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Multiple effects loops connection efficiency: GK Plex into GK MB500

Discussion in 'Effects [BG]' started by Plectrum72, Feb 3, 2017.

  1. From send of pre-amp into return of amp

    3 vote(s)
  2. From output of pre-amp into return of amp

    5 vote(s)
  3. From send of pre-amp into instrument input of amp

    0 vote(s)
  4. From output of pre-amp into instrument input of amp

    0 vote(s)
  5. Other

    0 vote(s)
  6. Carrots

    2 vote(s)
  1. Plectrum72

    Plectrum72 Supporting Member

    Trying to figure out the best way to connect my GK Plex to my GK MB500 to get the most out of the GK Plex's voicing options. Bonus if there's a way to connect the two and be able to quickly and easily swap between Plex pre-amp and the MB500's pre-amp in a live setting between songs, but for now I'm content to swap between the Plex's 800RB voice setting and the MB800 voice setting.
  2. fasto


    Mar 4, 2007
    Amsterdam, NL
    sorry, i voted carrots because i really don´t know, BUT your question(s) is interesting and i subb´d this thread to find out. I guess GK + GK is not GK anymore.
    Plectrum72 likes this.
  3. Plectrum72

    Plectrum72 Supporting Member

    All the minutia TB obsesses about and only fasto and I are interested in this? Is there a TB thread discussing this already (regardless of brand) that my Google skills failed to dig up? TB to Plectrum72, "Your Kung Fu is weak."

  4. fasto


    Mar 4, 2007
    Amsterdam, NL
    There is a huge GK thread in the amp-section of TB, maybe a better place to ask?
  5. Swimming Bird

    Swimming Bird

    Apr 18, 2006
    Wheaton MD
    Well, I know nothing bout this GK business. But I had experimented with something like this with my VTBD and Ampeg PF-350. The VTBD was waaaay too hot and I kept triggering some sort of shutoff function on the PF. Going out of the VTBD into the effect loop return of the PF solved the problem and made the rig louder and clearer by bypassing the PF preamp.
    Plectrum72 and BadExample like this.
  6. BadExample


    Jan 21, 2016
    Effects Send/Return are usually line level, so I voted #1. #2 might work. Going into the instrument input will probably be a very hot signal and hard to control. I retract this statement: You can try all and see what happens, just bring the (knobs affecting volume) up slowly from 0.

    Not recommended to try #2 or #3, but I expect going directly into the instrument input of a preamp from the output of another preamp will result in going from 0 - 60 way faster than you would like, making it very difficult to control well and could be noisy. I have never tried it; it might work, especially if you can dial down the output of the pedal preamp. I usually use junk earbuds rather than a cab to test when doing such shenanigans, so save the speaker, and I don't put them in my ear... on the table or in hand inches away from my ears!

    If you have an active bass, you could use a simple "Y" cable to split the output from the bass to both the instrument in on the integrated amp (head) and the instrument in on the new pedal preamp, then go with #1 (or #2 if that works better for some reason), which should disconnect the pre in the head from the power amp when the pedal is plugged into the fx return on the amp. This way, unplugging one jack enables the integrated preamp and plugging it in enables the pedal preamp.

    The thing to remember with a "Y" cable is you can safely split an output into two inputs, but you must not combine two outputs into one input. This is why the return on the amp disconnects the internal preamp, so you don't combine two outputs (causing smoke, popping, springs snapping etc. :D ).

    BTW: I glanced at the manual when you first posted and did not see it stated that this protection is in place, however I have never heard of an integrated amp effects loop that does not disconnect the preamp. It is very easy to test if you want to verify, just plug you bass in, get some sound going, mute it and plug just one end of a patch cable into return, unmute and verify the bass goes silent. Then mute and plug the other end into send (so you loop effects send to effects return externally), unmute and bass sounds should be amplified again. If the amp is old, you may find that this exercise "breaks" the switch in the loop and it gets noisy or won't work at all unless you leave the patch cable in place. That just means you discovered a problem that was lurking... dirty or tarnished switch in the send jack. Better you find it now than it fails when you are headlining for ZZ top! You can "fix" it with a patch cable or properly clean the switch (no spray and a tiny bit of deoxit... if you don't already know). I would also say, the effects loop is not a safe play to play with a "Y" cable, unless you are absolutely sure of what is going on and that it is safe for your gear.

    With a passive bass, you may not have enough signal to split it passively with good results. Passive bass will depend on the output (pickup) impedance and the input impedance of both preamps, so it is unpredictable without facts and math and other yucky stiff :D It's easier to just try it.

    I have rambled and covered a lot, not intending to say you don't already know much of what has been said. Absolutely no disrespect intended brutha!
    Last edited: Feb 5, 2017
    Plectrum72 likes this.
  7. BadExample


    Jan 21, 2016
    I really don't see preamp to instrument in working well. Maybe if it can be tuned down at the first preamp. If you hit a shutdown/protection mode trying it, I retract my suggestion that it might work. I've hit my preamp with a pretty hot signal, but never line level. It could in fact be unsafe to the preamp.
    Plectrum72 likes this.
  8. Plectrum72

    Plectrum72 Supporting Member

    Alrighty, after much experimentation this weekend with and without a band setting, I have concluded that the effects send of the pre-amp (GK Plex) into the effects return of the amp (my GK MB500 and rehearsal space Ampeg SVT 450) offers the cleanest signal path and least complicated tone control (probably strongest signal too).

    I also tried the pre-amp out into the effects return of the amp which resulted in a noticeable drop in volume and a hiss.

    Last I tried the pre-amp out into the instrument in of the amp, essentially using it like any other pedal. I obtained similar results to the pre-amp send into the amp return; however, there was more coloration due to two pre-amps and tweaking two sets of EQ controls to achieve the best (for me) sound proved to be more complicated. The signal noise (when not playing) was more noticeable as the volume/gain was cranked on the pre-amp pedal.

    Thanks BadExample for reminding me to start each time with all volumes at 0 to prevent inadvertent speaker damage.

    TLDR: Pre-amp send (GK Plex) into amp return (GK MB500 and Ampeg SVT 450) yielded the best results.
    BOOG, BadExample and Ricky Caboverde like this.
  9. Ricky Caboverde

    Ricky Caboverde Supporting Member

    Feb 26, 2004
    Miami, FL
    Thanks for the update!
    BTW, did you mean to say "TLDR: the FX send (GK Plex) into amp return..."?
    Last edited: Feb 6, 2017
  10. Plectrum72

    Plectrum72 Supporting Member

    Yes, that is exactly what I meant to say. Thanks for the clarity.
    Ricky Caboverde likes this.

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