Deluxe memory man mod

Discussion in 'Effects, Pedals, Strings & Things' started by Rossl, Jan 10, 2008.


  1. Rossl

    Rossl Member

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  2. analogmike

    analogmike Gold Supporting Member

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    The newer ones may not have IC sockets so changing chips may not be easy. See my FAQ for more info on the DMM and changing chips in them and other mods and tweeks.

    Here is a free DIY mod for 2008!


    !!! DONT TOUCH ANY OTHER TRIMPOTS !!!

    If you have the new RELAY TRUE BYPASS version with two wires on the switch, this procedure will help get rid of the CHUGGING white noise you sometimes hear. If you don't have that problem then you probably don't need to do this unless you are getting distortion from the pedal.

    In the center right area of the board is a trimpot #7. It is above TP4 and TP5. If this does not match up with your board DON'T DO ANYTHING as you may screw it up if you adjust the wrong trimpot.
    If it does match up, mark the current setting of #7 with a sharpie in case you want to set it back. It's usually horizontal or vertical.
    Turn up (clockwise) the #7 trimpot to LOWER the gain of the pedal, until the noise stops. You can turn it up all the way if needed. It will also reduce the distortion you get on the repeats. But you will need to turn up the level knob on the pedal to get the same effect level. It should be turned up so the OVERLOAD light just comes on.

    Good luck!!!
     
  3. SonicVI

    SonicVI Member

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    I changed all the NE4558's in my early 80's DMM with TL072's as well as changed the 100K input resistor with a 470K and it made very noticeable difference.

    I think the input resistor swap made an even bigger difference than the opamp swaps. I used to get a lot of distortion on repeats but this helped it a lot and made everything clearer and easier to setup as far as the input gain and blend knobs go.

    It was posted over at diystompboxes.com a while back.

    "Now, the stock input impedence is really low and there's a ton of potential gain on tap - much more than is needed, even using the DMM as a boost. So replace the 100K resistor in the input with a 1M pot. Here's the schematic: http://www.freeinfosociety.com/electronics/schemview.php?id=381.

    The stock gain structure has a 100K resistor before the opamp and a 1M pot in the feedback loop (this is the volume pot). By changing the 100k resistor to a 1M pot, you can set it to the stock impedance and when the volume pot is on full, have 10x gain. But you don't need 10x gain, and the stock impedance is really low and loads down the pickups in a passive guitar (particularly with single coils). Put in the 1M pot and you can raise the input impedance and lower the overall gain available, finding a balance between a higher input impedance and still having enough gain on tap. I liked the input pot set to about 500K, which still had enough gain (2:1 at max though I didn't use it on max) for a nice boost. Really improved the sound and gave it more depth."
     
  4. bribrigingo

    bribrigingo Member

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    I did it in my older non-true bypass DMM and it made it sound a lot smoother and cleaner while still retaining the analog feel.
     
  5. Strat

    Strat Member

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    hmm..who can repair (?) these things. Mine makes really really bad screaming noises if I plug it in anymore. thanks
     
  6. analogmike

    analogmike Gold Supporting Member

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    Howard Davis is the man for repairs.
     
  7. Rossl

    Rossl Member

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    Is there anyway to mod the blend function? I like to blend the dry sound with the echo. IMHO there is a very small range that I can use with the stock blend pot.

    For me to have the option of echo/repeats ONLY is a waste.
     
  8. SonicVI

    SonicVI Member

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    You could probably replace the pot with a log (or reverse log) taper pot so that the 50/50 blend point is no longer in the middle.
     
  9. Rossl

    Rossl Member

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    Sonic are you referring to the same 100K resistor when you say you changed it to 470K and installed the 1M pot? I assume you used the 470K to equal the pot set to 1/2 of it's limit.

    My unit has a 100K resistor, but it does not have a 1M (from input to ground NOT the pot) as shown in the schematic. Mine has a 2.2 meg. I assume the 2.2M would also raise the gain.
     
  10. SonicVI

    SonicVI Member

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    The 1M from input to ground is a pull down resistor to prevent the footswitch popping. Maybe sometimes they use a 2.2M. But you want to change the 100K with either a 1M trimpot wired as a variable resistor or a fixed value resistor somewhere between 100K and 1M. I initially used a pot and found that about 500K worked well so I put in a 470K. The lower the resistor the more gain you have and the higher the less gain.
     

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