Mosfet vs. diodes for OD/Boost?

Discussion in 'Effects, Pedals, Strings & Things' started by Winklin, Dec 15, 2005.


  1. Winklin

    Winklin Member

    Messages:
    214
    Joined:
    Dec 29, 2004
    Can anyone describe the general difference in tone, feel, gain structure or whatever between OD/Boost pedals that use diodes and ones that use mosfet tech to generate clipping?
    Looking for a little enlightenment......
    Thanks.
     
  2. wopr

    wopr Member

    Messages:
    391
    Joined:
    Jul 8, 2005
    Bump. I'd like to know as well. I also saw something called "Cascaded, non-inverted gain stages" (pro-analog). How is that different?
     
  3. Marcus Dahl

    Marcus Dahl Member

    Messages:
    69
    Joined:
    Nov 18, 2005
    Location:
    White Co., TN
    Germanium diodes are more compressed and squishy sounding
    Silicon diodes are sharp focused and tight
    Fets/Mosfet transistors are tubish and crunchy
    LEDs are crunchy buzzy and less compressed

    Cascading is like it sounds. It's something that is in series with or one right aftrer the other. You can do this with diodes, transistors, op-amps. Just about anything.

    Non-inverting gain stages. You have an in-verting and a non-inverting side on on an op-amp. You can just use one or the other as inputs or to control your gain.
     
  4. StompBoxBlues

    StompBoxBlues Member

    Messages:
    18,587
    Joined:
    Sep 20, 2005
    Location:
    under the stars
    Good answer. Just to elaborate, cascading is more specifically that amplifiers (op-amps, or transistors, or tubes) amplify and pass the amplified signal on to another amplification stage...it means more control because each stage then can stay more in its' boundaries of operation. I mean, instead of one amplification stage, where it is pushing it's limits, it can work less hard...amplify a little less and pass it on to another that can also have more headroom, etc.
     
  5. StompBoxBlues

    StompBoxBlues Member

    Messages:
    18,587
    Joined:
    Sep 20, 2005
    Location:
    under the stars
    By the way...did you mean that about LEDs being less compressed?
    I was surprised, because to me...they act as diodes that drop 0.7 (am I misremembering?) which would mean any voltage rising above 0.7v in the correct orientation, will clip immidiately after that point (unless there is a resistance in series that will move up the clip point) which would make me think it would be more compressed?

    How come they are less compressed?
     
  6. Marcus Dahl

    Marcus Dahl Member

    Messages:
    69
    Joined:
    Nov 18, 2005
    Location:
    White Co., TN
    Good question. I go mainly by my ears on this stuff. So I'm less technical than some of the other builders, but if memory servce me right. Silicon is .6v & germainium is like half, or round about. I would say that LEDs being less compressed would be from what materials they use to make them. I'm not sure what they measure, but from my experience with them they are less compressed sounding. Of course this changes some from color to color as well as the tone and even the clipping threshold.
     
  7. Don Rusk

    Don Rusk Gold Supporting Member

    Messages:
    6,879
    Joined:
    Jul 22, 2002
    Location:
    St. Louis
    Right I thought LEDs as clipping diodes generally had more 'headroom'/higher clipping ceiling than 'regular' diodes ---

    usually on pedals with diode or 'compression' switches - the regular diodes are the most clipped/compressed - LEDs for less compression and no diodes for least compression...
     
  8. Marcus Dahl

    Marcus Dahl Member

    Messages:
    69
    Joined:
    Nov 18, 2005
    Location:
    White Co., TN
    Transistor - depends
    Germanium - Most Compression
    Silicon- less
    LED's - even less
    Nothing - depends on the circuit.

    Remember overdrive and distortion is a type of compression.
     
  9. Marcus Dahl

    Marcus Dahl Member

    Messages:
    69
    Joined:
    Nov 18, 2005
    Location:
    White Co., TN
    Finally somebody with a more eloquent writing skill than I, and he is right.
     
  10. Don Rusk

    Don Rusk Gold Supporting Member

    Messages:
    6,879
    Joined:
    Jul 22, 2002
    Location:
    St. Louis

    Compression is also a form of distortion - distortion meaning 'change or alteration' ~~ compression is amplitude distortion.
     
  11. Marcus Dahl

    Marcus Dahl Member

    Messages:
    69
    Joined:
    Nov 18, 2005
    Location:
    White Co., TN
    :AOK
     

Share This Page