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Ampeg SVP-PRO Noise Gain Structure Question

Discussion in 'Amps and Cabs [BG]' started by 12bass, Jun 2, 2003.


  1. Hi Everyone!

    I've seen many posts talking about the SVP-PRO and how noisy it is. I've owned one of the original black-face units since 1998, and haven't found it to be any noisier than the preamp section in my Eden WT-500, that is to say that I find it quite reasonable in terms of noise production.

    So, this leads me to wonder how people are setting up their gain structure. Are a lot of people running the Master wide open and adjusting the output volume with the input Gain? This would certainly be a lot noisier than adjusting the Gain control until the LED just lights, and adjusting the output volume with the Master.

    I've noticed several people say that the Drive control doesn't do anything on their SVP-PRO, and I have to wonder if they aren't using enough Gain to engage the Drive section. If you use enough Gain to light up the Peak LED, you can get lots of Drive if that's your thing. It's hard _not_ to notice!

    I always suggest to run as much gain as possible at the input of a preamp, of course allowing for headroom, and adjusting volume at the output. This always gives you the best signal to noise ratio (more signal/less noise). If you crank the Master wide open and don't use enough Gain, don't be surprised to hear a lot of noise!

    or maybe I just have a quiet SVP-PRO.....
     
  2. With mine just out of the box, I hooked it up to a power amp with no input. When I turned up the power to full, It made a very loud hum like a ground loop.
     
  3. With my SVP-PRO, I will admit that I can hear the power transformer hum acoustically, but there is very little hum or hiss that comes out the signal output.

    Then again, I usually run my SVP-PRO into my Eden WT-500 and use the Eden's Master to adjust the overall volume. Have you tried running the Ampeg at a higher setting and lowering the gain on the power amp?
     
  4. Not only do I do that, I also use a noise gate between the pre and power amp. It's plenty quiet enough for club work. My gripe is that for $500 bucks it should be as quiet as most other pre-amps. I'm gonna have my tech work on it when I get some time off. My guess is a crappy tube.
     
  5. David Wilson

    David Wilson Administrator Staff Member Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    Exactly. I tried a brand new one earlier this year. I loved the sound, but I got problems with really bad hiss. I could probably live with it grudgingly for live use, but for studio use I don't see how it could be usable.

    And yes, I was adjusting input gain to maximise gain at that stage and adjusting master volume for output volume adjustments.

    As GreyBeard says, for $500 I expect more.
     
  6. submelodic

    submelodic

    Feb 7, 2002
    Seattle, WA
    That's exactly my problem as well.
     
  7. boogiebass

    boogiebass

    Aug 16, 2000
    Yup, I was in the same boat. I managed to solve it (sorta) by turning down the power amp gain. This pre has so much output gain that it wasn't a problem. Burning in the tubes for 24 hours supposedly can make a difference but I dunno. I'm trying it anyway. I'll post the results.
     
  8. Just wondering, I have a SVT-3 Pro: If I would crank the gain on it together with the 'tube drive' knob, would I get usable distortion?
    (I know the Tube Drive knob is something else than the SVP-Pro's Drive button, but still...)
     
  9. thetaurus

    thetaurus

    May 28, 2002
    Muncy, PA
    i bought a used svp pro, and i haven't had any problems with any kind of hiss or obnoxious noise. more than anything, i hear the fan from my power amp. i keep the gain about to where the red light comes on, maybe alittle more. then i usually control the overall volume by combining the master on the preamp, and the gain on the power amp. i've not have problems with hiss. it could be solder joints though, because i've heard that's a problem. maybe i just got lucky. mine is an older one.
     
  10. ibanezroadster

    ibanezroadster

    Apr 9, 2012
    The problem everyone is discussing is with out a doubt a earth problem. What the issue is a potential difference in your earth between the preamp and the power amp. What verified this to me was the guys who use the di output don't suffer from this hum. This because there is a isolating transformer between them and the signal. All you need to fix the issue is to purchase a good quality. and lots of car audio stores stock them. A good Earth loop isolator and use this between the preamp and the power amp. Problem solved.
     
  11. My SVP-Pro is a 2003 model, factory stock:

    V1 - Groove Tube GT12AX7C
    V2 - Groove Tube GT12AX7C
    V3 - Groove Tube GT12AX7C
    V4 - ElectroHarmonix 12AU7A/ECC82EH
    V5 - ElectroHarmonix 12AX7E

    It does not hum or hiss.
    As noted above, the DI balanced out is not as hot as the preamp unbalanced out.
    I played mine all night last night with the unbalanced out connected to a PLX-3002.

    I set the Gain control to barely light when I really pounded on it, the Drive to zero, the GEQ disengaged.
    This setting produced very rich and clean grand pianos, baritone saxes, and various Hammond sounds.
    The unbalanced out has far more Moxie than is required to drive the PLX-3002 to full power.