon78

    damon78

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    It's just that I want to be able to kill babies with my rig, you know? So if the cab is maxing out then a second cab for bigger gigs is the way to go?
  7. craig.p

    craig.p Supporting Member

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    Enable the subsonic filters on your power amp and set them for 50 Hz, not 30 Hz. That'll a) clean up your bottom end, b) give you significantly more headroom, and c) go a long way toward protecting those G-B drivers from overexcursion. That cab is tuned very high and needs those 50 Hz high pass filters enabled at all times.
  8. damon78

    damon78

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    Craig p: thanks that seems to have cleaned things up a bit for sure and good to know about the speaker needing it. I had been cutting some of the lowest band on the eq as well, which I noticed helped.

    So if the 4x10 really can only handle 500 watts should I not turn the power amp over 12 o'clock? Bridge mono should be 1200 watts.
  9. craig.p

    craig.p Supporting Member

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    Common misconception. Volume controls aren't limiters. They only control the gain of the amp's input stage. There's no way to set that amp to limit at X watts output.
  10. damon78

    damon78

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    Then am I way overpowering the speaker?
  11. craig.p

    craig.p Supporting Member

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    I'd say yep, that's probably what's going on.

    You've also got the limiters on that power amp enabled, right?

    Farty sound can also be caused by pickup height too high. Most of the advice you read on setting pickup height is dead wrong. Drop your pickups 1/8" from where they are now and see if that improves things.
  12. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio!

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    The gain controls don't restrict the power that the amp can put out. They only affect the overall gain (not the input) of the amp--i.e., V out = V in × gain.
  13. damon78

    damon78

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    I see, but Genz Benz claims the speaker is 1000 watts RMS is that just BS?

    And thanks for the pickup height tip, I'll check it out.
  14. CL400Peavey

    CL400Peavey Supporting Member

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    I would be looking to add a second cab, or to pick up a bigger cab.

    There are very few cabs out there that can really handle everything your amp is swinging bridged (read: your volume concerns are not the amp). If you need more volume then you need more cab. Adding an identical cab will net you around 6db or so of volume.

    Personally for what you describe as your tonal goals, I would be looking at a different cab all together.
  15. CL400Peavey

    CL400Peavey Supporting Member

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    Its a thermal rating, not a "fart out rating".

    Most of the commercial manufacturers do this, the spec is generally meaningless.
  16. damon78

    damon78

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    And what would you recommend in terms of cab/combinations?
  17. CL400Peavey

    CL400Peavey Supporting Member

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    Really depends on how attached you are to your current cab.

    If you were buying what would your budget look like, and where are you located?
  18. damon78

    damon78

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    I'm not at all attached to my current cab, I just got it because it was a good trade.

    As far as budget goes, I'm limited to my preamp purchase this month and would probably need to sell/trade some gear in order to buy any cabs. The Uber Bass is in great condition so if I got rid of it that would net maybe $800 which I could put in to new cabs. I have some other gear I need to put up for sale/trade as well.

    I'm located in Maine.
  19. CL400Peavey

    CL400Peavey Supporting Member

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    I would get your pre amp straightened out. I would check out a Aguilar Tone Hammer pedal actually. Great little DI pedal that can drive an amp. Might be your cup of tea.

    As far as cabs I would check out the link in my sig. Go to the greenboy forums and look at the map on the bottom of the page, I would look for a fEARful user. Here is a lit of cabs I would look into, they may or may not be your cup of tea but there is a lot of info about them:

    fEARful 15/6
    fEARful 1212/6
    fEARful 15/6 + 15sub
    fEARful 1515/66
    fEARless 215
    greenboy Dually

    There are a few users playing similar styles of music to you. They have had great results with a 15/6 + 15sub set up.
  20. bgavin

    bgavin Supporting Member

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    I own the PLX-1202, and it is a keeper.
    The input sensitivity 1.0 volt for maximum output.
    Each channel produces 40 volts (200w) into an 8-ohm load.
    At 4 ohms, each channel produces 36 volts (325w).

    Most of the noise is made by the first 100 watts.
    200 watts is only +3dB more, and this is a negligible increase.
    Many real-world drivers can't tolerate large input power without exceeding xmax.

    If you have a typical 4x10 that is wired in series-parallel, you can use the PLX-1202 to get a noise boost by using both channels.
    Add a second Speakon jack to the cabinet and wire a pair of 10s in parallel to each jack.
    This makes your cab a 2x10 + 2x10 in two channels.
    You also avoid wiring all four in parallel, and the resulting 2 ohm load.

    The advantage of all parallel wiring takes full advantage of your maximum voltage output.
    Applying 40v across a series pair only gives 20v (50w) to each 8-ohm driver.
    36 volts applied to a parallel pair is 162w per 8-ohm driver.

    Alternatively, you can use the 1202 for bi-amping with an active crossover.
    Lows to CH-1 and Highs to CH-2.
    You should have a rack for the 1202 anyway, so a modest 4RU rack will allow a preamp, active crossover, and the PLX-1202.

    Enjoy.
  21. agedhorse

    agedhorse Development Engineer-Mesa, Product Support-Genz Supporting Member

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    Hold on a minute, there's some inaccurate information being stated as fact when in fact it is anything but an incorrect assumption.

    The mechanical power rating on the uber 410 is not 500 watts. With any reasonable high pass filtering if is probably closer to 800-900 watts (rms). In fact it was designed specifically to be driven to the maximum rated output of any of our 900 watt (rms) amps and still be within the mechanical limits. The thermal rating is over 1000 watts rms

    Secondly, the likely problem that's responsible for the farting sound (in this specific case) is that the Di out on the amp is likely not able to deliver enough clean drive signal to the power amp. Also. Is the limiter engaged on the power amp? It certainly should be.

    A 50hz hpf is much higher than necessary, a 40hz 3rd order bw hpf is fine and a 35hz 4th order bw filter is even better and more transparent.

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