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Sansamp RBI / QSC or EBS?

Discussion in 'Amps and Cabs [BG]' started by Fangry, May 16, 2002.


  1. HeavyDuty

    HeavyDuty Supporting Curmudgeon Staff Member Gold Supporting Member

    Jun 26, 2000
    Suburban Chicago, IL
    Which part of the original question? :D

    I'd go with the RBI/PLX rig, if it were me...but I'm not you. Which did YOU like better? Can you A/B them?
     
  2. uglybassplayer

    uglybassplayer

    Aug 24, 2001
    New Jersey
    Eh, Not Really :( . Both the QSC RMX & PLX series want a +4dbu signal coming in, while both the SABDDI and the SARBI con only muster at most, 0dbu. It's enough to drive the amp from what I understand, but not enough to really take advantage of it's power. There is a "mod" that factory authorized QSC service centers can do to raise the input sensitivity of the amp (I'm sure Bob Lee can comment more on this, or do a search on the "alt.guitar.bass" newsgroups on "QSC" and "Lord Valve").

    BTW, Here's the email I just received from Lloyd Schwartz, Product Manager for Tech21 in response to my question about this...


    Dear Frank,

    Thanks for you inquiry. The Bass Driver DI can provide up to 0dB output level.
    We've heard similar things about the QSC, but we're not sure if it's entirely accurate.
    We encourage you to contact QSC to see if it's true, or if you can adjust their input sensitivity. The SansAmp RBI rackmount version has the same output, up to 0dB.

    Regards,
    Lloyd Schwartz, Product Manager
    Tech21, New York, New York
     
  3. 810wmb

    810wmb

    Jan 29, 2000
    fgenus - thank you so very much for your post.

    this is what i was afraid of.

    thanks again
     
  4. jerry

    jerry Too old for a hiptrip Gold Supporting Member

    Dec 13, 1999
    I blew my preamp on a gig once, and had to use my Sansamp to power my QSC2402 for the rest of the gig......it got me through the gig, but I could tell it didn't have enough juice to push the poweramp. As for the original question.....to bad you can't get the EBS pre with the QSC poweramp, EBS preamps are very nice!
     
  5. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    At full gain, the RMX 850 and 1450 require about +3.4 dBu (1.15 v) to reach full rated output power at 8 ohms, while the RMX 2450 requires +4 dBu (1.23 v).

    So you wouldn't need a nominal +4 dBu signal; probably something around -7 to -6 dBu (0.346–0.388 v) would be good, and it would give you about 10 dB of headroom for peaks.

    According to Lloyd Schwartz at Tech21, the SansAmp Bass Driver DI puts out a -10 dBu signal on its XLR outputs, but its 1/4" output puts out up to 0 dBu. By removing a resistor, the XLR output can be modified to put out up to +4 dBu. Tech21 can give you the modification info. Contact Lloyd at lloyd@tech21nyc.com.
     
  6. uglybassplayer

    uglybassplayer

    Aug 24, 2001
    New Jersey
    Thanks for checking into this Bob... You Da Man! :cool:

    Peace,


    - Frank.
     
  7. Ehhrrr Bob,


    You mentioned that there is good reason that 1/4" outputs aren't used as much anymore for power amps. Forgive my ignorance, but what reason might that be?

    Cheers rody
     
  8. uglybassplayer

    uglybassplayer

    Aug 24, 2001
    New Jersey
    Most of today's power amps put out quite a bit of voltage through those outputs and 1/4" outs can cause a whole lot of problems...

    - It's far too easy for someone to substitue an instrument cable for a speaker cable. THIS WOULD BE VERY VERY BAD :eek: ! There's a BIG difference between the signal coming out of your bass (or preamp) and the signal coming out of that megawatt poweramp!

    - Because of the way a 1/4" plug is designed, If it pulls out during a gig, it can short the amp as it's coming out (Speakons & Bananna plugs won't do this). Speakons have that "twist and lock" feature, so they're not going anywhere.

    - Even though 1/4" plugs used for speaker cables are usually heavy duty plugs, they still have a "less than" desirable contact area (again, remember that 20 years ago, most amps were somewhere between 100 and 400 watts, today's poweramps can be pushing out THOUSANDS of watts... THAT'S a LOT of voltage going through those connectors!)

