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My amp hates buffers - why?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by trumpus, Jan 25, 2008.

  1. trumpus

    trumpus Supporting Member

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    I finally got around to firing up my whole pedalbord through my BF'd SF Vibrolux Reverb. After spending some time wiring everything just right, I noticed that every pedal placed after a buffer emits a loud "pop" when engaged. I am currently running about 10 pedals, the majority of which AFTER a Doobtone MicroBuffer2.

    I also tried going guitar > Antelope MDEQ (with buffer on) > amp and there's a pop when the MDEQ is engaged. When I go Timmy > MDEQ > amp or just Timmy > Amp, no pop!

    Is there a particular reason why my amp doesn't like buffers? Has anyone else had this issue with SF or BF amps? I just had some work done on it and it is in tip top shape otherwise! Any thoughts?

    Brian
     
  2. trumpus

    trumpus Supporting Member

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  3. phsyconoodler

    phsyconoodler Member

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    i'm not an effects expert,but is not the purpose of a buffer to boost or correct the signal before it goes into an amp?If you use the buffer before the effects it seems logical that the buffer does nasty stuff to the effects before they enter the amp.
     
  4. Lyle Caldwell

    Lyle Caldwell Member

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    How are you powering the pedals?
     
  5. trumpus

    trumpus Supporting Member

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    My understanding has always been that optimal placement of a buffer was at the beginning of a long run of effects (ie, lots of cable before the amp). I thought placing it after effects, but before the amp misses out on the ability of the buffer to negate signal loss in long runs of cable.

    I'm using a Godlyke Power-All and a Visual Sound One Spot, with a total of 3 daisy chains. Some pedals are powered individually. The same setup does not have ANY noise or popping issues when I run it through my Mesa Boogie DC-3.

    Brian
     
  6. Lyle Caldwell

    Lyle Caldwell Member

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    I suspected a Powerall or Onespot.

    Those are both switching power supplies, and can be problematic (even damaging) with many buffers, as many buffers these days use DC pumps to get higher internal voltages.

    Mario at Axess warns against switching supplies with his BS2, and I have the same warning going into the Lavaflow manual.

    Try guitar > buffer > Timmy > amp with the buffer and Timmy being powered by batteries or a Boss adapter.

    You're correct about buffer placement.

    If that's not the issue, then you have a ground loop between the order of effects and the order in which your pedals are powered. This might be exacerbated by some DC leakage in pedals (though I doubt in the Timmy).

    Remember, when you try guitar > Timmy > amp you are eliminating potential ground loops caused by other connected audio devices on the same daisy chain.

    And in the buffer > Timmy vs Timmy > buffer example, you changed the audio path but probably did not change the sequence in which they are daisy chained.
     
  7. trumpus

    trumpus Supporting Member

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    Interesting - any idea why this isn't a problem when using the same setup through my Mesa DC-3?

    Also, I think there is some confusion about my actual setup. The Timmy/Buffer thing was part of a little experiment to figure out what the popping was associated with. My pedalboard (and the reason I use a buffer) looks like this:

    Guitar > TB loop (Tuner) > RMC3 > Doobtone microbuffer2 > Tonepress > Deja Vibe > KOTv4 > Eternity > Blue Boy Deluxe > Tim > Analogman Delay > DL4 > Amp

    I've been using a simillar setup for a while through the Mesa without any noise issues. I recently swapped out my MDEQ for the Doobtone because of space The power supply has been the same for the last 2-3 years. I will try to plug in to different parts of the pedalboard to see if bypassing the buffer gets rid of the popping. If not, I'll start breaking it down and seeing which pedal (if any) is the culprit. I just can't figure out why this is an issue with the Fender and not the Mesa?

    Is there something about the older BF circuit that needs to (or can be) modified to fix this? I'd hate to have to ditch the buffer all together!

    Brian
     
  8. Lyle Caldwell

    Lyle Caldwell Member

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    Old Fenders have truly lousy ground schemes. If the input jacks are loose or dirty, all kinds of crap can happen.

    Also, does your Fender still have the two-prong power cord? If so, see if the popping occurs when the Ground switch is set to one side, but not the other.
     
  9. trumpus

    trumpus Supporting Member

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    The amp's got a 3 prong cord and just had a thorough once-over by a local, well respected tech (who happen's to favor the VR's and takes a special interest in them).

    I noticed today that it happens with both amps, but more signficantly with the Fender. It even happens with my Analogman delay, which doesn've the typical 3DPT switch. I tried bypassing some effects and it is still noticeable. I also noticed that when I step on pedals or jostle the cords, there is a scratching or whooshing sound. It happens to all of them. They are all George L and relatively new.

    Could it really be the power supply? I'm currently using 1 Voodo Labs One-Spot an one Godlyke with a total of 3 daisy chains (2 on one supply and one on the other) to power the following:

    RMC3
    Doobtone microbuffer2
    Tonepress
    KOTv4
    Eternity
    Blue Boy Deluxe
    Tim
    Analogman Delay
    DL4
    Tuner

    Some of the power plugs are not used. I power my DejaVibe from it's own supply. Should I power the Line 6 from it's own supply? I've got the original Line 6 supply around somewhere?

    How can I tell how many mA each pedal draws and how many the power supplies give?

    Brian
     
  10. davidp158

    davidp158 Member

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    FWIW, I find that some pedals and amps simply don't "play well" together. I don't know if its an impedance thing, order of pedals in the signal chain, true bypass switching, or built in buffers. My non-technical bias is that you have to try combinations to find out what works and what doesn't. Pedals that sound great with one amp may sound horrid with another. This is compounded by the number of pedals, their order, the guitar and amps in use, power supplies and cables. Everything effects everything else do some degree.

    Buffers can help a lot, but one buffer circuit may work better with some gear combinations than others. I use a Demeter Fat Control only for its buffer, and like it very much. I also have an Axess BS2, but feel the Demeter works better with my particular pedals, guitars and amps. A lot of players love the BS2, so I'm holding on to mine to experiment further. As I understand it, buffers change the high impedance guitar signal to low impedance. Thus, some pedals may not deal with this change as well as others. You don't have to put the buffer before all your pedals to gain some benefit from it. Invest some time in trying it at all possible locations, and you might find one that works, or isolate a pedal that conflicts with the buffer.

    Ten pedals is a lot of pedals, so you might consider using a true bypass switch strip (even if your pedals have true bypass switches). The switch strip will allow you to activate specific pedals and keep the others out of the signal path. They are also a great tool for comparing pedals and diagnosing problems like this. The buffer in the MDEQ may be all the buffering you need. Some times the "pop" sound is just static electricity that's built up in the pedal, and can go away after working the switch a few times.

    good luck,
    Dave

     

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