New dsl100h tube choice and biasing

Discussion in 'The Workbench' started by glprich, Jan 6, 2020.

  1. glprich

    glprich Member

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    Looking for tubes closest to the originals that come new with the amp, and biasing voltage keep in mind this is the new dsl100h, thanks!!
     
  2. Lance Chambers

    Lance Chambers Well-Known Member

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    :welcome:

    What year model is your amp?:photos:
     
  3. South Park

    South Park Well-Known Member

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    You may not have to bias the amp . Set by the factory . Lots of tubes set out thar . Plug em in and jam it
     
  4. glprich

    glprich Member

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    What I meant by new was it's not a jmc2000, I'm not 100% sure what the year model it is I know I bought it used and have had it for several years
     
  5. ampmadscientist

    ampmadscientist Well-Known Member

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    If it's a DSL 100h, it's a JCM 2000.
     
  6. mcblink

    mcblink Well-Known Member

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    :orly:

    76DSL100H.jpg


    marshall-jcm-2000-dsl1001.jpg
     
    Michael Roe likes this.
  7. mcblink

    mcblink Well-Known Member

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    Check the S/N on the label with the barcode on the back side of the head for date of manufacture, for example:


    10-Letter_gldyiq.jpg
     
  8. Matt_Krush

    Matt_Krush Well-Known Member

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    Preamp Tubes:
    If red Marshall labels, they are JJ
    If white Marshall labels, Chinese made (Shuguang)

    Power Tubes could be either JJ or Tung sol.
    If JJ now, I recommend using the Tung Sol EL34Bs instead. The JJs sound good, but the Tung Sols sound much 'bigger' and fuller.

    Bias is determined by the plate voltage and current draw of the tubes while in place, or use a scope if available.
    Power Tubes are not just drop in and play (pre-amp tubes are).
     
  9. Michael Roe

    Michael Roe Well-Known Member

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    Take a clear pic of the tubes and post it hear and we can probably tell you what they are.
    If you bought it used it could have something other than original in it.
    Most newer Marshalls come with JJs.
    BTW, the DSL 100H is in between the JCM 2000 DSL and the newest DSL 100HR.
    Essentially, the DSL 100H is a an Asian made copy of the JCM 2000 DSL. I have never compared them side by side but from what I have heard is that the DSL 100H has different transformers in it. I could be wrong on this so don't hold me too it :)
    The "HR" version is a Vietnam made one that has a few extra features and is voiced different than the 2K.
     
  10. glprich

    glprich Member

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    So more often do the preamp tubes go bad or the power tubes, whats your recomendation for pre amp tubes?
     
  11. glprich

    glprich Member

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    The one think
    which would be your choice
    Tung-Sol 12AX7 New Production Preamp Vacuum Tube
    or
    Tung-Sol ECC803s 12AX7 Gold Pin Preamp Vacuum Tube
     
  12. glprich

    glprich Member

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    Both my DSL heads are packed for the next show, i got in the trailer and tried to look and it looks like all writing is white and all tubes in both heads look like they have the Marshall logo on them, the one in question is a 2012 model, the other is a 2015
     
  13. Matt_Krush

    Matt_Krush Well-Known Member

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    Buy a mix of preamp tubes.
    Each one can bring changes you may or may not like.

    I run a mix of:
    JJ ECC 803: V1, Phase Inverter
    Sovtek LPS: V1, phase inverter
    Tung Sol: V1,V2
    Shuguang: Wherever the tone stack is
    JJ 12AX7: any spot

    Marshalls to me, tend to favor JJ preamp tubes as Tung Sold, EH, can be a bit too bright.
    Again, try them and see what you like.
    I have 4 Marshalls, those are the tubes I use, but not always in the same locations on each amp.
    I do run both JJ KT77s and Tung Sol EL34s in different amps.
     
    Last edited: Jan 7, 2020
  14. glprich

    glprich Member

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    So using the plate voltage what is the formula to determine bias VOLTAGE?
     
  15. Matt_Krush

    Matt_Krush Well-Known Member

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    This gets ya in the ball park quickly.
    Tube Wattage/Plate Voltage x .7 = I (in amps...multiply by 1000 for mA)

    or...
    https://www.amplifiedparts.com/tech-articles/tube-amplifier-bias-calculator

    Use to be power tubes went bad more often than preamp tubes....now a days...it can be a crap shoot...I mean, they are either built in Russia, China or Slovakia...not exactly the world leaders of manufacturing things that last. As a General rule, power tubes get worked the hardest, get the hottest and do die off sooner than preamp tubes.

    Your original post says you want to remain...stock-ish.
    Thats a tough one as Marshall never uses the same manufacturer year to year, model to model...and some are no longer in existence.

    MArshall uses Tung Sol and JJ EL34's on the current offerings.
    GO WITH TUNG SOL EL34Bs.

    Preamp tubes...if they are 'red labeled marshalls...they are JJ12AX7s
    If they are white Label Marshalls, they are a china brand (Sino or Shuguang).

    Now...different preamp tubes will alter the tone.
    Is there something you are looking to enhance? Treble, Bottom end, mids, distortion, clean up fizziness, reduce distortion?

    Me, I'd go
    V1= JJ803
    V2 = Tung sol 12AX7
    V3 = Shuguang
    V4 = Sovtek LPS

    And Tung Sol EL34 for output.
     
  16. glprich

    glprich Member

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    that gives you mA, Im looking to bias by the 3 pin connector and using the 2 Trim pots i believe thats a mV value?
    Like in this video
     
  17. Matt_Krush

    Matt_Krush Well-Known Member

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    Didn't watch video, but if you're talking about the 3 pins Marshall has inside the amp, then yes, you are measuring mV.
    That circuit has a 1ohm resistor that you are measuring across.
    The V=IR formula...Ohms Law...If R =1ohm, then V=I.
    So while you are reading/measuring mV, you also measuring mA in this instance due to Ohms Law.
     
  18. glprich

    glprich Member

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    lol makes since, I saw a video where they removed the ground wire to add a 1 ohm resistor to read Voltage drop thanks for the info!!!
     
  19. mickeydg5

    mickeydg5 Well-Known Member

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    People really should not start 15 threads concerning the same subject. :squint:
     
  20. mickeydg5

    mickeydg5 Well-Known Member

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    Wrong.
     

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