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do i need to bias my 5150 for a re-tube?

Discussion in 'Backline' started by Incognito Man, Aug 14, 2011.

  1. Incognito Man

    Incognito Man Member

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    its time for new tubes in my 5150 and i have never done this before so i dont know much about it.

    do i need to bias the head or can i just put the tubes in and be on my way?

    on the eurotubes site it says the tube kit is "plug and play" so i assume this means i do not need to bias.

    also it says to put a speific tube in "v1" what position is v1?

    the head is an older model with eddies signature on the back and it just says "EVH" in bold black letters on the front.

    thanks!
     
  2. greyskull

    greyskull Member

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    5150s unless modded are fixed Bias... so no.
     
  3. Incognito Man

    Incognito Man Member

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    awesome! then i dont need to pay a tech and have downtime.
     
  4. Incognito Man

    Incognito Man Member

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    i just found this info on the net so perhaps i will have to take it in.



    "Fixed bias does not mean that the amp "biases itself". It means that the voltage to bias the amp is a fixed one, which is usually adjustable (or, should be) so that the amp can be biased properly for each new set of tubes"
     
  5. Wohma

    Wohma Hearing sounds and voices

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    V1 is a position in the preamp (12AX7 tubes, the smaller ones). These can be changed without any adjustments. Replacing power tubes usually requires settings the bias. Although you theoretically could just swap the tubes and play without problems, you could also fry not only the tubes, but potentially also some parts of the amp - and you probably don't want to do that. If you're investing into complete retubing, add a few more bucks and have someone reliable and experienced do that. Better safe than sorry.
     
  6. TheWinterSnow

    TheWinterSnow Den Mørke Natt

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    That's not what fixed bias means.

    EDIT: I got beat to the punchline.


    5150s are biased extremely cold and are not adjustable without a mod, so unless you want to pay for a bias mod (or you can DIY) then you don't need to worry about it. FWIW, I did the bias mod on mine, but its not something everyone likes.
     
  7. acappa

    acappa Alex Cappa TMF Studios

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    Peaveys amps are biased cold, at least XXX and 6505. Is the 6505 II fixed bias too??? I need to retube very soon...
     
  8. acappa

    acappa Alex Cappa TMF Studios

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    Are you retubing the same way as the standar? 5x12AX7 + 4x6L6 ?? May be I´m trying some KT77...
     
  9. TheWinterSnow

    TheWinterSnow Den Mørke Natt

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    All high gain metal amps have fixed biased power amps.

    Wouldn't recommend anything other than 6L6s unless you want your amp to die on you.
     
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  10. stilllifer

    stilllifer Member

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    V1 preamp is usually the closest one to the input.
     
  11. Damage, Inc.

    Damage, Inc. Member

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    Bob from Eurotubes recommends fairly hot tubes to offset the cold bias of amps like Mesa and Peavey. Your tube life will be somewhat shorter than the stock ones, but your amp should sound better. You're not going to hurt the amp by doing this. Remember that fixed bias means there is either a resistor or a pot that sets the bias. For the 5150, setting the bias means swapping the resistor...not worth the effort if you have the right tubes.
     
  12. bryan_kilco

    bryan_kilco Member

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    I semi-recently swapped out Groove Tubes (power) and Sovtek (pre) from my Mesa Mark IV and replaced them with a Doug's Tubes set of Ruby 6L6/EL34 and the 12ax7 preamp kit. This retube made the amp SOOOO much LOUDER!! I can barely push it to 2 on the master volume without drowning out the band.
     
  13. Incognito Man

    Incognito Man Member

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  14. bryan_kilco

    bryan_kilco Member

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    If it makes you feel any better, our other guitarist retubed his Recto with a High Gain kit from Eurotubes and he didnt re-bias. I retubed my Mark IV and didnt get it biased. They claimed the tubes were picked based on the type of amp you use......
     
  15. CraigCabana73

    CraigCabana73 New Metal Member

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  16. atoragon

    atoragon Member

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    that's not exactly true, there are some in which you can use different power tubes and they will set the bias accordingly, such as the hughes and kettner switchblade, coreblade etc
     

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