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EFFECT LOOP ON SVT 3 PRO - Distortion noise.

Discussion in 'Amps and Cabs [BG]' started by Manuel53R, Sep 25, 2017.


  1. Manuel53R

    Manuel53R

    Sep 14, 2017
    Houston, TX
    Hello guys. I have an SVT 3 PRO. I normally connect all my effects after the bass and directly to the input. Lately, in order to save some room on my pedalboard, I connected my chorus, maximizer and noise gate to the effect loop. I noticed that for some reason, it will boost the amp volume so loud that it distorts the sound horribly. I changed cable, tried different pedals, results are the same. Problem goes away when stopped using the effect loop. Now, this is when playing the gain to the point of clipping (red light clipping) and using the master as main volumen. When using the effect loop, I have to decrease the gain in the amp and play with the master until I get a sweet spot, which is taking away headroom from my amp.

    Anyone here have experienced this issue?. I don't see why the effect loop should saturate the sound that bad.

    Thank you in advance for your feedback.
     
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Is this a series loop?

    Is there a switch or control for make-up gain (instrument to line level) in the loop? If there is, the makeup gain should be turned down.
     
  3. Manuel53R

    Manuel53R

    Sep 14, 2017
    Houston, TX
    There is nothing in the loop that should affect gain/volumen levels. There is just a chorus+maximizer+noise gate. Actually, I tried many pedals and only one pedal and still the same issue. Even the chorus by itself and still distorts as explain.
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Is there a selectable switch inside the amp for setting the send and return for instrument level?

    Some amps had a switch for the send and another for the return, both had to be switched together. Otherwise there would be ~20dB of added gain when the loop was used.

    I don't know if this is the case here.
     
  5. Xandrell

    Xandrell

    Aug 23, 2014
    Sounds like an impedance mismatch. I had the same problem only it wasn't loud enough for a rack effect. I had to insert a line driver and everything is perfect. You have the opposite problem because your pre is all the way up, so maybe a direct box to take it down would be in order.
     
    Manuel53R likes this.
  6. Manuel53R

    Manuel53R

    Sep 14, 2017
    Houston, TX
    Uhm... I did think about it, but didn't know such device existed. I'll look into this for sure, thank you Sir!.
     
  7. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    What happens if you simply connect the effects send to the effects return with a patch cable? This shouldn't cause any problem with excessive gain or distortion. (If it does, there's something very funny going on in your amp.)

    If, as expected, the signal level doesn't change when you patch the send to the return, then your effects must be providing some significant gain. I know from experience that if I overdrive the effects return on my 3PRO, it produces really horrible distortion - no sweet spot between 100% clean and "OMG I broke it."

    Could you be more specific about exactly what make and model the "chorus, maximizer and noise gate" are? I'm going to hazard a guess that at least one of them has some sort of gain or volume control on it.
     
    Josh Kneisel likes this.
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    This was my next suggestion as we try to move down the troubleshooting path. Yes, some of these devices also include input and output sensitivity switches or adjustments (either physical or within software). Ibanez, Roland and Yamaha all used to provide them.

    (There's no use talking about line drivers and such until the actual cause is established.) ;)
     
    Josh Kneisel likes this.
  9. Manuel53R

    Manuel53R

    Sep 14, 2017
    Houston, TX
    This is a boss chorus, BBE maximizer and G decimator. None of this have any gain. I tried each of by itself and the same issue happened. Problem went away when removed everything from the loop. Also I noticed that when using the gain, it goes from a little distortion to distortion hell like around 12 o clock. Something tells me that somehow when the loop is being used, gain gets saturated, doesn't matter what's in the loop.
     
  10. Manuel53R

    Manuel53R

    Sep 14, 2017
    Houston, TX
    I do have other pedals between the bass and the amp, but without anything in the loop, the amp sounds just right. So the "problem" is the loop
     
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Now, you need a tech to look at the levels into and out of the loop, and what may be happening (intentionally or unintentionally) when the loop is not bypassed. There are some loops that contain make-up gain and attenuation for level matching that only function when the loop is in use.
     
  12. The manual for my amps (not an Ampeg) specifically says not to use pedal type effects in the effects loop section.

    The effects loop section is intended to be used with professional rack gear with a nominal input level of 4dBu. Effects pedals should be used in front of the amp.

    Not familiar with that amp..
     
  13. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    This is the very issue that switchable level effects loops attempt to deal with, but there are so many gottchas (like potentially the OP's problem) that it's really not worth the problems. Line level loops are pretty standard in the bass world.
     
    BassmusM6674 likes this.
  14. Xandrell

    Xandrell

    Aug 23, 2014
    Yes, and on my SVT II Pro, it's not line level until the pre amp gain are all the way up, so your limited to that sound to use a line effect. Enter the Lehle Sunday Driver. I can use the amp however I like with the pre down and volume maxed for power tube saturation, even at lower volumes by turning the WA76 output volume down.
     
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    This doesn't solve the problem of overdriving the pedals however. It's only the make-up gain part of the issue.
     
  16. Xandrell

    Xandrell

    Aug 23, 2014
    I know, just replying to the thread on problems trying to use line level effects. The op said he has the pre gain up all the way which could be sending more of a line level to instrument level effects. Just a thought.
     
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Right, but your device won't prevent overdriving of the pedal inputs.
     
  18. Xandrell

    Xandrell

    Aug 23, 2014
    I was suggesting a direct box to bring it down. Would that not work?
     
    Manuel53R likes this.
  19. Manuel53R

    Manuel53R

    Sep 14, 2017
    Houston, TX
    So a direct box like JHS Little Black Amp Box Passive Amp Attenuator won't work?. I have read on its reviews that a lot of people use this to avoid problems like the one I'm having, still I'm not sure it it would work. For the record: i didn't know of the existence of this prior this post.
     
  20. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    It will work provided there's transformer isolation that brings the level down along with the output impedance. THEN, there's the need for an adapter that's wired so that tip goes to pin 2 and sleeve goes to pin 3 tied to pin 1. The whole thing is kind of kludgy rather than just using the pedals as intended in front of the amp.
     
    BassmusM6674 likes this.

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