Need Help - Need to Revese the Phase in Effects Loop

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by somedude, Jul 2, 2004.


  1. somedude

    somedude Member

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    I'm having problems with my parallel effects loop.

    The two signals are blending out of phase with each other, so the closer I get to the 50/50 wet/dry, the quieter it gets. There's also alot of cancelation going on, which makes the amp tone go to sh*t on the dirt channel.

    How would I be able to fix this problem?

    Thanks.
     
  2. John Phillips

    John Phillips Member

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    I'm assuming setting the FX mix on the amp to 100% doesn't work - it doesn't with some amps, eg Mesa, it only gets to about 90%, and that allows enough dry signal though to cause trouble.

    There are some possible solutions:

    #1 - convert the loop to series.

    #2 - replace the effect unit with something similar that doesn't reverse the phase.

    #3 - get a box to reverse the phase again.

    That's assuming it's definitely a phase problem. If you're using any digital effects, it could be a latency problem though. This will sound quite similar, and it means that #3 is not an option. If the FX unit has a Mix control, you could set it to 100% effect, but it might still not sound right unless it's something where the dry and effect parts are fairly well separated - like a delay.

    I went for #1 on my Mesa, BTW.
     
  3. somedude

    somedude Member

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    #1 - convert the loop to series.

    My setup has both a parallel and series loop. I tried using the series loop and I don't particularily like the tone I get without the dry signal; putting the whole signal through the effects seems to sterilize it in some way.

    #2 - replace the effect unit with something similar that doesn't reverse the phase.

    That might be an option, but it's my last resort.

    #3 - get a box to reverse the phase again.

    Where do I find such a box? Or specs to build one?


    The gear in question is a Mesa Recto Preamp (Mix only goes to 90%) and Mesa 2:100 power amp. The problem is a EXH Small Clone. I've tested it in other loops (all serial unfortunatly) and it works fine. The only thing I have left to try is reversing the phase.
     
  4. somedude

    somedude Member

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    Anyone?
     
  5. spaceboy

    spaceboy Member

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    well, i THINK he means just another effects unit - one that would reverse the phase in the same way as the Small Clone... ooh! you could use another Small Clone. that could be cool.

    or maybe he does mean some strange, special phase-reversing dooda...
     
  6. somedude

    somedude Member

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    A friend of mine is sending me his Small Clone to test that very theory with. I'm tempted to turf it and replace it with something else, but I love the sound it makes, and I'm not interested in droping over $200 on a Anolog Man clone (yet).

    The thing is, I know what I need. It's an amplifier that's designed to output at the same level it inputs (unity gain), and since it's an amplifier, it inverts the phase when it amplifies the signal. The problem is, no one knows were to find one, or can tell me how to build one......

    .....I keep hoping an amp tech or audio engineer of some sort will read this thread.....:(
     
  7. spaceboy

    spaceboy Member

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    ohhh, well, my Higher Technological Studies training tells me that an Op Amp in Inverting Amplifier configuration with a gain of 1 (the feedback resistor and input resistor must be equal) would do it, but obviously that would introduce nasty solidstate-ness into your signal, so you'd want a small preamp with a single triode tube... well, are all preamp tubes Duel Triodes? whatever, you'd just want to run the signal through a single triode and again, somehow configure it with a gain of 1... but we never looked at valves in Tech Studies... :rolleyes:

    It'd be simple enough with an op amp though. i think...

    John? help! :D
     
  8. somedude

    somedude Member

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    Would running an opamp really kill the tube tone? Considering it's already running though a solid state chours pedal.......


    Besides, I'm running it in a parallel loop, so there's still the uneffected dry signal.....
     
  9. spaceboy

    spaceboy Member

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    very good point.

    EDIT: and if it does suck tone, just get yourself a nice buffer

    EDIT II: and keep me posted on how that 2nd Small Clone works out :)
     

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