How do I find the milliamps of a pedal?

Discussion in 'Effects, Pedals, Strings & Things' started by s360guitarist, Dec 21, 2009.


  1. s360guitarist

    s360guitarist Silver Supporting Member

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    (This may be a dumb question, but I am pretty sure that I have done that before.)

    When buying a pedalboard power supply, some say each line will handle 100 or say 200 milliamps. Where is the best place to find out what the pedal needs/puts out/etc.?

    I have looked online for a couple of my pedals and its just not there. Any guidance to be given here?

    Thanks!
     
  2. Akridosity

    Akridosity Member

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    They should show it on the manual.
     
  3. torquil

    torquil Member

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    If you don't find the info anywhere, you can measure it yourself:

    Put a 1ohm resistor in series with the battery in the pedal, and measure the voltage difference across the resistor, in volts. The resulting number will be the amount of current going through the pedal, measured in amperes.

    Or, if you have a current meter, connect it in series with the battery. No need for a resistor in this case. Many DMMs have a current meter built in that will work for such small currents.

    - Torquil
     
  4. blackba

    blackba Supporting Member

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    You can also contact the manufacturer of the pedal and get the specs there as well.
     
  5. StompBoxBlues

    StompBoxBlues Member

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    It's the right info, but just to expand on it...

    All volt-ohmeters I know of also measure current (but as you say, maybe very little). The main thing is you usually have to move the probes into the meter when you measure current, and select current (select the biggest number and move down from there) and you have to "insert" the probes serially in the circuit.

    This just means:

    1) Move the one probe (the red one usually) over to current measurement.
    2) take the battery clip off of one side of the battery, and use one probe on the battery, the other on the clip where the battery would normally connect.
    3) read the meter.

    I think this info (plus many readings from different pedals) can be found on the "stinkfoot" site that Leonardo mentioned in his post. Stinkfoot did a great job of collecting actually measured currents for most pedals out there. Also he has described the way you measure better than I have here.

    In my, and Stinkfoots' experience, the named current on the data sheet, even when included for a pedal, are often WAY off with reality. Some pedals I think use more current when on, and when you actually play the guitar...
     
  6. peridot1

    peridot1 Member

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    Every pedal I bought says it on the power supply. That is if yours came with one.
     
  7. WailinGuy

    WailinGuy Member

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    The milliamps number on the power supply only tells you the maximum rated current that it is capable of. This is almost always larger than the current the pedal actually draws, often WAY more. For example, a typical pedal might draw around 20 milliamps at 9 volts, but 9 volt wall wart power supplies (such as Boss PSA120) are rated for 200 ma or more.

    Another thing to keep in mind -- any pedal that has a status LED will draw more current when it is engaged than when it is bypassed, since the LED draws some power when its lit. (The main pedal circuit remains powered whether or not the pedal is bypassed.) So if you take the trouble to measure the current yourself, be sure to measure it for both engaged and bypassed modes.
     
  8. peridot1

    peridot1 Member

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    ^That's right. I forgot about that. I think with most of mine the current draw averages around 70% of the max the power supply can do. Give or take.
     

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