Markbass effects loop conversion

Discussion in 'Amps [BG]' started by Zonked, Feb 17, 2013.


  1. Zonked

    Zonked

    Joined:
    Jul 12, 2010
    Location:
    Los Angeles
    I've been looking through the threads. It's just too much unrelated info, and just haven't quite found the answer. Anyway, I want to plug my Eden WTX-264 into my Markbass LMIII's effect return for times when I am craving the Eden tone with a little more watts. I know the LMIII effects return is shipped parallel from the factory( comes after the eq),so I think it's best if I I convert to loop to series. My question is, can I do this conversion myself? Is it easy enough? Thanks in advaced.
  2. B-string

    B-string Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    Yes I remember a thread showing it is a simple jumper change (one or two) inside the amp. The jumpers are just like computer hard drive jumpers, lift off and reinsert in optional position.
  3. figuredbass

    figuredbass Supporting Member

    Joined:
    Jul 11, 2007
    Location:
    NYC vicinity
    Yes, and as B-string said. However, there a few important things to note before trying to do this on your own:

    1. Markbass considers the jumper changes to be something only an authorized Markbass service center is authorized to do, and not a user-serviceble action. So though it is possible and easy for you to do it yourself, proceed at your own risk as they may not repair the amp under warranty if you make a mistake and damage it.

    2. It is still possible to use the effects return input for the purpose you described with the jumper still set to parallel mode. What parallel mode simply does is mixes the signal from the LMIII preamp with the signal that's plugged into the effects return - think of it like a two channel mixer. The only possible consequence of doing it this way is a drop more noise than the series mode, which is already negligible, but can be even further reduced by turning the LMIII input gain knob down all the way when you use this setup. The advantage of doing it this way is that you don't have to change anything inside the amp, and you still have the LMIII preamp available with its own gain knob for a second instrument or whatever.

    3. The effects return is definitely pre EQ and NOT post EQ (including the VLE and VPF), whether set in parallel or series mode. So it is not simply a power amp input since the EQ follows it. However, with the 2 filters down all the way and the 4 EQ knobs set to 12:00 the EQ is virtually razor flat in frequency response and no "voicing" will be applied to the signal you plug into the effects return. This is actually a good thing because you still have the option to apply finishing touches with the LMIII EQ if you ever need to.
  4. Zonked

    Zonked

    Joined:
    Jul 12, 2010
    Location:
    Los Angeles
    Hmm, thanks for the useful info guys. I am off to a gig now, but I it looks like I will have to experiment with out the modification first and see if I get the desired results. Has anyone here done effects loop parallel to series conversion on the LMIII themselves?
  5. B String

    B String Supporting Member

    Joined:
    Apr 11, 2002
    Location:
    Los Angeles
    For me it didn't do jack. I wanted to use the amp to double on upright bass. With most amps I use, I can get a whole other sound for my upright bass using the effects loop and another preamp. On the Markbass amps I've owned it doesn't matter where the jumper is, you're still going through the preamp section on the amp. I don't like it.
  6. murphy

    murphy

    Joined:
    May 5, 2004
    Location:
    Toronto, Canada
    Yeah...not an amp to use as a poweramp option.
    you can never get away from the Markbass sound
  7. Zonked

    Zonked

    Joined:
    Jul 12, 2010
    Location:
    Los Angeles
    Yeah, looks like I'm going to have to look at other options then. Thanks everyone.
  8. enjoi1018

    enjoi1018 Supporting Member

    Joined:
    Apr 18, 2011
    Location:
    Auburn, AL
    Hey guys, for some reason I'm not able to start a conversation with the member who I think has the instructions on how to do this mod... does anyone know where the thread is or PDF? I've been searching for days. TIA!
  9. enjoi1018

    enjoi1018 Supporting Member

    Joined:
    Apr 18, 2011
    Location:
    Auburn, AL

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