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MXR Dynacomp and Phaser Volume Drop and PBC Buffers

Discussion in 'PBC General Discussion' started by sjgam, May 11, 2019.

  1. sjgam

    sjgam
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    Guitar to either MXR Dynacomp or Phaser out to amp directly with no PBC - no audio volume drop.

    If I put either in loop 7 (which is fed directly from buffer 2) of PBC then again no audio volume drop. I am assuming both pedals must have impedance requirements that buffer 2 is meeting.

    If I put them in any other loop including loop 1 in front of buffer 1, then significant volume drop.

    Whats so special about loop 7 and buffer 2?

    My other pedals are ok volume-wise in any of the loops and I am ok leaving the phaser in loop 7 to take care of its volume drop issue but I need a loop for the dynacomp without volume drop. (Again loop 1 with buffer 1 feed still volume drop)

    Any thoughts on how to resolve and whats happening here?
     
  2. rjmmusic

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    It is an impedance problem, but it's probably on the pedal's output, not the input. Are any other loops turned on when you're trying these tests? And, are you sure the mono/stereo buttons are set correctly? (If you're running all loops in mono, both buttons should be in the IN position.)
     
  3. sjgam

    sjgam
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    Thanks for reply - Replies to your points/questions:

    1. It is an impedance problem, but it's probably on the pedal's output, not the input.Strange that Loop 7 only with Buffer 2 in front of it fixes it though? How does one match an output?
    2. Are any other loops turned on when you're trying these tests? No just the loop that the dynacomp or phaser is on. Should I be trying with the loop/pedal on after the pedal?
    3. And, are you sure the mono/stereo buttons are set correctly? (If you're running all loops in mono, both buttons should be in the IN position.) Yeah double checked that. I only have mono pedals. What would be the audio effect if one or both was out (out of curiosity).
    BTW - are you surprised putting them in loop 1 with buffer 1 on did not resovle it but loop 7 with buffer 2 on does?
     
  4. rjmmusic

    rjmmusic
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    Some older pedal designs have higher output impedance, and they need a high impedance input after it, or they'll lose volume. Most likely something after the pedal has a low impedance that the pedal's output can't handle.

    If the Mono->Stereo (out) button was in the Out position and you had mono effects in loops 7-10, you would end up with little or no signal, because it would be shorting your signal to ground.

    When you're moving the pedal from loop 1 to loop 7, are you moving the cables with it, or are you using different cables in each loop?
     
  5. sjgam

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    Yeah I have all 10 loops cabled out to 10 pedals and all the pedals are fine except these two.

    So when I swap them I am just moving the pedals, not the cables, just to establish its not the cables. And the pedal that gets swapped (e.g. Boss CE2) works fine on the loop and the cables the mxr was on.

    And again these two mxr pedals work fine on own - guitar in and out to amp directly and they both work with no volume drop in loop 7.

    But not the other loops.

    I tried turning each of the buffers on and off but no effect and I keep them all on. I tried parallel and series with PBC mixer feature in loops 7-10 and that did not help.
     
  6. rjmmusic

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    But, does the MXR work when you move it to another loop in the same group, for example, loop 2? It's a common occurrence that a cable can have a partial short, which still works fine with low impedance output pedals, but has problems with pedals with higher impedance outputs.
     
  7. sjgam

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    i moved the two mxr pedals to several different loops but only removed the volume drop on loop 7. And they both work directly input from guitar and output to amp without PBC. But let me check again with other loops one more time.

    Question - if output impedance on these two mxr pedals is the issue, with the PBC hooked up, what impedance is the pedal seeing when only its loop its engaged. Is it seeing the amp impedance or one of the buffers depending on the loop number. And if I turn on loop after it, does it see the impedance of the pedal after it? Trying to see what impedance its seeing with PBC connected.

    Another thought - I have a Boss RC-2 looper between the PBC output and amp (did not need it in loops) - perhaps when only one loop is activate the output of the pedal is seeing the Boss RC-2 impedance and causing problem? I can take it out and see what happens.
     
    #7 sjgam, May 12, 2019
    Last edited: May 12, 2019
  8. rjmmusic

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    If buffer 2 is on, it will see that when sitting in any of loops 1 through 6. It will also see any impedance issues in its output cable.

    Do you have an ohmmeter? That would help figure things out.
     
  9. sjgam

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    You were right - cables had a "partial short" - made new cables and put the mxr pedals in their same loop where I want them and volume level is back to normal on both when engaged

    I got thrown off because other pedals swapped into same loop and cables were working and went down the buffer and mxr impedance analysis rabbit hole. Well I learned about impedance and buffers in the process :)
     
  10. rjmmusic

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    Yeah, it happens, I have similar conversations pretty frequently. :)
     

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