Not Sure What Ohm My Head Is?

Discussion in 'Amps [BG]' started by PigsHaveFlown, Jan 4, 2014.


  1. PigsHaveFlown

    PigsHaveFlown

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    Hey everyone, another scrub who doesn't know much about Ohms here,

    I've just come across a Woogie Bass Head (it's an Australian made copy of the Mesa Boogie heads) and the plate with all the details about the amp has been scratched off. Under the two 1/4 inch jacks it tells me that the "total impedance is 4ohms". I want to know if I'm able to use it with my 4ohm cab, does this mean that each input is 8ohms and both inputs equal 4ohms?

    While I'm here I may aswell ask if there is any easy way to tell how much watt my head is, as the plate with the details has been scratched off and each head was custom made so I cannot simply look it up.

    Any light you can shed on my situation will be much appreciated, thanks in advance
     
  2. T-Bird

    T-Bird

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    Hi.

    Welcome to TalkBass PigsHaveFlown.

    The most common way to wire two outputs is to have them in parallel.
    If that's the case here, You can use either two 8Ohm cabs or a single 4Ohm cab, or daisy chained combinations, just as long one jack in use it's 4 Ohm total load and if two jacks are in use it's 8Ohm total load in each jack.

    While that's the most common way, there is others as well.
    Te only sure way is to look inside and perhaps make some measurements.

    If You decide to open 'er up, keep the safety as the first priority.

    Is the manufacturer out of business?

    Regards
    Sam
     
  3. megafiddle

    megafiddle

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  4. PigsHaveFlown

    PigsHaveFlown

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    Thanks T-Bird, long time lurker, first time poster haha.

    So I should have no problems using it with just my 4Ohm cab? (which is a SVT 410HLF btw). The manufacturer is still in business and making them, but its quite a drive away to go see him at his store.

    Megafiddle, problem is I'm not entirely sure that mine is the 100watt tube version, as there are no tubes which I can see without opening it up, and he did make a 400watt model with a tube pre-amp which I believe is what I might have. Or hell, maybe its one of the 1000watt heads he makes, I haven't the slightest clue.
     
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  6. JimmyM

    JimmyM Supporting Member

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    Looks like our guitarist's Mark II, which is a tube amp. Does it have a switch to go between 8 ohms and 4 ohms? Tube amps have different impedance rules than solid state heads, and T-Bird's answer was given assuming it's a solid state. If it has the switch, you're fine. If not, chances are it would be fine running at 4 ohms off just one jack, but you should contact the manufacturer as sometimes impedance mismatches can result in overworking the output transformer and power tubes and lead to an early failure if you run it hard, like if you're going for power tube distortion. You shouldn't have to drive all that way to ask about it, but you should probably ask.
     
  7. beans-on-toast

    beans-on-toast Supporting Member

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    That means that you can plug in one 4 ohm cab or two eight ohm cabs. That's the way, boogie does it, aha aha.

    So I assume Woogie copied that.
     
  8. two fingers

    two fingers Loud Mouth Know It All Blowhard

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    I got nuthin.......

    Except Welcome to TalkBass!
     
  9. T-Bird

    T-Bird

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    Hi.

    You're welcome.

    The 410HLF should be fine.

    Can't You just call the manufacturer or drop him an email, sure he has kept some kind of records of the amps he has made?


    Actually nope, I assumed it's a tube amp without an impedance selector switch.
    That's the reason all the options I gave were 4Ohm in total.
    The "4Ohm total impedance" instead of "4Ohm minimum" supports the amp having a transformer coupled power section as well.
    IME anyway.

    OTOH, I assumed a Mesa Boogie clone to be a tube amp just like I would assume a Fender guitar or a bass clone to be a bolt on ;).

    Regards
    Sam
     
  10. Cirk

    Cirk

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    As long as your chakras are in harmony, aren't all ohms the same? Just wondering. Sorry folks, couldn't resist.
     
  11. JimmyM

    JimmyM Supporting Member

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    Sorry...got some really bad news last night and wasn't thinking hard enough to realize that.
     
  12. T-Bird

    T-Bird

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    Hi.

    No problem Jimmy, no apologies necessary, bad news do distract everyone of us.

    Regards
    Sam
     
  13. PigsHaveFlown

    PigsHaveFlown

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    Thanks for the help everyone,
    Just tried the woogie and the 410HLF together and they worked well, got to the point where my leg hairs where being blown off and there was no problems which I could immediately tell. Can anyone tell me what signs I should be looking for if they where the wrong Ohm for eachother?. I can't comment on the sound as my house is haunted by a terrible feedback demon that nomatter where I go in the house I will get terrible static noise, but everything works fine anywhere else. I need a sound engineer to perform some kind of exorcism on my house it seems,
     
  14. beans-on-toast

    beans-on-toast Supporting Member

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    You can't really tell if there is an impedance mismatch by listening. A cab can be measured with an ohm meter. There are ways for a tech to determine what the impedance taps are on an output transformer but it would be easier to contact the builder and ask. If you are lucky, the transformer is labeled but that usually isn't the case.

    The noise at home could be caused by a lot go different things such as bad wiring, fluorescent lighting, fridge, heater, or air conditioner motors, a bad transformer out in the street, a local ham radio operator, etc.....
     
  15. PigsHaveFlown

    PigsHaveFlown

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    It would probably be best to send a message to the manufacturer then I guess, I'm not gain enough to open it up because I have a tendency to do that and forget how to put things back together. Its seems the feedback ghost is here to stay then ahah
     

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