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Volume Loss Help

Discussion in 'Amps and Cabs [BG]' started by non, Dec 3, 2019.


  1. non

    non

    Aug 4, 2015
    i have a ampeg ba108 practice amp that has a issue that might be impedance related.
    the amp has a aux input. if i put a pedal in the fx loop and turn the pedal on the volume from the aux input drops really low.
    if i turn the pedal off the aux input level get loud again. i have tried different pedals in fx loop with the same result. i have tried different things in the aux input ie. laptop. mp3 player, drum machine and the volume still drops with the pedal in the fx loop is on.
    any ideas what is going on?

    thanks
     
  2. abarson

    abarson

    Nov 6, 2003
    Santa Cruz
    Sounds abnormal. What does Ampeg say about the situation?
     
  3. Wasnex

    Wasnex

    Dec 25, 2011


    The schematic for the amp can be found here. https://ampeg.com/support/files/Schematics/B Series/BA110/BA110 [NEW] Schematics.PDF

    Note the Aux In is connected at the Effects Return. When you plug a pedal into the return, the output impedance of the pedal is loading down the Aux In signal.

    FY, The Effects Loop on this amp is line level so it's not really suited for an effects pedal anyway. Pedal typically operate at instrument level.
     
    non and agedhorse like this.
  4. non

    non

    Aug 4, 2015
    thanks for the schematic. i see that now.
    why would the effects loop not be instrument level?
     
  5. Because a lot of folk use rack mounted effect units of various kinds that are all line level. Put your effects where they should be - in front of the amp.
     
    Wasnex likes this.
  6. Wasnex

    Wasnex

    Dec 25, 2011
    From what I have seen, the majority of effects loops are line level.

    The problem you are having would seem to be a bit of a design flaw IMHO, but I believe the amp is work as it should.
     
    non likes this.
  7. Because it is between the preamp, and the power amp. Therefore, already boosted to line level for the power amp's use.
     
    non and agedhorse like this.
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The majority of effects loops are line level because:

    1. The effects loop is a place to insert a line level device (there are some line level pedals but most are instrument level)

    2. The effects send on many designs also becomes a line level preamp output that can drive an external power amp.

    3. The effects return can be used as a power amp input that takes its signal from a line level preamp output. Almost always, when plugging into the return, it breaks the link between the effects send and effects return jacks.
     
    non and Passinwind like this.
  9. non

    non

    Aug 4, 2015
    thanks for the replies everyone.
    so would it hurt anything if the instrument level pedal in the fx loop is on and to just crank the volume all the way on the aux in devices so they can be heard?
     
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    You would probably overdrive the pedal as it's expecting instrument level whichi s much lower than the loop level.
     
    Wasnex likes this.
  11. non

    non

    Aug 4, 2015
    what i was trying to do is i am getting real boomy bass and the amp eq cannot get rid of the offending frequency so i set the amp eq flat and use a multi band eq pedal in the fx loop to solve the problem, which it did. but then i am getting the volume loss as i described.
     
  12. non

    non

    Aug 4, 2015
    that would explain the loud hiss when the pedal is engaged.
     
  13. Wasnex

    Wasnex

    Dec 25, 2011

    Yes, typically you either over drive the instrument level pedal or have a poor signal to noise ratio.
     
    agedhorse and non like this.
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Time to study up on gain structure...
     
    BassmanPaul likes this.
  15. non

    non

    Aug 4, 2015
    as a pedalboard aficionado i am aware of gain structure. i have never had a need to use a fx loop so i was not aware the loop was line level.
    thanks all for the lesson. i learned something today.
     
    agedhorse and Wasnex like this.
  16. Sometimes things work and sometimes they don’t. Time to try a new tack. :)

    Perhaps a rack mount EQ in the Loop will do what you need.

    Edit: I have a suitable one on a shelf in my garage if you’re anywhere near me.
     
  17. non

    non

    Aug 4, 2015
    this is just for my little "bedroom" practice amp and space is limited but i appreciate the offer.
     
    BassmanPaul likes this.

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