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Voodoo Transformer FAQ's

Marshall JMP-1

See Below for Replacement Parts



Question   Do you sell parts to the pubic? Answer: No we do not. Our business model is not set up to support this. 

    Question   What do you recommend running the levels at in order to keep noise to a minimum?

    • Power Amp - We recommend setting the volume controls wide open / full up.
    • Preamp - We recommend using the "Level" control on the front panel as the over all System Master Volume. This should be set to approximately 9:00 to 10:00 for stage volume. The setting varies depending on the wattage of your power amp. 
    • You must also adjust the internal volumes on each patch/channel.
    • Gain Patches - In order to keep noise to a minimum the "Volume" should not exceed 12. Adjust OD1 and OD2 to taste. Setting OD1 & OD2 to 20 will give you maximum gain.
    • Clean Patches - For maximum clean headroom and improved clean tones we recommend setting the "Volume" to 20 and keeping the front "Level" control set lower
    • Clean 1 - Only engage "Clean 1" and set to 12
    • Clean 2 - Engaging "Clean 2" will give you a Mid Boost with added breakup
    • Note - For all other settings please refer to Marshall JMP-1 User Manual 


    New Patch Question   Do you program any new program patches? If so, where are they stored?

    • Yes we program (8) new patches for you free-of-charge. The settings numbers are; 92 - 99


    FX Loop Question   I’m interested in changing the FX-Loop on my Marshall JMP-1 from parallel to series. Is this possible, and if so are there any negatives to doing this? How much would the mod cost?

    • In our honest opinion; The effect loop on the Marshall JMP-1 is less than ideal. For the best results we recommend the following; Go out of your JMP-1 Main Output ---> Into your effects ---> Into your power amp.
    • Note - for best results all instrument and speaker cables should be high quality.


    Stereo Output Question -  I have a stereo power amp that I am using with the JMP-1 to drive (2) speaker cabinets. One output jack of the JMP-1 is going to the left side of the power amp and the other output goes to the right side. Both Level controls on the power amp are full up / on "10" but one speaker cabinet is louder than the other. Why is this and how do I resolve this?

    • Explanation - The "Level" control on the front panel of the JMP-1 controls how much output is sent to the Output Jacks. This control is what is known as a "Dual Ganged" control pot. IE: When you adjust the "Level" control you are simultaneously adjusting (2) control pots.
    • The problem is that both pots on the "Level" control are not matched. IE: as you increase the Level there will be spots where one side is louder than the other. All replacement pots have the same problem.
    • Solution - 1.) Adjust the rig to the desired stage volume. 2.) Use the power amp's Level / Volume controls to balance the volume.


    Data Control Question -  I would like to get the data knob (the component itself - not the plastic knob-cap) replaced – it turns rough and it skips numbers when turning so that it’s difficult to land on the patch you’re trying to select. Can this be fixed / replaced and how much would it cost?

    • In most cases the Data Control can be fixed / repaired.
    • We also routinely stock all proprietary Marshall parts for the JMP-1 preamps and can replace the control if need be.
    • Parts Cost - $49.95.
    • Labor Cost: 
      1.) $15.00 - If we are Modding the unit at the same time as we will already have the unit disassembled.
      2.) $75.00 - As we have to disassemble the unit as well as reassemble.
    • Note - More times than not when the rotary Data control is damaged there are other things that are damaged on the front panel (IE: input jack, etc) so it may be wise to plan on an additional buffer of approximately $25.00. (See below)

    Data & Level Control Knob Question
       Can you replace the actual knobs on either of these controls? If so, what is the cost?

    • Yes and the cost is $5.00 per knob.
    • Knobs may be ordered separately and shipped to you - Shipping & handling charges apply. To order please call 607-256-0465 


    Internal Battery Question   My unit is old and is replacing the battery a good idea? If so, what is the cost?

    • Yes if your battery had not been replaced we advise that you have the battery replaced. 
      Part Cost - $6.95
    • Labor Cost:
      1.) $0.00 - If we are Modding the unit at the same time as we will already have the unit disassembled.
      2.) $50.00 - As we have to disassemble the unit as well as reassemble.
    • Note - If your settings are not saving properly or are reverting to stock factory settings, your need to replace your battery 

    Settings / Preset Backup Question
       I would like to save my internal patches, is there a way you can do this for me? If so, what is the cost? 

    • Yes we can backup your stored settings
    • This is a service known as "Midi Dumping"
    • Process - A spare JMP-1 preamp is required to transfer or "dump" your settings into. Once remaining work has been completed we will dump the settings back into your JMP-1 preamp. 
    • Price for Midi Dump Service $20.00


    Return To Factory Settings   I would like to revert my JMP-1 to factory Settings. How can I do this & will I loose my saved programs/patches?  

    • Warning - Your edited sounds / patches / programs will be lost. if the unit is re-initialized. IE: write your settings down or "midi dump" to a back up unit before proceeding. 
    • How to re-initialize / convert your JMP-1 back to Factory Settings - Hold down "OD1" & "Clean 1" then switch on power switch. Hold buttons until a program patch number comes up on the display.  


    Additional Parts Questions   Do you stock or offer any other parts if my JMP-1 needs repair? If so, where are the prices?

    • Yes we have numerous parts we routinely stock for the JMP-1 preamps such as but not limited to; 
    • "Level" Control Pot (on front panel)   $8.95
    • Input Jack/Nut assembly on front panel   $8.95 
    • Hex Screws (holds top onto JMP-1, etc)  $0.89
    • AC Power Connector   $34.95
    • Midi Jack   $12.95
    • Headphone Jack   $2.95
    • On/Off Power Switch   $10.95
    • Cap for Power Switch   $5.95
    • Stock JMP-1 Power Transformer (not Mercury Magnetics Brand)   $149.00
    • Rack Ear  $34.95
    • Other parts & components available
    • Note - Pricing is subject to change without notice
    • Note - Addition labor charges for installation, etc may apply
    • We do not sell parts to the public. Pricing is provided for units shipped to us for Repair / Mod

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