    If I remember correctly, by law, amps sold in Europe CANNOT have 1/4" outs for safety reasons.

    My question is... Why are speaker manufacturers NOT adding Speakon (or at least binding posts) to their cabinets? Sheesh, just add another $10-$20 to the cost of the cabinet.

    Peace,

    - Frank.
     
  9. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    Frank said it well. 1/4" plugs and jacks aren't made for high current, and a lot of them (particularly jacks) are downright flimsy, or have become so after years of use.
     
  10. Can you get the EBS-1 with the QSC power amp?
     
  11. uglybassplayer

    uglybassplayer

    Aug 24, 2001
    New Jersey
    I just received an email from Lloyd confirming this. So if I understand correctly, the 1/4" out already has enough output (kind of) to drive the QSC, it's only the XLR out that's padded down, right? I just got a PLX1602. Haven't had a chance to try it with my SABDDI, but when I do I'll report back on how it works with the 1/4" vs. XLR.

    Peace,

    - Frank.
     
  12. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    Yes, that what it appears, from what Lloyd said. I don't own or have access to a Bass Driver DI, so I can't check it. Give it a try, Frank, and tell us what you find. Are you going to try the mod?
     
  13. Jontom

    Jontom

    Mar 11, 2002
    New York
    My old rig was a stereo Qsc (350 watt) amp w/ a Sansamp BDDI(which I modded for rackmount) and an ART tube MP(which brought the BDDI level high enough to drive the power amp). I would go with the RBI and QSC combo. One thing I liked about that pre/amp combo is that it gave me one "really good" tone. And thats pretty much what we are all looking for, right?
     
  14. uglybassplayer

    uglybassplayer

    Aug 24, 2001
    New Jersey
    Bob, I don't know if I'm going to do the mod or not. Probably not if it only affects the XLR because I'll be using the 1/4" out to the QSC and reserve the XLR out for the main board if it's needed. I was just thinking... I have a Crate CA1PD rack mount acoustic preamp that I picked up really cheap a few years ago. Maybe I'll try putting it between the SansAmp and the PLX and see how it sounds.

    I had momentarily considered the "QSC Mod" that Lord Valve talked about in the alt.bass newsgroup, but if I were going to have someone mess around with the electronics, I'd rather do it to the SansAmp.

    Peace,

    - Frank.
     
  15. uglybassplayer

    uglybassplayer

    Aug 24, 2001
    New Jersey
    I found out from Lloyd Schwartz how to modify the SABDDI to bring the level up on the XLR output from -10db to 0db (Note: this should have no effect on the 1/4" out which according to Lloyd, is already at 0db)

    When you remove the back cover of the Bass Driver, you'll see a "black box". Just to the right of its lower right corner (assuming XLR jack is in the lower right hand corner as well), there's a resistor surrounded by two arrows.

    It looks like this: >[]<

    Remove it.

    I checked under the hood of my SABDDI, and found it no problem :D. The resistor on mine had the number "332" stamped on it. NOTE: these are very very (very) small and sensitive components and unless you really really (really) know what you are doing, leave this work to a qualified tech.

    Peace,

    - Frank.
     
  16. Tristan

    Tristan

    Jan 28, 2001
    Ottawa, Canada
    I believe it raises the level to +4db and not 0.
     
  17. uglybassplayer

    uglybassplayer

    Aug 24, 2001
    New Jersey
    If I understood Lloyd correctly, it raises the nominal output to 0db, but by diming the gain control, you can get +4db out.
     
  18. Tristan

    Tristan

    Jan 28, 2001
    Ottawa, Canada
    hot dang! u r correct
     
  19. Bob Lee (QSC)

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

    Jul 3, 2001
    Santa Ana, Calif.
    Former Technical Communications Developer, QSC Audio
    Yup, that's what I infer from Lloyd's e-mail message.
     
  20. geshel

    geshel Supporting Member

    Oct 2, 2001
    Seattle
    So why'd you change? :) What's the new rig?
     

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