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Ampeg SVT3 Pro PREAMP OUT Balanced or Unbalanced? NEED A DEFINITETIVE ANSWER QUICK!!!

Discussion in 'Amps and Cabs [BG]' started by BassYerFaceoff, Dec 19, 2018.


  1. Ok, I have looked and searched everywhere I could think of and (unless I missed something) I cannot find a definitive answer. Yes I have looked at the manual and No it does not say. (Only mention is the DI)

    The reason I'm needing to know is because I JUST ordered a Crown XTI 1002 (I plan on running in bridged mono) into a Schroeder 212pl 1200W rms using the SVT3PRO as a pre amp... I JUST realized that the CROWN has an imput impedence of 1.4v with BALANCED XLR inputs ONLY. *EDIT* Gig in TWO days! (Will receive on gig day!) Need to run my cab AND FOH using DI.

    HELP.
     
    Last edited: Dec 19, 2018
  2. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    Maybe I'm missing something. What is preventing you from using the XLR from the SVT to go into the Crown?
     
  3. My understanding is that it will have a low input/output sensitivity (voltage) compared to the Preamp out. The input sensitivity on the Crown is 1.4v the Ampeg DI output... unknown. Plus DI is usually a weak signal meant to feed into a PA MIXER. Yes it is balanced but I want to get the best balls out of this. *EDIT* Sorry but I also need to run DI to FOH along with cab.
     
    Last edited: Dec 19, 2018
    Mistahbenn likes this.
  4. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    Keep in mind, as I understand it, the tube gain section is AFTER the preamp. So you won't be getting that part in the preamp out. That 12ax7 and 12au7 (I think I'm right on the second one.... it's been a long time since I owned mine) are used to drive the power section (MOSFET maybe?). There are 2 or 3 more 12ax7 tubes in the preamp section.

    So, to me, it won't really be the sound of the SVT III through the cabs running it into a power amp straight off the preamp. It'll sound fine. But it just won't have the grit you could get through cabs otherwise.

    Keep in mind, I last owned one in the late 90s. So I could be remembering incorrectly.
     
  5. You'll still get the preamp tube sound (and grit) through the gain. The power amp tubes are a non factor in my question and not to sound short and sound like a d×$k... but that wasn't my question. Sorry but Happy Holidays.

    Does someone out there know PLEASE?!
     
  6. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    Ha! Not offended. Good luck with this. Wish I could help.
     
    BassYerFaceoff likes this.
  7. Jazz Ad

    Jazz Ad Mi la ré sol Supporting Member

    The manual looks pretty clear to me. It doesn't give dBu levels but since you have a knob to control it you should be fine.

    The schematics show that the preamp out is unbalanced. upload_2018-12-20_3-14-55.
     

    Attached Files:

    ctmullins and BassYerFaceoff like this.
  8. Thanks... DOES Anyone know if the "PREAMP OUT" not the DI or "Transformer Balanced Line Outputs" on the AMPEG SVT3 PRO is balanced or unbalanced?
     
  9. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    Preamp out is unbalanced, just a phone jack. I'm not sure what the signal level is like, I've never used that on mine. You could try an adapter cable (TS phone plug to XLR), it might be hot enough to drive the power amp.

    Line out is balanced (XLR or TRS phone jack) but I don't think you'll get anything near 1.4V out of it. I've run mine into a board and as I recall it's closer to a mic level than a hot line level.

    Get yourself a small mixer to put between the line out and power amp in. It should solve the problem and you'll find lots of other uses for it ;)
     
  10. Do you know if using the adapter from 1/4" to XLR from the "PREAMP OUT" would in effect, make it a balanced line into the power amp. If it does I'm sure it'll be hot enough.
     
  11. Jazz Ad

    Jazz Ad Mi la ré sol Supporting Member

    No it wouldn't. You're making this a lot more complicated than it needs to be.
     
    PaulJSmith likes this.
  12. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    A balanced input just uses the difference between the two signal lines. If you're sending a balanced signal into it, the two signal lines have the same signal, just opposite polarity (positive on one, negative on the other).

    You can connect a single-ended signal to the balanced input, one signal line is the signal and the other is ground (no voltage). You lose the noise canceling benefits of a balanced line (usually not a big issue for a short cable run), but it works just fine.
     
  13. Jazz Ad

    Jazz Ad Mi la ré sol Supporting Member

    You also lose level doing that, in the range of 1/sqr2.
     
  14. okcrum

    okcrum in your chest

    Oct 5, 2009
    Verde Valley, AZ
    RIP Dark Horse strings
    That might be so for power, but it's simply 1/2 for voltage. It's the same (6dBv) as the voltage decrease you'd get by unbalancing (grounding one side of) a balanced output to feed an unbalanced input.
     
    Jazz Ad likes this.
  15. InhumanResource

    InhumanResource

    Dec 28, 2012
    There's no power amp tubes in that amp. Power amp is solid state.
     
    Spectre Gunner, kobass and bhoff5150 like this.
  16. Jazz Ad

    Jazz Ad Mi la ré sol Supporting Member

    Yes and no.
    Power comes from MOSFET, so solid state but the power section is driven by a preamp tube that plays a role in the tone of the amp as a whole.
     
    PaulJSmith and BassYerFaceoff like this.
  17. What HE "Jazz Ad" said.

    What do you mean?
     
  18. InhumanResource

    InhumanResource

    Dec 28, 2012
    Yes, but as you said the power section is MOSFET. I usually hear the tubes you're talking about referred to as "driver" tubes. I use the 6-PRO which is the same amp with a bigger power section and there sure aren't any power tubes in it.
     
    Gearhead17 and bhoff5150 like this.
  19. OK I'M confused (My first time using a Preamp and Power amp).

    So will using a 1/4" on the "PREAMP OUT" with an XLR INTO the "XLR IN" Be BALANCED or UNBALANCED?
     
  20. I want to use THE AMPEG SVT3PRO "PREAMP OUT" (Preamp tubes, the POWERAMP on the SVT IS NOT USED) ... I'm not going to use THE POWERAMP ON the SVT... That's why I bought the CROWN POWERAMP...
     
    Last edited: Dec 19, 2018

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