Using a Lead 100 Mosfet w/o Speakers?

Discussion in 'The Workbench' started by Mark Diehl, Aug 13, 2013.

  1. Mark Diehl

    Mark Diehl New Member

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    I recently purchased a Lead 100 Mosfet. I would like to use this in an electric/acoustic duo I am part of WITHOUT speakers, running it straight into our PA mixing board out of the DI.

    I know this is a big No-No in the tube amp world, but would this be okay with this head?

    Thanks!

    Mark
     
  2. MKB

    MKB Well-Known Member

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    Probably it is OK. In general, with amps that have no output transformer, they simply do not care if there is no load. Such an amp will then only swing voltage, no load = no current and thus no power from the amp.

    I would suggest you check the manual for the amp. If there is no minimum recommended load, and no warning about having a speaker connected, it should be safe to operate it with no speaker.
     
  3. mott555

    mott555 Well-Known Member

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    Running without a load ought to be okay on solid-state amps.
     
  4. chuckharmonjr

    chuckharmonjr Well-Known Member

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    No speaker "load" on a solid state output section is no problem at all. Since it is an open circuit, that represents infinite load and therefore no current flow at all.
     
  5. MKB

    MKB Well-Known Member

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    There are some solid state amps (such as very early ones and current McIntosh stereo amps) with output transformers, and those may not react well to running without a load. So it is best to check to be 100% sure. However I am almost 100% sure that the Mosfet 100 does not have an OT and is safe to use without a load.
     
  6. plec-2

    plec-2 New Member

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    Yes it's ok to run mosfet/transistor amp with out load..plus that model has a line feed out that switches the pre-amp form main power amp via the jack socket and floats the signal from the amp.
     
  7. MoreZazz

    MoreZazz New Member

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    Thank y'all for this thread! It's my solution to fix my 5213 MOSFET twins problems! Tytytyty!
     
  8. RickyLee

    RickyLee Well-Known Member VIP Member

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    Very odd thread.

    I am repairing an AVT50 that blew the output IC after the previous owner had the speaker cable yanked out while playing it. Smoked the IC chip as well as a 10 ohm resistor on the PCB that is part of the output section as well.

    :hmm:
     
  9. hazmat7719

    hazmat7719 Active Member

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    RickyLee,
    The amp could have been diving a direct short when the cable was yanked out. The connector could have shorted both contacts for a brief time.
     
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  10. Ken

    Ken Well-Known Member

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    Exactly. There was a momentary short and with a SS amp that's all it takes.

    Ken
     
    hazmat7719 likes this.
  11. RickyLee

    RickyLee Well-Known Member VIP Member

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    Interesting for sure. I just can't get myself to trust running even my solid state amps without a load. I was thinking of running FX out of the MOSFET into another amp as well. But then I was going to have a speaker load on the MOSFET regardless.

    I thought of another situation that was similar to the damaged AVT50. Many years ago my vocalist' Carvin PA blew one of the power amp IC's on one channel. That one was from an OPEN on the 1/4" jacks on the PA speaker cab. That scenario is similar to what you guys are stating except there was no momentary direct short as the speaker cable came out on the speaker side not the amp side. I see how you guys are stating that the scenario on my AVT50 was a momentary short from the action of the speaker cable coming out of the amps speaker out jack while powered on. But the Carvin scenario was a load to no load action, no direct short.
     
  12. dsn716

    dsn716 Active Member

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  13. Masteresgt

    Masteresgt Active Member

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    I blew my 2 IC with speakers cables retracted from the socket of the cab (a modified Yamaha B212 amp with speaker socket added to use the amp as cab only)... I think that tip of cable touch the ground of the socket when retracted so cable was short.

    Wanged unplugged cables must not "short" the output unless they touch a ground somewhere...
     
  14. anitoli

    anitoli Well-Known Member

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    The manual states to never power up the head without a speaker, so do so at your own risk. Besides as was already posted the head has a DI out put.
     

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