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techie ?s -- volts, watts, etc.

Discussion in 'Amps and Cabs [BG]' started by jondog, Mar 7, 2003.


  1. jondog

    jondog

    Mar 14, 2002
    NYC metro area
    Hi, I'm having a petty argument w/ a tech support person and want to get my facts straight. Please help if you know the answers to these questions. I put this in amps because this is where most of the tech people seem to be.

    What is the difference between voltage and amperage?

    Will adapters whose voltage is too high *safely* power lower voltage devices? (18v wart for 9v pedal)?

    What are the equations for power? Watts = ?
    volts = ? amperage = ?

    Thanks!
     
  2. What is the difference between voltage and amperage?

    Voltage is electromotive force or potential difference, analogous to pressure in a water hose. It tells you how badly the electrons want to move. Current is the actual flow of electrons measured in Amps, analogous to gallons per minute flow rate in a hose. This is a quantity of electrons flowing by per second. 1 Amp = 1 Coulomb of charge per second to be exact.


    Will adapters whose voltage is too high *safely* power lower voltage devices? (18v wart for 9v pedal)?

    No. Putting too high a voltage into a device will most likely blow the power supply capacitors, and maybe a few chips. You can fudge a little bit, like putting 10V into a 9V device, but I wouldn't put 18V into a 9V device.

    What are the equations for power? Watts = ?
    volts = ? amperage = ?

    P=IV
    V=IR
    Those are the only 2 equations you need. You can rearrange and substitute to get Power in terms of I and R or V and R. P=power, V=voltage, I=current, R= resistance

    Chris
     
  3. To add to what Chris said, if you have an adaptor at the right voltage that can supply more current than you need it's OK because the device will only draw the current it needs from the adaptor
     
  4. jondog

    jondog

    Mar 14, 2002
    NYC metro area
    Thanks! You guys rock! Fast detailed responses. I'm wondering if these tech support people get any training at all!
     
  5. jondog

    jondog

    Mar 14, 2002
    NYC metro area
    Joris, your tech FAQ is awesome! I read it when I first joined TB and you've added lots more great info since then.

    It doesn't really define voltage or current though, it just says that I have to have voltage in order for current to flow. Also, it doesn't answer my question about 18v adapters working on 9v gear.

    Maybe you could add definitions and a water analogy like throbbinnut gave me?

    Also maybe you could add a practical questions section, like what happens when I put 18v through a 9v system? Or in the cable section, what am I really risking by using standard 1/4" cable instead of balanced over short runs?

    I'm not trying to slam your document, it really is the best resource of its kind I've seen. It's just that it was written by a very technically adept person, who might not realize that non-techie readers don't have a definition for voltage etc. in the first place.
     
  6. knight

    knight

    Nov 3, 2002
    I have a related question! How about the opposite of what was asked above, that is, can you run 18V to a device that requires 24V? My EHX synth should ideally run on 24, but my dc brick provides 18. I have plugged it in and it works fine, any short- or long-term problems with this?

    Thanks!
     
  7. It should work Ok but you'd get less headroom. There aren't any maintenance issues that I know about with supplying a lower than rated voltage. It will either work or it won't;)
     
  8. knight

    knight

    Nov 3, 2002
    Thanks Mark, I was just worried that the synth might explode or ignite killing me and everyone in a 30 ft range, but it it's safe I'll go ahead, after all it works just fine... cheers