FX loop help

Discussion in 'Effects, Pedals, Strings & Things' started by Woody777, Feb 7, 2008.


  1. Woody777

    Woody777 Member

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    I have a Mesa Boogie Tremoverb with a parallel FX loop (I can set the mix level to 100%, making it more or less a serial loop). It also has a knob on the back that can bypass the loop, turn the loop on, turn the loop on for specific channels, or set an external switch (i.e. footpedal) to turn the loop on/off.

    I like the ability to turn multiple chains of effects on/off with one stomp. I use a combination of effects that should go both in front and in the FX loop. I use a volume boost (MXR Micro Amp) that defeats the purpose when not in the FX loop. I use only distortion from the amp. When the loop is on (even with no pedals), the tone sounds worse then with the loop bypassed.

    I'm trying to set up my rig. Here's the options I have so far (I'm open to changes and/or new ideas):

    1) set the FX loop to external switch
    - best compromise for quality of tone
    - use a footswitch to turn the loop on/off
    - the effects bleed through if a pedal is on but the loop is off
    - corrected the problem with one of these:
    [​IMG]
    - but now I get a huge volume drop

    2) set the FX loop to always on
    - worst quality of tone
    - true bypass looper to toggle FX chain on/off

    3) set the FX loop to off
    - best quality of tone
    - all pedals run in front of amp
    - time-based effects suffer

    Any other ideas? I'm stumped!
     
  2. pgissi

    pgissi Member

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    Its simply an Impedance converter and although there may be a way to get it to work, it may degrade tone. Since I am not 100% familiar with it I cant say there isn't a hack possible but for what purpose?

    Hum elimination or Impedance conversion, with either of these goals, its the wrong device for a guitar amp

    The Ebtech device achieves signal Impedance conversion using a high quality audio transformer which when used in your amps fxloop, is decoupling your pre-amp output from the power stage, your creating an insertion loss, converting where there is no need.

    Your basically starving your amps output stage

    It is not capable of gain the output section needs from the pre-amp, only Impedance conversion via induction that takes place in the audio transformer.

    Go here and read the applications guide-
    It states its intended purpose is to convert the unbalanced -10dbu line level signal found on consumer grade gear to balanced +4dbu gear that is found on pro gear and do this in the reverse also.

    Although the guitar fx loop is compatible with a line level signal processor, in this case the conversion through the audio transformer is the showstopper since the amount of gain possible in a guitar amp fx loop cannot be realized through the transformer.

    Its simply is a voltage converter and the voltage conversion is of a fixed nature due to the transformer itself-
    from the ebtech page
    The Line Level Shifter™ uses the physics of
    inductance and impedance matching to
    increase or decrease the signal voltage
    without the added noise of active
    electronics.


    By using it in your loop, your introducing additional inductance and impedance properties not found in the amp and that are not necessary or beneficial.

    Have you heard of anyone using it this way, I would be curious to here about it?
     
  3. Woody777

    Woody777 Member

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    Thanks! That all makes perfect sense... at least the parts I understand :jo

    I talked directly to Mesa and they said the problem with the effects bleeding through was due to the fact that the FX loop was at +4 (pro) and my pedals were at -10 (consumer). They recommended the Ebtech device. They said they have never used it, but I should give it a try.

    So I called Ebtech, explained the situation, explained what Mesa said and they said the product will work.

    Obviously, it didn't. I think either Mesa fed me wrong information (not likely, they are absolutely great) or I misunderstood what they said (more likely because I don't get this stuff).

    Anyway, I "solved" the problem by just leaving the FX loop on all the time. My tone suffers slightly, but the effects sound much better in the loop than out front.
     
  4. pgissi

    pgissi Member

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    I
    I am baffled that it was recomended and I just dont see how transformer coupling would work in an effects loop. The only way to achieve coupling of 2 different impedances as its desgined to do and do without active processing is using a transformer.

    Going back to your orginal problem-

    The Tremoverb manual is linked below, it has a feature called Loop Active Master, from the manual "when its LED is illuminated, the Loop Active Master replaces the Channel Masters to become the overall Master Volume Control this is in addition to the channel masters becoming a balancing control and an fx send level control" it continues " the Loop Active Master then becomes an FX return control..."

    WOW, this is the creme de la creme of loops

    I am not 100% sure but looking at the Trems manual I see a fairly complex Loop design and the instructions on page 9 of the manual is the key to making the loop work as it should with the ket point that setting it to 50% is unity and maybe assuming that 100% mix is a proper setting, may be part of the problem. If unity is found at 50%, 100% may be too much boost.

    I would read and reread this to get a better understanding of setting the levels, anytime you have more gain stages with level controls, balancing issues are common.

    the manual-
    http://www.mesaboogie.com/manuals/Tremoverb.pdf
     
  5. Woody777

    Woody777 Member

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    The 50% at unity part... are you talking about the mix knob or the send level? I keep the send level just past 50% for unity gain, but I keep the mix knob at 100% to act like a serial loop.

    I will experiment today with setting the mix knob lower and see what it does.
     

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