Marshall 2210 Clipping Diodes Questions

Discussion in 'The Workbench' started by Veri-mu, Jan 10, 2017.

  1. Veri-mu

    Veri-mu New Member

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    Hello my name is Alex,

    I have a 2210 from the year 1987 this is the schematic

    http://www.pierluigipollano.ilbello.com/Resources/Schemi_Marshall/JCM 800 2210 Pre.gif

    My questions are regarding two diodes within the V1b section of the overdrive channel D1 and D6. D1 is located where a cathode bypass capacitor would normally exist within V1b. It is parallel to the existing 10k cathode resistor(R3 on the schematic). D6 is located below and connected to the rectifier bridge (WOO5 on the schematic) downstream from V1b.

    I will begin with D6.

    If I change, the stock diode (D6) from a 1N4007 that has .6v forward voltage to a LED diode with a higher voltage drop, would I be able to move the threshold of the clipping to turn on later? This would mean I would be able to tune the bridge rectifier (W005) similar to a threshold nob on a compressor/limiter. With a lower voltage drop I would have more clipping and less of the true signal passing and the opposite with a higher voltage drop. Am I correct?

    D1 question

    This question is similar to the first regarding the tuning ability of this diode. D1 is a 1N4007.

    I am assuming that D1 creates a fully bypassed cathode when the negative feedback (cathode degeneration) reaches the forward voltage of the 1N4007. If I am correct, A LED diode would bypass less often as it needs more voltage to open.

    Is it possible to make the transition between unbypassed to full bypass smooth by tuning the voltage drop? For example switching between germanium, silicone, and LED.
     
  2. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Yes, LED will increase the voltage drop level.
    At D6 a higher voltage drop will cause the clipping circuit to not clip as low but still clip.
    At D1 the diode acts more as limiter for the cathode voltage, not a clipper. A higher voltage drop will help reduce gain/output of the stage.
     
  3. Veri-mu

    Veri-mu New Member

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    Thanks for the info it is appreciated
     
  4. ampmadscientist

    ampmadscientist Well-Known Member

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    In your bathtub.
    It already is a compressor limiter...
    Changing to LED will alter the tonal quality but the difference between .7V and 1.2V (before compression) is not the deciding factor.
     

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