Home › Forums › Help/Technical Questions › Changing the imput impedance on the DMM

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  • November 5, 2010 at 3:16 am #80948
    Kekke466
    Member

    I have a Re-issue memory man in the big old casing (5 buttons, true bypass) from the 2000’s.
    I recently was checking out how I could decrease the overload problem with my Epi Riviera that has pretty hot humbuckers. I guess that would be to change the input impedance right?

    I have quite some knowledge of stompboxes but the DMM is far out of my league.
    Could anyone confirm that to change the input impedance, you have to increase the R2-100k ohm resistor or am I looking at the wrong one there.

    (I tried to change R2 with a 1M pot but the results were weird)

    thanks a lot for help.

    November 5, 2010 at 3:21 pm #112412
    julian
    Moderator

    What I’d do would be to add an Audio Taper potentiometer to trim the input signal. Take the wire from the input jack, put it to the right lug of the potentiometer (If you are looking down at the potentiometer from the top and the lugs are facing you.) Then add a wire from the middle lug to where the input wire originally went. Then add a wire from the remaining lug to ground.

    BTW, there is an adjustable gain on it, and if the overload light blinks a little bit I don’t think it’s a problem.

    November 5, 2010 at 3:50 pm #112413
    Kekke466
    Member

    Wouldn’t that be more or less the same as just putting a “volume” pedal before the DMM or cutting back on the volume pot on the guitar?

    November 5, 2010 at 5:12 pm #112415
    julian
    Moderator

    Yes, essentially it would be the same thing, but I know it’s not always convenient to roll back on your guitar volume or on a volume pedal immediately after switching an effect on.

    November 6, 2010 at 1:05 am #112422
    Kekke466
    Member

    That’s right, thanks for the tip I’ll try it out tomorrow.

    November 6, 2010 at 1:47 pm #112425
    Kekke466
    Member

    I’ve been thinking about this potmeter at the input jack. If I would put it there, wouldn’t it affect the bypass signal as well? In other words, I think it should be after the relay, not at the input jack? Eventually this might create a little volume drop, when the effect is engaged. But at least it won’t overload so bad, I hope.

    November 7, 2010 at 3:52 am #112437
    Kekke466
    Member

    To my conclusion, it’s actually better to just increase R2 (the resistor before the opamp U1) just a tad. Definetly not with a 1 Meg pot. More like a pot of 250k ohm and that will work alright and has a nice range. At least for my guitars it has.

    November 11, 2010 at 6:46 pm #112522
    Howard Davis
    Member

    Increasing the input impedance alone can reduce tone sucking, but not the overdrive distortion problem. My Input Impedance Increase plus Hot Pickup mods will bring up the headroom, which is what is needed most.

    If interested in mods for your DMM, email me privately at howard.davis2@att.net

    Howard Davis – designer of the DMM.
    Guitar pedal design engineering, repairs, and custom mods:
    http://howardmickdavis.com

    November 11, 2010 at 8:25 pm #112524
    Kekke466
    Member

    I’ll contact you in time.

    The pedal has emptied my wallet quite a bit for now…

    April 7, 2011 at 10:46 pm #114934
    Kekke466
    Member

    Howard’s mod did it all! It sounds perfect with humbuckers now. I loved this pedal with all my heart but after Mr. Davis his modifications this pedal has it all. Incredible, my most favourite delay pedal can handle hi gain pick ups without trouble and seems to sound even better with single coils.

    Thanks again!

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